WO1999038975A2 - Polynucleotide and polypeptide sequences associated with cns depressant sensitivity and methods of use thereof - Google Patents

Abstract

The invention provides polynucleotide and polypeptide sequences associated with CNS depressant sensitivity, and methods for identifying and classifying candidate CNS depressants as well as methods to identify agents which may modulate CNS depressant action. The invention also provides mouse mGluR5 polynucleotide and polypeptide sequences.

Description

POLYNUCLEOTIDE AND POLYPEPTIDE SEQUENCES ASSOCIATED WITH CNS DEPRESSANT SENSITIVITY AND METHODS OF USE THEREOF

CROSS-REFERENCE TO RELATED APPLICATIONS This application claims the priority benefit of U.S. Provisional Patent Application

No. 60/073,190, filed January 30, 1998. The priority application is hereby incorporated herein by reference in its entirety.

STATEMENT OF RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSORED RESEARCH

This invention was made in part during work supported by grants from the National Institutes of Health (NIH) NIAAA RO1-AA08940 and NIGMS RO1-GM55635. The government has certain rights in this invention.

TECHNICAL FIELD

This invention relates to polynucleotide and polypeptide sequences associated with CNS depressant sensitivity, as well as methods using these sequences.

BACKGROUND ART Central nervous system (CNS) depressants have been used for a variety of purposes, including anesthesia. CNS depressants are also socially, economically and medically significant in terms of drug use and abuse, sueh as ethanol, barbituate, and sedative consumption. While several useful anesthetics have been developed, such as propofol, improved anesthetics are still needed. Furthermore, the basis of propensity toward excess ethanol consumption, or differential sensitivity toward this and other CNS depressants, is still not known.

Several animal models have been used to study the basis of CNS depressant action. Simpson and Johnson (1996) Int. Rev. Neurobiol. 39:223-241. LS (long sleep) and SS (short sleep) mice were initially selected on the basis of differential ethanol sensitivity. Simpson and Johnson (1996); McClearn and Kakihana (1981) "Development of Animal

Models as Pharmacogentic Tools", McClearn et al, eds, Research Monograph No. 6 at 147- 159 (U.S. Dept. Health Human Services). In addition to ethanol, the LS and SS mice are differentially sensitive to a variety of other agents having properties of CNS depressants. Simpson et al. (1996) Anesth. Analg. 82:1-5; Markel et al. (1996) Mam. Genome 7:408- 412; Simpson and Johnson (1996). These CNS depressants include chloral hydrate, enflurane, etomidate, flurazepam, halogenated ethanols, isoflurane, ketamine, midazolam, paraldehyde, MK-801, urethane and propofol. These agents have diverse chemical structures suggesting that the LS and SS mice have been selected, at least in part, for genes that influence sensitivity to multiple classes of CNS depressants. However, LS and SS mice do not differ in sensitivity to ether or halothane, (Baker et al. (1980) Pharmacol. Biochem. and Behav. 12:691-695), indicating that there has not been uniform selection for differential sensitivity to all anesthetic agents.

LS and SS mice exhibit significant CNS differences in their sensitivity to propofol- induced anesthesia. Simpson and Blednov (1996) Anesth. Analg. 82:327-331. Given the same 20 mg/kg dose via the retroorbital sinus, SS mice slept about 3.5 minutes (SEM = 0.4 min) and LS mice slept about 2.2 minutes longer, with no difference between males and females. Moreover, although propofol has a potent effect on GABA_A receptors, (Tanelian et al. (1993) Anesthesiology 18:151-116), LS and SS mice did not exhibit significant differences in GABA_A-activated chloride channels. However, the genetic locus contributing to this differential sensitivity has not been discovered.

The metabotropic glutamate receptors (mGluRs) are G protein-coupled receptors capable of activating a variety of intracellular second messenger systems following the binding of glutamate or other potent agonists including quisqualate and 1 - aminocyclopentane-l,3-dicarboxylic acid (trans-A PO). Schoepp et al. (1990) Trends Pharmacol. Sci. 11:508; Schoepp and Conn (1993) Trends Pharmacol. Sci. 14:13.

Activation of different metabotropic glutamate receptor subtypes in situ elicits one or more of the following responses: activation of phospholipase C, increases in phosphoinositide (PI) hydrolysis, intracellular calcium release, activation of phospholipase D, activation or inhibition of adenylyl cyclase, increases and decreases in the formation of cyclic adenosine monophosphate (cAMP), activation of guanylyl cyclase, increases in the formation of cyclic guanosine monophosphate (cGMP), activation of phospholipase A₂, increases in arachidonic acid release, and increases or decreases in the activity of voltage- and ligand-gated ion channels (Schoepp and Conn (1993); Schoepp (1994) Neurochem. Int. 24:439; Pin and Duvoisin (1995) Neuropharmacology 34:1). Thus far, eight distinct mGluR subtypes have been isolated via molecular cloning, and named mGluRl to mGluR8 according to the order in which they were discovered. See, for example, Nakanishi (1994) Neuron 13:1031; Pin and Duvoisin (1995) Neuropharmacology 34:1; Knopfel et al. (1995) J. Med. Chem.. 38:1417. Further diversity occurs through the expression of alternatively spliced forms of certain mGluR subtypes.

Pin et al. (1992) Proc. Natl. Acad. Sci. 89:10331; Minakami et al. (1994) BBRC 199:1136. All of the mGluRs appear to be structurally similar, in that they are proposed to be single subunit membrane proteins possessing a large amino-terminal extracellular domain (ECD) followed by seven putative transmembrane domain (7TMD) comprising seven putative membrane spanning helices connected by three intracellular and three extracellular loops, and an intracellular carboxy-terminal domain of variable length (cytoplasmic tail) (CT). The eight mGluR subtypes have unique patterns of expression within the mammalian CNS that in many instances are overlapping. Masu et al. (1991) Nature 349:760; Martin et al. (1992) Neuron 9:259; Ohishi et al. (1993) Neurosci, 53:1009; Tanabe et al. (1993) J. Neurosci. 13:1372; Ohishi et al. (1994) Neuron 13:55; Abe et al. (1992) J. Biol. Chem.

267:13361; Nakajima et al. (1993) J. Biol. Chem. 267:13361; Nakajima et al. (1993) J. Biol. Chem. 268: 11868; Okamoto et al. (1994) J. Biol. Chem.269Λ231 ; Duvoisin et al. (1995) J. Neurosci. 15:3075.

The eight mGluRs have been subdivided into three groups based on amino acid sequence identities, the second messenger systems they utilize, and pharmacological characteristics. Nakanishi ( 1994) Neuron 13 : 1031 ; Pine and Duvoisin ( 1995) Neuropharmacology 34:1; Knopfel et al. (1995) J. Med. Chem. 38:1417.

The Group I mGluRs comprise mGluRl, mGluR5 and their alternatively spliced variants. The binding of agonists to these receptors results in the activation of phospholipase C and the subsequent mobilization of intracellular calcium. For example,

Xenopus oocytes expressing recombinant mGluRl receptors have been utilized to demonstrate this effect indirectly by electrophysiological means. Masu et al. (1991); Pin et al. (1992). Similar results were achieved with oocytes expressing recombinant mGluR5 receptors. Abe et al. (1992); Minakami et al. (1994). Alternatively, agonist activation of recombinant mGluRl receptors expressed in Chinese hamster ovary (CHO) cells stimulated

PI hydrolysis, cAMP formation, and arachidonic acid release as measured by standard biochemical assays. Aramori and Nakanishi (1992) Neuron 8:757. In comparison, activation of mGluR5 receptors expressed in CHO cells stimulated PI hydrolysis and subsequent intracellular calcium transients but no stimulation of cAMP formation or arachidonic acid release was observed. Abe et al (1991).

The Group II mGluRs include mGluR2 and mGluR3. Activation of these receptors as expressed in CHO cells inhibits adenylyl cyclase activity via the inhibitory G protein, Gi, in a pertussis toxin-sensitive fashion. Tanabe et al. (1992) Neuron 8:169; Tanabe et al. (1993).

The Group III mGluRs include mGluR4, mGluRό, mGluR7 and mGluR8. Like the Group II receptors these mGluRs are negatively coupled to adenylate cyclase to inhibit intracellular cAMP accumulation in a pertussis toxin-sensitive fashion when expressed in

CHO cells (Tanabe et al. (1993); Nakajima et al.(1993); Okamoto et al. (1994); Duvoisin et al. (1995).

Several reports indicate that various mGluRs may be affected by various anesthetics. See, e.g., Dildy-Mayfield et al. (1996) J Pharmacol. Exp. Ther. 276:1058- 1065 (describing experiments addressing the effect of various anesthetics on certain mGluRs, but not mGluR5); Orser et al. (1995) Br. J. Pharmacol. 116:1761-1768 (describing experiments addressing inhibition by propofol of N-methyl-D-aspartate subtype of glutamate receptor); Miyamoto et al. (1994) Eur. J. Pharmacol. 260:99-102 (describing experiments addressing delay in recorery from halothane anesthesis by agonists for metabotropic glutamate receptors).

Nucleic acids encoding human metabotropic glutamate receptors mGluRl , mGluR2, mGluR3 and mGluR5 are described in U.S. Pat. 5,521,297. See also U.S. Pat. 5,202,257. Human mGluR5 is cloned and characterized by Minakami et al. (1994) Biochem. Biophys. Res. Comm. 199:1136-1143. Rat mGluRs polynucleotide and polypeptide sequences are described in Abe et al. (1992). See also Minakami et al. (1993)

Biochem. Biophys. Res. Comm. 194:622-627. The 550 base nucleotide sequence containing a single exon (of about 100 nucleotides) of mouse mGluR5 has been reported. Minakami et al. (1995) J. Neurochem. 65:1536-1542.

There is a continuing need to develop new CNS depressants, particularly anesthetics, which exert fewer side effects. A defined molecular target may allow thedesign of anesthetics which act specifically at neural tissue, thus avioiding side effects related to non-specific actions at other organ systems. There is also a need to refine and/or modulate the action of anesthetics, particularly in certain individuals, such as at-risk individuals.

All references cited herein are incorporated by reference in their entirety.

DISCLOSURE OF THE INVENTION

The present invention provides methods using polynucleotide and polypeptide sequences associated with CNS sensitivity, as well as the polynucleotide and polypeptide sequences themselves. In particular, these methods are used to identify, inter alia, agents which may exhibit CNS depressant activity and/or modulate CNS depressant activity. Accordingly, in one aspect, the invention provides a method for identifying an agent which may exhibit CNS depressant activity, comprising the steps of: (a) introducing a polynucleotide comprising a mouse polynucleotide sequence associated with CNS depressant sensitivity into a suitable host cell, wherein the mouse polynucleotide sequence corresponds to a polynucleotide sequence of yeast artificial chromosome YRT2; (b) contacting host cell of step (a) with at least one agent to be tested; and (c) analyzing at least one characteristic associated with expression of the mouse YRT2 polynucleotide, wherein an agent is identified by its ability to modulate expression of the mouse YRT2 polynucleotide.

In another aspect, the invention provides a method of classifying a CNS depressant, comprising the steps of: (a) introducing a polynucleotide comprising a mouse polynucleotide sequence associated with CNS depressant sensitivity into a suitable host cell, wherein the mouse polynucleotide sequence corresponds to a polynucleotide sequence of yeast artificial chromosome YRT2; (b) contacting host cell of step (a) with at least one agent to be tested; (c) analyzing at least one characteristic associated with expression of the mouse YRT2 polynucleotide, wherein an agent is identified by its ability to modulate expression of the mouse YRT2 polynucleotide, and wherein a CNS depressant which modulates expression may fall within a class of CNS depressants which displays differential reactivity in LS and SS mice.

In another aspect, the invention provides a method of identifying an agent which may modulate CNS depressant sensitivity in an individual, said method comprising: (a) introducing a polynucleotide comprising a mouse polynucleotide sequence associated with CNS depressant sensitivity into a suitable host cell, wherein the mouse polynucleotide sequence corresponds to a polynucleotide sequence of yeast artificial chromosome YRT2; (b) contacting host cell of (a) with at least one agent to be tested; and (c) analyzing at least one characteristic associated with expression of the mouse YRT2 polynucleotide, wherein an agent is identified by its ability to modulate expression of the mouse YRT2 polynucleotide.

In another aspect, the invention provides a method of identifying an agent which may exhibit CNS depressant activity, comprising the steps of: (a) introducing a polynucleotide comprising a metabotropic glutamate receptor polynucleotide sequence into a suitable host cell; (b) contacting host cell of step (a) with at least one agent to be tested; (c) analyze at least one characteristic associated with expression of the metabotropic glutamate receptor polynucleotide, wherein an agent is identified by its ability to modulate expression of the mammalian metabotropic glutamate receptor polynucleotide. The metabotropic glutamate receptor may be mammalian.

In another aspect, the invention provides a method of classifying a CNS depressant, comprising the steps of: (a) introducing a polynucleotide comprising a mammalian metabotropic glutamate receptor polynucleotide sequence into a suitable host cell; (b) contacting host cell of step (a) with at least one agent to be tested; (c) analyzing at least one characteristic associated with expression of the metabotropic glutamate receptor polynucleotide, wherein an agent is identified by its ability to modulate expression of the metabotropic glutamate receptor polynucleotide sequence, wherein a CNS depressant which modulates the metabotropic glutamate receptor polynucleotide expression may fall within a class of CNS depressants which displays differential reactivity in LS and SS mice.

In another aspect, the invention provides an isolated polynucleotide comprising a polynucleotide encoding a mouse mGluR5 polypeptide, wherein the mouse mGluR5 polypeptide is at least 10 contiguous amino acids of SEQ ID NO:2 and exhibits mGluR5 activity, and wherein the at least 10 contiguous amino acids are not depicted in SEQ ID NO:6 or SEQ ID NO:7.

In another aspect, the invention provides an isolated polynucleotide comprising a polynucleotide of at least about 25 contiguous nucleotides of SEQ ID NO:l, wherein the at least about 25 contiguous nucleotides are not depicted in SEQ ID NO:3 or SEQ ID NO:5.

In another aspect, the invention provides a polynucleotide comprising a region of at least 25 contiguous nucleic acids of SEQ ID NO:l, said region having at least about 97% sequence identity to a sequence in SEQ ID NO: 1. The region is not depicted in SEQ NO:3 or SEQ ID NO:5.

In another aspect, the invention provides an isolated polypeptide comprising at least about 5 contiguous amino acids of the sequence of SEQ ID NO:2, wherein the isolated polypeptide exhibits an mGluR5 function, and wherein the about 5 contiguous amino acids are not depicted in SEQ ID NO:6 or SEQ ID NO:7.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a dose-response curve depicting propofol dose (milligrams per kilogram) versus sleep time (minutes) in Long Sleep (LS; open triangle) and Short Sleep (SS; solid triangle) mouse lines. Sleep time is defined as the duration of loss of righting reflex. Each point represents the mean sleep time ± SEM for n = 6-10. For every dose tested, the LS and SS lines are differentially sensitive (P < 0.01).

Fig. 2 is a bar graph depicting sleep times (minutes) in LS (open bars) and SS (hatched bars) mice. Routes of administration were jugular cannula (JUG; left bar of each pair) or retroorbital sinus (ROS; right bar of each pair) injections. Each bar represents means sleep time ± SEM (n = 7-9). There was a small, statistically significant difference in Short Sleep (SS) sleep times between the two techniques (P < 0.02) but no difference in Long Sleep (LS) sleep times (P = 0.09). Fig. 3 is a bar graph depicting effects of propofol on muscimol-stimulated ³⁶C1^" uptake in Long Sleep (LS, open bars) and Short Sleep (SS, hatched bars) brain membranes. Bars express the mean ± SEM. Eight to 10 female LS or SS mice were used per group.

Figs. 4 (A) and (B) are graphs depicting duration of LORR (loss of righting reflex) and BLA (brain levels of propofol at awakening) in pigmented and albino LSXSS RJ strains. Pigmented strains are shown as black bars; albino RI strains are shown as white bars. Error bars indicate standard error of the mean. In Fig. 4 (B), the strain distribution pattern mean LORR for propofol for the pigmented RI strains is indicated by the filled ovals, and the means for the albino RI strains is indicated by the open ovals. The numbers next to the ovals indicate the RI strain(s) having that mean. RI strain 32 had a mean LORR of 4.4 minutes (SEM = 0.7) for females and 6.6 minutes (SEM = 1.1 ) for males, but it was not included in this analysis because at that time it was still segregating for the albino mutation. Fig. 5 depicts a genetic map of murine chromosome 7 showing LOD scores for positioning Lorpl using the LSXSS RIs. Markers include the albino mutation (c), the pink- eyed dilution mutation (p) and six D7Mit SSLPs. The dashed line indicates the recommended threshold for statistical significance. Data were combined for males and females.

Fig. 6 depicts a genetic map of murine chromosome 7 showing confirmation of Lorpl from F intercrosses between ILS and ISS mice. Markers are D7Mit SSLPs. Marker D7MU31 is within the Tyr gene near the site of albino mutation, c. The dashed line indicates the recommended threshold for statistical significance. Data were combined for males and females (N = 164).

Figs. 7 (A) and (B) are bar graphs depicting propofol LORRs of (ISS c/c x C57BL/6 c^2j/C) F]S and of ILS and ISS mice with tyrosine. ILS (black bars) and ISS (white bars) mice coinjected with tyrosine (indicated as pr + tyr), substrate of the tyrosinase enzyme encoded by the albino gene, also did not exhibit significant differences in LORR (p = 0.78, ANOVA two-tailed significance) from controls at a concentration of tyrosine (200 mg/kg) previously shown to differentially alter ethanol-induced LORRs in LS and SS. "n" indicates the number of mice (males and females) tested. Error bars indicate standard error of the mean.

Fig. 8 depicts a genetic map of murine chromosome 7 showing LOD scores for positioning Lorpl using the LSXSS RIs. Results are shown for propofol, isoflurane. enflurane. and ethanol. The left-hand panels show data for females; the right-hand panels show data for males.

Fig. 9 depicts a genetic map of murine chromosome 7 showing LOD scores for positioning Lorpl using LSXSS RIs. This experiment was performed using etomidate. Fig. 10 depicts a genetic map of murine chromosome 7 showing confirmation of

Lorpl from F₂ intercrosses between ILS and ISS mice. This experiment was performed using etomidate.

Fig. 11 is a schematic depiction of YAC YRT2, containing a 250 kb genomic insert containing the mouse tyrosinase and mGluR5 genes. Expanded depiction of vector arms are shown below. Markers and functional elements from the vector arms are shown as filled arrows (except the open circle, which indicates the centromere). Numbers 1-5 indicate the exons of the tyrosinase gene. Tel, telomeres; Amp, ampicillin resistance gene; Tk, thymidine kinase gene of herpes simplex virus; Cen, centromere (CEN4); associated with the Gal-1 promoter (GAL1); TRP1 and URA3, yeast markers.

Fig. 12 is a bar graph comparing sleep times of SS (non-transgenic; left bar of each pair) and transgenic mice containing YRT2 (right bar of each pair) when given propofol. N = number of inj ections .

Fig. 13 is a schematic showing the strategy for analyzing mouse DNA sequences present on YRT2.

Fig. 14 (A)-(G) depicts the nucleotide sequence and a conceptual amino acid translation of most of the mouse mGluR5 coding region (SEQ ID NOS:l and 2). Fig. 15 shows a portion of mouse mGluR5 nucleotide sequence obtained from the

Genbank database and its conceptual amino acid translation (SEQ ID NOS:3 and 4).

Fig. 16 (A)-(G) depicts the nucleotide and amino acid sequences of rat mGluR5 (SEQ ID NOS:5 and 6).

Fig. 17 (A)-(C) depicts the amino acid sequence of human mGluR5 (SEQ ID NO:7).

MODES FOR CARRYING OUT THE INVENTION We have discovered mouse polynucleotide sequences that are associated with a particular, significant, biological phenomenon, namely sensitivity to CNS depressants. In particular, the sensitivity referred to herein (which may also be considered as decreased resistance) is with respect to a particular class of CNS depressants defined by the differential reactivity of LS and SS mice to these CNS depressants. This class of CNS depressants includes, but is not limited to, ethanol, chloral hydrate, enflurane, etomidate, flurazepam, halogenated ethanols, isoflurane, ketamine, midazolam, paraldehyde, MK-801, urethane and propofol. This discovery makes possible useful screening assays for agents which may exhibit CNS depressant activity as well as agents which may modulate CNS depressant sensitivity. This discovery may also lead to finding corresponding human sequences which confer differential sensitivity to CNS depressants, including ethanol, which in turn could provide the basis for powerful diagnostics in the context of, for example, ethanol sensitivity or vulnerability to ethanol addiction as well as determination of presence of risk factors for anesthesia administration. Mouse polynucleotide sequences were identified based on association with a particular biological function, namely, resistance to CNS depressant activity. Briefly, the polynucleotide and polypeptide sequences that form the basis of the screening methods described herein were discovered and obtained by: (a) mapping the genetic locus associated with the phenomenon of differential CNS depressant response; (b) complementation of the SS (resistant) phenotype to an LS (sensitive) phenotype by a YAC denoted YRT2 containing a 250 kb mouse genomic insert containing a tightly linked locus to the observed differential response phenomenon, namely, the albino (tyr) locus encoding tyrosinase. Thus, sequences contained in this YAC are associated with differential CNS depressant response. A schematic of YRT2 is depicted in Fig. 11.

The mapping experiments were conducted with propofol, enflurane, isoflurane, ethanol, and etomidate. In all cases, the trait associated with the differential response (the Lorpl locus) was significantly linked to the murine tyrosinase (albino) locus on chromosome 7. Thus, the sequences associated this differential sensitivity likely encompass the entire class of CNS depressants described above.

Definitions

As used herein, a "YRT2 polynucleotide" is a mouse polynucleotide sequence that is contained in, or corresponds to, a polynucleotide sequence within the yeast artificial chromosome (YAC) vector denoted YRT2, which is described and discussed herein. A schematic depiction of YRT2 is provided in Fig. 11. As the mouse polynucleotide sequences reflect a genomic configuration (i.e., the insert was obtained from a mouse genomic library), and the identity of at least part of the YAC insert is known, as well as the insert's genomic location, it is clear to those skilled in the art that these sequences may be obtained from sources other than YRT2 itself. It is understood that the definition of "YRT2 polynucleotide" includes, but is not limited to, polynucleotides contained within the tyrosinase gene and/or the mGluR5 gene. A gene, as understood by those of skill in the art, contains coding as well as non-coding sequences (such as 5' and 3' flanking sequences and introns). Accordingly, any definitions pertaining to YRT2 polynucleotides also apply to tyrosinase and mGluR5 polynucleotides.

A "YRT polypeptide" is a polypeptide that is encoded by a YRT2 polynucleotide. It is understood that the definition of "YRT2 polypeptide" includes, but is not limited to, polypeptides encoded within the tyrosinase gene and/or the mGluR5 gene. Accordingly, any definitions pertaining to YRT2 polypeptides also apply to tyrosinase and mGluR5 polypeptides.

A sequence "corresponding" to a sequence in YRT2 means that, when compared (i.e., aligned), the sequences share at least about 80% sequence identity, preferably at least about 85% sequence identity, more preferably at least about 90% sequence identity, even more preferably at least about 95% sequence identity, even more preferably at least about 98% sequence identity, most preferably 100% sequence identity. As discussed below, the term "corresponding" is used to emphasize that the sequences used in the methods described in this invention need not literally have been obtained from YRT2, but need only correspond in terms of contiguous nucleic acid composition to the sequences of YRT2. It is also understood that a sequence corresponding to YRT2 also applies to any polypeptide sequences encoded in the mouse polynucleotide sequence of YRT2, and that, as noted above for polynucleotide sequence identity, need not be a perfect correspondence to the sequence of YRT2 and need not be obtained by expressing YRT2 sequences per se.

As used herein, "expression" encompasses any level leading to, involving, and or resulting from production of a protein product. Accordingly, expression includes any aspect of transcription (including the modulation or effect of control sequences such as enhancers or promoters), translation, processing, sorting, post-translational modification(s), folding, conformation, assembly, subcellular and/or extracellular localization and/or position, binding, and/or effector function(s) (such as those involved in a signal transduction, or second messenger, pathway)_^.

A characteristic which is associated with "modulation" of expression is a characteristic which is associated with an alteration, increase or decrease, in expression. A "control region" of a gene is any sequence, of any length, which affects gene expression, most usually transcription. Examples of control regions include, but are not limited to, promoters and enhancers.

An "mGluR polynucleotide" refers to a polynucleotide contained within (or in) an mGluR gene. Examples of mGluR genes have been discussed and are known in the art. The mGluR polynucleotide may be of any origin, preferably eukaryotic, more preferably mammalian, such as mouse, human, or rat. However, it is understood that, due to sequence homology, an mGluR polynucleotide may also be obtained from other cell types, such as C. elegans, Drosophila, and yeast. For example, GenBank provides a homo log of mGluR as derived from C. elegans.

As used herein, "mGluR5 polynucleotide " refers to a polynucleotide contained within (or in) an mGluR5 gene. A "mouse mGluR5 polynucleotide" refers to a polynucleotide contained within (or in) a mouse mGluR5 gene. Similarly, a "mammalian mGluR5 polynucleotide" or "human mGluR5 polynucleotide" refers to a mammalian or human polynucleotide contained within or in a mammalian or human mGluR5 gene, respectively. A sequence of part of the mouse mGluR5 gene is depicted within SEQ ID NO: 1. A "fragment" or "region" of mGluR5 gene is a portion of the mGluR5 gene, and as such may contain coding and/or non-coding sequences. For example, SEQ ID NO: 1 contains a fragment of the mGluR5 in depicting the coding sequence. Preferably, a fragment of mGluR5 comprises at least 10 contiguous nucleotides, more preferably at least 15, more preferably at least 25, more preferably at least 30, more preferably at least 50, more preferably at least 100, more preferably at least 150, more preferably at least 200, more preferably at least 250, more preferably at least 300 contiguous nucleotides.

"mGluR5 " refers to a protein (polypeptide) product encoded in a mGluR5 gene. As noted for mGluR5 polypeptides above, a type (indicating genetic origin) of mGluR5 is specified, such as mouse, human, or mammalian. SEQ ID NO:2 depicts a conceptual translation of an open reading frame of mouse mGluR5. A "fragment" or "region" of mGluR5 (i.e., full-length) is a portion of the mGluR5 gene product. It is understood that mGluR5 may exist in more than one form, due to, for example, alternative splicing.

"mGluR5 function" or "mGluR5 activity" refers to an activity or characteristic associated with expression of mGluR5 . These functions include, but are not limited to, (a) transcription; (b) translation, including post-translational processing; (c) regulation by other polypeptides; (d) binding ligand; (e) signal transduction pathway (i.e., second messenger system) activity. For mGluR5, these signal transduction pathway activities include, but are not limited to, PI hydrolysis and mobilization of intracellular calcium.

As used herein, a characteristic which is associated with a "modulation" of mGluR5 function or activity is a characteristic which is associated with an alteration, increase or decrease, in mGluR5 function or activity. As used herein, "modulation of mGluR5 activity" means any change in any measurable parameter along the functional pathway of mGluR5. The "functional pathway" of mGluR5 includes transcription, translation, processing (including pre-and post-translational processing), positioning and/or conformation of receptor (either in solution or within a membrane context), binding to receptor, activities triggered by binding to the receptor (i.e., signal transduction pathway), and/or modulation of other neual receptor activities. "Suitable reaction conditions" refer to those conditions which allow a characteristic to be measured to occur. For example, if the characteristic is binding, then suitable reaction conditions are those which allow this binding to occur. If the characteristic is a signal transduction activity, then suitable reaction conditions are those which allow this activity to occur. Depending on which characteristic will be measured, the reaction conditions will vary. Determination of suitable reaction conditions is well within the skill of those in the art.

A sequence, whether polynucleotide or polypeptide, "depicted in" a SEQ ID NO, means that the sequence is present as an identical contiguous sequence in the sequence of the SEQ ID NO. Conversely, a contiguous sequence that is "not depicted in" a SEQ ID NO means that the contiguous sequence is not present as an identical contiguous sequence in the sequence of the SEQ ID NO. The term "contiguous" sequence and referring to, for example, an amino acid sequence of a specified length, are interchangeable in this context. As used herein, a "polynucleotide" is a polymeric form of nucleotides of any length, which contain deoxyribonucleotides, ribonucleotides, and/or their analogs. The terms "polynucleotide" and "nucleotide" as used herein are used interchangeably.

Polynucleotides may have any three-dimensional structure, and may perform any function, known or unknown. The term "polynucleotide" includes double- , single-stranded, and triple-helical molecules. Unless otherwise specified or required, any embodiment of the invention described herein that is a polynucleotide encompasses both the double-stranded form and each of two complementary single-stranded forms known or predicted to make up the double stranded form. Not all linkages in a polynucleotide need be identical.

The following are non-limiting examples of polynucleotides: a gene or gene fragment, exons, introns, mRNA, tRNA, rRNA, ribozymes, cDNA, recombinant polynucleotides, branched polynucleotides, plasmids, vectors, isolated DNA of any sequence, isolated RNA of any sequence, nucleic acid probes, primers, and adaptors. A polynucleotide may comprise modified nucleotides, such as methylated nucleotides and nucleotide analogs. The use of uracil as a substitute for thymine in a deoxyribonucleic acid is also considered an analogous form of pyrimidine.

In the context of polynucleotides, a "linear sequence" or a "sequence" is an order of nucleotides in a polynucleotide in a 5' to 3' direction in which residues that neighbor each other in' the sequence are contiguous in the primary structure of the polynucleotide. A

"partial sequence" is a linear sequence a portion of a polynucleotide, wherein the polynucleotide is known to comprise additional residues in one or both directions.

If present, modification to the nucleotide structure may be imparted before or after assembly of the polymer. The sequence of nucleotides may be interrupted by non- nucleotide components. A polynucleotide may be further modified after polymerization, such as by conjugation with a labeling component. Other types of modifications included in this definition are, for example, "caps", substitution of one or more of the naturally occurring nucleotides with an analog, internucleotide modifications such as, for example, those with uncharged linkages (e.g., methyl phosphonates, phosphotriesters, phosphoamidates, cabamates, etc.) and with charged linkages (e.g., phosphorothioates, phosphorodithioates, etc.), those containing pendant moieties, such as, for example, proteins (e.g., nucleases, toxins, antibodies, signal peptides, poly-L-lysine, etc.), those with intercalators (e.g., acridine, psoralen, etc.), those containing chelators (e.g., metals, radioactive metals, boron, oxidative metals, etc.), those containing alkylators, those with modified linkages (e.g., α-anomeric nucleic acids, etc.), as well as unmodified forms of the polynucleotide(s).

Further, any of the hydroxyl groups ordinarily present in the sugars may be replaced by phosphonate groups, phosphate groups, protected by standard protecting groups, or activated to prepare additional linkages to additional nucleotides, or may be conjugated to solid supports. The 5' and 3' terminal OH groups can be phosphorylated or substituted with amines or organic capping group moieties of from 1 to 20 carbon atoms. Other hydroxyls may also be derivatized to standard protecting groups.

Polynucleotides can also contain analogous forms of ribose or deoxyribose sugars that are generally known in the art, including, but not limited to, 2'-0-methyl-, 2'-0-allyl, 2'-fluoro- or 2'-azido-ribose, carbocyclic sugar analogs, α-anomeric sugars, epimeric sugars such as arabinose, xyloses or lyxoses, pyranose sugars, furanose sugars, sedoheptuloses, acyclic analogs and abasic nucleoside analogs such as methyl riboside. Although conventional sugars and bases will be used in applying the method of the invention, substitution of analogous forms of sugars, purines and pyrimidines can be advantageous in designing a final product, as can alternative backbone structures like a polyamide backbone. A polynucleotide or polynucleotide region has a certain percentage (for example,

75%, 80%, 85%, 90%, 95%, 98%, or 99%) of "sequence identity" to another sequence means that, when aligned, that percentage of bases are the same in comparing the two sequences. As is discussed further herein, "sequence identity" can be indicated by one of several measurable parameters, such as sequence alignment techniques (most typically performed with the use of standard alignment programs) and hybridization techniques, both of which are discussed herein.

"Hybridization" refers to a reaction in which one or more polynucleotides react to form a complex that is stabilized via hydrogen bonding between the bases of the nucleotide residues. The hydrogen bonding may occur by Watson-Crick base pairing, Hoogstein binding, or in any other sequence-specific manner. The complex may comprise two strands forming a duplex structure, three or more strands forming a multi-stranded complex, a single self-hybridizing strand, or any combination of these. A hybridization reaction may constitute a step in a more extensive process, such as the initiation of a PCR, or the enzymatic cleavage of a polynucleotide by a ribozyme. When hybridization occurs in an antiparallel configuration between two single-stranded polynucleotides, those polynucleotides are described as "complementary". A double-stranded polynucleotide can be "compLementary" to another polynucleotide if hybridization can occur between one of the strands of the first polynucleotide and the second. Complementarity (the degree that one polynucleotide is complementary with another) is quantifiable in terms of the proportion of bases in opposing strands that are expected to form hydrogen bonding with each other, according to generally accepted base-pairing rules.

A "primer" is a short polynucleotide, generally with a free 3' -OH group, that binds to a target potentially present in a sample of interest by hybridizing with the target, and thereafter promoting polymerization of a polynucleotide complementary to the target. An "adaptor" is a short, partially-duplexed polynucleotide that has a blunt, double- stranded end and a protruding, single-stranded end. It can be ligated, through its double- stranded end, to the double-stranded end of another polynucleotide. This provides known sequences at the ends of thus modified polynucleotides. Often adaptors contain specific sequences for primer binding and/or restriction endonuclease digestion.

A "probe" when used in the context of polynucleotide manipulation refers to a polynucleotide which is provided as a reagent to detect a target potentially present in a sample of interest by hybridizing with the target. Usually, a probe will comprise a label or a means by which a label can be attached, either before or subsequent to the hybridization reaction. Suitable labels include, but are not limited to radioisotopes, fluorochromes, chemiluminescent compounds, dyes, and enzymes.

"Transformation" or "transfection" refers to the insertion of an exogenous polynucleotide into a host cell, irrespective of the method used for the insertion, for example, lipofection, transduction, infection or electroporation. The exogenous polynucleotide may be maintained as a non-integrated vector, for example, a plasmid, or alternatively, may be integrated into the host cell genome.

A polynucleotide is said to "encode" a polypeptide if, in its native state or when manipulated by methods well known to those skilled in the art, it can be transcribed and/or translated to produce the polypeptide or a fragment thereof. For purposes of this invention, and to avoid cumbersome referrals to complementary strands, the anti-sense (or complementary) strand of such a polynucleotide is also said to encode the sequence; that is, a polynucleotide sequence that "encodes" a polypeptide includes both the conventional coding strand and the complementary sequence (or strand).

The terms "polypeptide", "oligopeptide", "peptide" and "protein^" are used interchangeably herein to refer to polymers of mino acids of any length. The polymer may be linear or branched, it may comprise modified amino acids, it may be interrupted by non-amino acids, and it may be assembled into a complex of more than one polypeptide chain. The terms also encompass an amino acid polymer that has been modified naturally or by intervention; for example, disulfide bond formation, glycosylation, lipidation, acetylation, phosphorylation, or any other manipulation or modification, such as conjugation with a labeling component. Also included within the definition are, for example, polypeptides containing one or more analogs of an amino acid (including, for example, unnatural amino acids, etc.), as well as other modifications known in the art.

In the context of polypeptides, a "linear sequence" or a "sequence" is an order of amino acids in a polypeptide in an N-terminal to C-terminal direction in which residues that neighbor each other in the sequence are contiguous in the primary structure of the polypeptide. A "partial sequence" is a linear sequence of a portion of a polypeptide, wherein the polypeptide is known to comprise additional residues in one or both directions. A polypeptide "fragment" (also called a "region") is a polypeptide comprising an amino acid sequence that has at least 5 contiguous amino acids of a sequence, more preferably at least 10 contiguous amino acids, more preferably at least about 15 contiguous amino acids, even more preferably at least about 25 contiguous amino acids, even more preferably at least about 30 contiguous amino acids, even more preferably at least about 40 contiguous amino acids, or even larger. A polypeptide or polypeptide region (or fragment) has a certain percentage of

"sequence identity" (for example, 75%, 80%, 85%, 90%, 95%, 98%, 99%) to another sequence means that, when aligned, that percentage of amino acids are the same in comparing the two sequences. As discussed herein, those skilled in the art generally use commercially available alignment programs to determine degree of sequence identity. A "fusion polypeptide" is a polypeptide comprising regions in a different position than occurs in nature. The regions may normally exist in separate proteins and are brought together in the fusion polypeptide, or they may normally exist in the same protein but are placed in a new arrangement in the fusion polypeptide.

A "functionally preserved" variant of a YRT2 polynucleotide or YRT2 polypeptide is a sequence which retains at least one aspect of YRT2 function. Functionally preserved variants can be due to differences in linear sequence, arising from, for example, single base mutation(s), addition(s), deletion(s), and/or modifϊcation(s) of the bases. The difference can also arise from changes in the sugar(s) and/or linkage(s) between the bases. Regarding polypeptides, functionally preserved variants may arise, for example, by conservative and/or non-conservative amino acid substitutions, amino acid analogs, and deletions. The function that is preserved depends upon the relevant function being considered. For example, a YRT2 polynucleotide is considered for its ability to encode a YRT2 polypeptide (or fragment thereof), then the ability of a variant sequence to encode the same polypeptide is the relevant function. If a YRT2 polypeptide is considered for its ability to bind to a particular entity (such as an antibody or ligand), then the ability of a variant sequence to encode a polypeptide with equivalent binding characteristics that is relevant. "Recombinant," as applied to a polynucleotide or gene, means that the polynucleotide is the product of various combinations of cloning, restriction and/or ligation steps, and other procedures that result in a construct that is distinct from a polynucleotide found in nature. A "vector" is a self-replicating nucleic acid molecule that transfers an inserted nucleic acid molecule into and/or between host cells. The term includes vectors that function primarily for insertion of a nucleic acid molecule into a cell, replication of vectors that function primarily for the replication of nucleic acid, and expression vectors that function for transcription and/or translation of the DNA or RNA. Also included are vectors that provide more than one of the above functions.

"Expression vectors" are defined as polynucleotides which, when introduced into an appropriate host cell, can be transcribed and translated into a polypeptide(s). An expression vector also comprises control elements operatively linked to the encoding region to enable and/or facilitate expression of the polypeptide in the target cell. An "expression system" usually connotes a suitable host cell comprised of an expression vector that can function to yield a desired expression product.

A "host cell" includes an individual cell or cell culture which can be or has been a recipient for vector(s) or for incorporation of nucleic acid molecules and/or proteins. Host cells include progeny of a single host cell, and the progeny may not necessarily be completely identical (in morphology or in genomic of total DNA complement) to the original parent cell due to natural, accidental, or deliberate mutation. A host cell includes cells transfected in vivo with a polynucleotide(s) of this invention.

A "cell line" or "cell culture" denotes eukaryotic cells, derived from higher, multicellular organisms, grown or maintained in vitro. It is understood that the descendants of a cell may not be completely identical (either morphologically, genotypically, or phenotypically) to the parent cell. Cells described as "uncultured" are obtained directly from a living organism, and are generally maintained for a limited amount of time away from the organism (i.e., not long enough or under conditions for the cells to undergo substantial replication). "Heterologous" means derived from (i.e., obtained from) a genotypically distinct entity from the entity to which it is being compared. For example, a polynucleotide may be placed by genetic engineering techniques into a plasmid or vector derived from a different source, thus becoming a heterologous polynucleotide. A promoter which is linked to a coding sequence with which it is not naturally linked is a heterologous promoter.

An "isolated" or "purified" polynucleotide, polypeptide, antibody or cell is one that is substantially free of the materials with which it is associated in nature. By substantially free is meant at least 50%, preferably at least 70%, more preferably at least 80%, and even more preferably at least 90% free of the materials with which it is associated in nature. As used herein, an "isolated" polynucleotide or polypeptide also refers to recombinant polynucleotides or polypeptides, which, by virtue of origin or manipulation: (1) are not associated with all or a portion of a polynucleotide or polypeptide with which it is associated in nature, (2) are linked to a polynucleotide or polypeptide other than that to which it is linked in nature, or (3) does not occur in nature, or (4) in the case of polypeptides arise from expression of recombinant polynucleotides. Thus, for example, an isolated substance may be prepared by using a purification technique to enrich it from a source mixture. Enrichment can be measured on an absolute basis, such as weight per volume of solution, or it can be measured in relation to a second, potentially interfering substance present in the source mixture. Increasing enrichments of the embodiments of this invention are increasingly more preferred. Thus, for example, a 2-fold enrichment is preferred, 10-fold enrichment is more preferred, 100-fold enrichment is more preferred, 1000-fold enrichment is even more preferred. A substance can also be provided in an isolated state by a process of artificial assembly, such as by chemical synthesis or recombinant expression.

A "stable duplex" of polynucleotides,_or a "stable complex" formed between any two or more components in a biochemical reaction, refers to a duplex or complex that is sufficiently long-lasting to persist between formation of the duplex or complex and subsequent detection, including any optional washing steps or other manipulation that may take place in the interim.

A substance is said to be "selective" or "specific" if it reacts or associates more frequently, more rapidly, with greater duration and/or with greater affinity with a particular cell or substance than it does with alternative cells or substances. An antibody "specifically binds" to a target if it binds with greater affinity, avidity, more readily, and/or with greater duration than it binds to other substances. As used herein, the term "agent" means a biological or chemical compound such as a simple or complex organic or inorganic molecule, a peptide, a protein or an oligonucleotide. A vast array of compounds can be synthesized, for example oligomers, such as oligopeptides and oligonucleotides, and synthetic organic compounds based on various core structures, and these are also included in the term "agent". In addition, various natural sources can provide compounds for screening, such as plant or animal extracts, and the like. Compounds can be tested singly or in combination with one another.

A "polymerase chain reaction" ("PCR") is a reaction in which replicate copies are made of a target polynucleotide using one or more primers, and a catalyst of polymerization, such as a reverse transcriptase or a DNA polymerase, and particularly a thermally stable polymerase enzyme. Methods for PCR are taught in U.S. Patent Nos. 4,683,195 (Mullis) and 4,683,202 (Mullis et al.). All processes of producing replicate copies of the same polynucleotide, such as PCR or gene cloning, are collectively referred to herein as "replication." An "antibody" (interchangeably used in plural form) is an immunoglobulin molecule capable of specific binding to a target, such as a polypeptide, through at least one antigen recognition site, located in the variable region of the immunoglobulin molecule. An antibody can be from any source of animal capable of producing them, for example, mouse, rat, rabbit, or human antibodies. As used herein, the term encompasses not only intact antibodies, but also fragments thereof (such as Fab, Fab', F(ab')₂, Fv, single chain

(ScFv)), mutants thereof, fusion proteins, humanized antibodies, and any other modified configuration of the immunoglobulin molecule that comprises an antigen recognition site of the required specificity. The term "antibody" includes polyclonal antibodies and monoclonal antibodies. "Immunological recognition" or "immunological reactivity" refers to the specific binding of a target through at least one antigen recognition site in an immunoglobulin or a related molecule, such as a B cell receptor or a T cell receptor.

The term "antigen" refers to the target molecule that is specifically bound by an antibody through its antigen recognition site. The antigen may, but need not be chemically related to the immunogen that stimulated production of the antibody. The antigen may be polyvalent, or it may be a monovalent hapten. Examples of kinds of antigens that can be recognized by antibodies include polypeptides, polynucleotides, other antibody molecules, oligosaccharides, complex lipids, drugs, and chemicals.

An "immunogen" is an antigen capable of stimulating production of an antibody when injected into a suitable host, usually a mammal. Compounds may be rendered immunogenic by many techniques known in the art, including crosslinking or conjugating with a carrier to increase valency, mixing with a mitogen to increase the immune response, and combining with an adjuvant to enhance presentation.

General Techniques The practice of the present invention will employ, unless otherwise indicated, conventional techniques of molecular biology (including recombinant techniques), microbiology, cell biology, biochemistry and immunology, which are within the skill of the art. Such techniques are explained fully in the literature, such as: "Molecular Cloning: A Laboratory Manual", second edition (Sambrook et al., 1989); "Oligonucleotide Synthesis" (M. J. Gait, ed., 1984); "Animal Cell Culture" (R.I. Freshney, ed., 1987); "Methods in

Enzymology" (Academic Press, Inc.); "Handbook of Experimental Immunology" (D.M. Wei & CC. Blackwell, eds.); "Gene Transfer Vectors for Mammalian Cells" (J.M. Miller & M.P. Calos, eds., 1987); "Current Protocols in Molecular Biology" (F.M. Ausubel et al., eds., 1987); "PCR: The Polymerase Chain Reaction", (Mullis et al., eds., 1994); "Current Protocols in Immunology" (J.E. Coligan et al., eds., 1991); Manipulating the Mouse

Embryo, second edition (Hogan et al., 1994); "Modern Biological Analysis of an Organism" (D.C. Shakes, eds., 1995).

Screening methods The present invention encompasses a variety of screening methods using the polynucleotide and/or polypeptide sequences described herein. These methods may be used as a basis for classifying agents in any of a number of ways, including, but not limited to, (a) agents which may exert CNS depressant activity, including candidate anesthetics; (b) agents that may be included in the class of agents in response to which LS and SS mice display differential sensitivity; (c) agents that may be included in the class of agents in response to which there is no differential sensitivity between LS and SS mice. The agents identified and classified under (b) and/or (c) may represent agents which act under two different kinds of mechanisms. Screening methods of this invention may also be used to identify agents which may modulate CNS depressant activity. Such an agent may be useful, for example, in administering a CNS depressant such as an anesthetic to certain at- risk or overly resistant individuals. Such an agent may also find use in administration to individuals who are overly sensitive to ethanol consumption or who are at risk of developing an addiction to ethanol.

These methods may be practiced in a variety of embodiments. The methods described herein encompass in vitro, cell-based, and in vivo screening assays. In the in vitro embodiments, an agent is tested for its ability to modulate function in a system which does not use intact cells. In the cell-based embodiments, living cells containing sequences described herein are used for testing agents. In the in vivo embodiments, transgenic mice harboring sequences described herein are used for testing agents.

Some of these screening embodiments employ mouse polynucleotide or polypeptide sequences contained in (or encoded in) YAC YRT2, or sequences corresponding to those sequences contained in (or encoded in) YAC YRT2. It is not necessary to know the identity of the sequence(s) (i.e., the individual contiguous nucleotide and/or amino acid identities) to practice these methods. For example, the sequence may be contained in a fragment (such as a restriction fragment or a fragment obtained by PCR) of YRT2, without knowledge of the nucleotide sequence identity of the fragment. Alternatively, a particular known sequence of YRT2 (or known sequence corresponding to a sequence of YRT2) may be used. It is not necessary to obtain sequences for these methods from YRT2 per se, as long as the sequence(s) correspond to those contained in (or encoded in) YRT2.

YRT2 is a YAC containing a 250 kb mouse genomic insert is depicted in Fig. 11 and is described by Schedl et al. (1993) Nature 362:258-261. YRT2 was obtained from a YAC library of C3H mouse DNA. Robertson (1987) "Tetracarcinomas and Embryonic

Stem Cells" (Robertson, ed.) at 71-112. YRT2 contains an 80kb polynucleotide sequence corresponding to the tyrosinase gene (Fig. 11). We have discovered that the remaining 170 kb contains the gene encoding mGluR5, a metabotropic glutamate receptor (discussed below). There may be other coding and/or control sequences in YRT2. Accordingly, another way of describing the sequences of YRT2, any portion of which may be used in the methods of this invention, are those mouse genomic sequences which encompass the region corresponding to the entire tyrosinase gene and another approximately 170 kb upstream of the tyrosinase gene.

How generally to prepare any of these sequences or relevant fragments is discussed in a later section addressing polynucleotides and polypeptides of the invention. It is understood that the description of preparation of sequences applies to sequences to be used for the screening methods described herein. Because the genomic location of the mouse sequences of YRT2 are known, and sequences contained within YRT2 are known, one skilled in the art could obtain sequences corresponding to sequences contained within YRT2 from sources other than YRT2 by using, for example, PCR methods applied to a suitable source of mouse DNA (i.e., a source of mouse DNA that would contain the desired sequences), such as commercially available libraries, genomic preparations, cDNA preparations, and DNA obtained by excised gel fragments. Alternatively, because we have shown that the Lorpl locus is tightly linked to the tyrosinase gene, these sequences could be used to obtain those and surrounding sequences from a murine genomic (or cDNA) library. Accordingly, mGluR5 sequences (discussed below) and/or tyrosinase sequences may also be used to obtain the desired sequences for these screening methods.

It is also understood that the sequences used in these screening methods can also include regulatory (non-coding) sequences, such as enhancers and/or promoters. When these sequences are used, reporter systems indicating regulatory region function may be employed. Such systems are well-known in the art, and include, but are not limited to, luciferase; aequorian (i.e., green fluorescent protein from Aequorea victoria); β- galactosidase; chloramphenicol acetyl transferase; immunologically detectable protein "tags" such as human growth hormone; and the like. See, for example, Current Protocols in Molecular Biology (F.M. Ausubel et al., eds., 1987) and periodic updates. Any assay which detects a product of the reporter gene, either by directly detecting the protein encoded by the reporter gene or by detecting an enzymatic product of a reporter gene- encoded enzyme, is suitable for use in the present invention. Assays include colorimetric, fluorimetric, or luminescent assays or even, in the case of protein tags, radioimmunoassays or other immunological assays. Many of these assays are commercially available. As noted in the definition of "agent" provided above, the agent may be any compound, complex or substance. Generally, the choice of agents to be screened is governed by several parameters, such as the particular polynucleotide or polypeptide target, its perceived function, its three-dimensional structure (if known or surmised), and other aspects of rational drug design. Techniques of combinatorial chemistry can also be used to generate numerous permutations of candidates. Those of skill in the art can devise and/or obtain suitable agents for testing. An agent is generally identified by its ability to modulate expression of the polynucleotide. As discussed, above, modulation of expression of a polynucleotide may occur at any level that affects its function. An agent may modulate polynucleotide expression by preventing, reducing or increasing transcription. An example of such an agent is one that binds to the upstream controlling region, including a polynucleotide sequence or polypeptide. An agent may modulate expression by preventing, reducing, or increasing translation of its corresponding mRNA. An example of such an agent is one that binds to the mRNA, such as an anti-sense polynucleotide, or an agent which selectively degrades the mRNA, or an agent that selectively stabilizing the mRNA. An agent may modulate expression by binding to the expressed polypeptide. An example of such an agent is a polypeptide or a chelator. Examples of the effect of such binding agents may include the degradation of the polypeptide, increased half-life of the polypeptide, prevention of polypeptide interaction with a ligand, and the stabilization of the polypeptide with a ligand.

In some embodiments, sequences contained in an mGluR5 gene (including 5' and 3' flanking (non-coding) sequences and introns), which encodes mGluR5, a subclass of metabotropic glutamate receptors, are used. We have discovered evidence that mouse mGluR5 sequences may be involved in this differential response to CNS depressants. For example, a comparison in which LS and SS mice were treated with an agonist of Group I mGluR (which includes mGluR5), ACPD, resulted in a greater change in increased resistance in SS (resistant) mice when compared to LS mice (Example 5). In another experiment, transgenic mice harboring the YAC in an SS background exhibited significantly longer sleep times when treated with an Group I agonist than control (non- transgenic) mice receiving the same agonist (Example 5). These observations suggest that a pathway(s) involving mGluR5 function may play a role in CNS sensitivity (and/or resistance). However, because of the complexity of CNS depressant reaction, and multiple pathways, the inventors are not confining their theory of the sequences associated with the differential CNS depressant response to mGluR5 gene or gene product. Other sequences on the YAC YRT2 described herein may be associated with this phenomenon, and are included in the screening methods described herein.

Further, because we have observed that mGluR5 appears to play a role in CNS depressant sensitivity in mice, we believe that this receptor plays an analogous functional role on other mammalian species, including human. The high degree of homology among mouse, rat, and human mGluR5 further supports this belief. See SEQ ID NOS: 5 and 6, which depict polynucleotide encoding rat mGluR5 (96% overall homology according to a BLAST search comparison) and the amino acid sequence of rat mGluR5 (over 96% overall homology (sequence identity), according to a BLAST search comparison); see also SEQ ID NO: 7, which depicts human mGluR5 (over 95% overall homology (sequence identity), according to a BLAST search comparison). Accordingly, the screening methods herein employ mGluR5 sequences, such as mammalian mGluR5, including, but not limited to, mouse, rat, and human. It is also possible, if not likely, that other mGluRs play a part in CNS depressant response. Accordingly, the methods described herein also employ mGluR sequences other than mGluR5, particularly those receptors in class I (mGluRl and mGluR5 and alternatively spliced variants) and class II (mGluR2 and mGluR3 and alternatively spliced variants). The other mGluR sequences that may be used in these methods include, not only mammalian sequences, but also non-mammalian sequences which show significant (i.e., over 50%) sequence identity to mammalian mGluR sequences. Example^'s of sources of these other mGluR sequences include, but are not limited to, C. elegans

(nemotode) and Drosophila. These sequences are readily available to those skilled in the art, given their publication on public databases such as Genbank and routine methods for obtaining and/or synthesizing polynucleotide sequences.

For any of these mGluR sequences, non-coding as well as coding regions may be used. For example, upstream control regions, such as promoters and/or enhancers, could be obtained and tested. If a non-coding control region is not publicly available on a database such as Genbank, these sequences may be obtained by using routine techniques in the art, such as chromosome walking using publicly available sequences as probes. For example, a cDNA probe containing coding sequences for an mGluR, such as human mGluR5, could be used to probe a human genomic library (or a genomic or cDNA library of another organism, if homologous sequences are desired). Positive, overlapping clones are then analyzed by, for example, restriction analysis. If sequences are desired even further from the probe sequence, sequentially overlapping clones may be obtained using probes derived from previously identified positive clones, thus effecting walking.

It is also understood that the screening methods of this invention include structural, or rational, drug design, in which the amino acid sequence, three-dimensional atomic structure or other property (or properties) of YRT2 polynucleotide or polypeptide (or mGluR5 polynucleotide or polypeptide) provides a basis for designing an agent which is expected to bind to YRT2 polynucleotide or polypeptide (or mGluR5 polynucleotide or polypeptide). Generally, the design and/or choice of agents in this context is governed by several parameters, such as the perceived function of the YRT2 polynucleotide or polypeptide (or mGluR5 polynucleotide or polypeptide) target, its three-dimensional structure (if known or surmised), and other aspects of rational drug design. Techniques of combinatorial chemistry can also be used to generate numerous permutations of candidate agents.

The screening methods described above represent primary screens, designed, inter alia, to detect any agent that may exhibit CNS depressant activity, or modulate such activity. The skilled artisan will recognize that secondary tests will likely be necessary in order to evaluate an agent further. For example, because a characteristic associated with expression of a YRT2 polynucleotide is generally assessed, it may be desirable to further confirm that this characteristic is involved with CNS depressant activity. One way of accomplishing this would be to conduct the experiment using a known CNS depressant. If the response (i.e., the impact on expression of the YRT2 polynucleotide or mGluR5 polynucleotide) is similar or the same as that. response caused by the agent to be tested, it is reasonable to surmise that the characteristic observed is involved in CNS depressant activity. In vitro embodiments

In in vitro screening methods of this invention, an agent is screened in an in vitro system, which may include either of the following: (1) an assay for an agent which modulates the translation of a YRT2 (or mGluR5) mRNA or a YRT2 polynucleotide (or an mGluR polynucleotide, including mGluR5) encoding a polypeptide; (2) an assay for an agent that binds to a YRT2 (or mGluR5) polynucleotide(s) or polypeptides (or to a mammalian mGluR polypeptide, including mGluR5). Accordingly, the invention includes methods of identifying an agent which modulates a YRT2 polynucleotide encoding a YRT2 polypeptide, comprising combining at least one agent to be tested with a YRT2 polynucleotide which encodes a YRT2 polypeptide under suitable reaction conditions, and determining whether the at least one agent modulates this polynucleotide by analyzing at least one characteristic associated with translation of the YRT2 polynucleotide. The invention also includes methods of identifying an agent which binds to a YRT2 polynucleotide or polypeptide, comprising combining at least one agent with a YRT2 polynucleotide or polypeptide under suitable reaction conditions, and determining whether the at least one agent binds to the YRT2 polynucleotide or YRT2 polypeptide. Examples of these types of assays are provided below. These methods also pertain to using mGluR polypeptide(s) and/or polynucleotide(s), such as mammalian mGluR, such as mGluR5, which includes mouse mGluR5. For the discussion which follows, it is understood that the YRT2 sequences serve as example and that these techniques pertain also to mGluR sequences. For an assay that determines whether an agent modulates the translation of YRT2 mRNA or a polynucleotide encoding a YRT2 polypeptide, an in vitro transcription/translation system may be used. These systems are available commercially and provide an in vitro means to produce mRNA corresponding to a polynucleotide sequence of interest. After YRT2 mRNA is made, it can be translated in vitro and the translation products compared. Comparison of translation products between an in vitro expression system that does not contain any agent (negative control) with an in vitro expression system that does contain an agent indicates whether the agent is affecting translation. Comparison of translation products between control and YRT2 polynucleotides indicates whether the agent, if acting on this level, is selectively affecting translation of the YRT2 mRNA (as opposed to affecting translation in a general, non- selective or non-specific fashion).

In an example for an assay for an agent that binds to a YRT2 polypeptide, a YRT2 polynucleotide encoding a polypeptide is first recombinantly expressed in a prokaryotic or eukaryotic expression system as a native or as a fusion protein in which the YRT2 polypeptide is conjugated with a well-characterized epitope or protein as described under

"Preparation of polypeptides of this invention". Recombinant YRT2 polypeptide is then purified by, for instance, immunoprecipitation using anti-YRT2 polypeptide antibodies or anti-epitope antibodies or by binding to immobilized ligand of the conjugate. An affinity column made of YRT2 polypeptide or YRT2 polypeptide-fusion protein is then used to screen a mixture of compounds which have been appropriately labeled. Suitable labels include, but are not limited to fluorochromes, radioisotopes, enzymes and chemiluminescent compounds. The unbound and bound compounds can be separated by washes using various conditions (e.g. high salt, detergent ) that are routinely employed by those skilled in the art. Non-specific binding to the affinity column can be minimized by pre-clearing the compound mixture using an affinity column containing merely the conjugate or the epitope. Similar methods can be used for screening for an agent(s) that competes for binding to YRT2 polypeptides. In addition to affinity chromatography, there are other techniques such as measuring the change of melting temperature or the fluorescence anisotropy of a protein which will change upon binding another molecule. For example, a BIAcore assay using a sensor chip (supplied by Pharmacia Biosensor, Stitt et al. (1995) Cell 80: 661-670) that is covalently coupled to native YRT2 polypeptide, fragments thereof, or YRT2 polypeptide-fusion proteins, may be performed to determine the YRT2 polypeptide binding activity of different agents.

It is understood that anti-YRT2 polypeptide antibodies, including anti-mGluR5 antibodies, can be used to determine whether agents which interact with YRT2 polypeptides alter the structure and/or conformation of the YRT2 polypeptide. For example, a conformational change and/or structural alteration induced by contact with an agent may result in the YRT2 polypeptide becoming unrecognizable by the YRT2 polypeptide-specific antibodies. The loss of the ability of a monoclonal anti-YRT2 polypeptide antibody to immunoprecipitate YRT2 polypeptide after the polypeptide has been contacted by the agent would suggest that the agent had interfered, either directly or through a conformational change and/or a structural alteration, with the antibody recognition site on the YRT2 polypeptide. Other ways to assess this interaction are well known in the art. As such a change may alter YRT2 polypeptide function, agents screened for their effect on YRT2 polypeptide - anti-YRT2 polypeptide interactions would be useful for the refinement of those agents known to interact with YRT2 polypeptide to those that may alter YRT2 polypeptide polynucleotide(s) function. Methods for making antibodies are known in the art and need not be described in detail herein. Cell-based embodiments These embodiments employ cell systems containing YRT2 and/or mGluR polynucleotides and/or polypeptide(s) (which, as the definitions make clear, include sequences corresponding to YRT2 polynucleotides and/or polypeptides). In one embodiment, the method provides methods for identifying an agent which may exhibit CNS depressant activity, comprising the steps of (a) introducing a polynucleotide comprising a mouse associated with CNS depressant sensitivity into a suitable host cell, wherein the polynucleotide comprises a mouse polynucleotide sequence corresponding to a polynucleotide sequence contained in yeast artificial chromosome YRT2; (b) contacting host cell of step (a) with at least one agent to be tested; (c) analyze at least one characteristic associated with expression of the polynucleotide, wherein an agent is identified by its ability to modulate expression of the mouse YRT2 polynucleotide.

In another embodiment, the invention provides methods for classifying a CNS depressant comprising the steps of (a) introducing a polynucleotide associated with CNS depressant sensitivity into a suitable host cell, wherein the polynucleotide comprises a mouse polynucleotide sequence corresponding to a polynucleotide sequence contained in yeast artificial chromosome YRT2; (b) contacting the host cell with the CNS depressant to be classified; (c) analyzing at least one characteristic associated with expression of the polynucleotide, wherein a CNS depressant which modulates expression may fall within that class of CNS depressants which displays differential reactivity with respect to LS and SS mice.

These methods could also be used to identify an agent which may modulate CNS depressant activity. In another embodiment, the invention provides methods for identifying an agent which may modulate CNS depressant sensitivity in an individual, comprising (a) introducing a polynucleotide associated with CNS depressant sensitivity into a suitable host cell, wherein the polynucleotide comprises a mouse polynucleotide sequence corresponding to a polynucleotide sequence contained in yeast artificial chromosome YRT2, (b) contacting host cell of step (a) with at least one agent to be tested; (c) analyze at least one characteristic associated with expression of the polynucleotide, wherein an agent is identified by its ability to modulate expression of the mouse YRT2 polynucleotide. Preferably, these methods would compare the effect of an agent alone versus the agent in the presence of a CNS depressant (i.e., contacting the cell with the CNS depressant in addition to the agent). All of these methods preferably include a control sample which does not receive the agent(s). The characteristic(s) to be analyzed may be assessed in any number of ways, including, but not limited to, microscopic analysis, viability testing, ability to replicate, histological examination, the level of a particular RNA or polypeptide associated with the cells, the level of enzymatic activity expressed by the cells or cell lysates, and the ability of the cells to interact with other cells or compounds. Differences between treated and untreated cells indicate effects attributable to the agent(s). Optimally, the agent has a greater effect on experimental cells than on control cells.

To identify agents that specifically modulate YRT2 polynucleotide transcription, for example, the transcription regulatory regions of a gene contained in YRT2 could be linked to a reporter gene and the construct added to an appropriate host cell. As used herein, the term "reporter gene" means a gene that encodes a gene product that can be identified (i.e., a reporter protein). Reporter genes include, but are not limited to, alkaline phosphatase, chloramphenicol acetyltransferase, β-galactosidase, luciferase and green fluorescence protein (GFP). Identification methods for the products of reporter genes include, but are not limited to, enzymatic assays and fluorimetric assays. Reporter genes and assays to detect their products are well known in the art and are described, for example in Ausubel et al. (1987) and periodic updates. Reporter genes, reporter gene assays and reagent kits are also readily available from commercial sources. Cells transcribing YRT2 mRNA or polynucleotide could be used to identify agents that specifically modulate the half-life of YRT2 mRNA (or polynucleotide) and/or the translation of YRT2 mRNA. Such cells would also be used to assess the effect of an agent on the processing and/or post-translational modification of a YRT2 polypeptide. An agent could modulate the amount of YRT2 polypeptide in a cell by modifying the turn-over (i.e., increase or decrease the half-life) of the YRT2 polypeptide(s). The specificity of the agent with regard to the YRT2 mRNA and polypeptide would be determined by examining the YRT2 products in the absence of the agent and by examining the products of unrelated mRNAs and polypeptides. Methods to examine mRNA half-life, protein processing, and protein turn-over are well know to those skilled in the art. Cell-based screening methods could also be useful in the identification of agents that modulate YRT2 polypeptide function through the interaction with a YRT2 polypeptide directly. Such agents could block normal YRT2 polypeptide-ligand interactions, if any, or could enhance or stabilize such interactions. The effect of the agent could be determined using immunoprecipitation reactions. Anti-YRT2 polypeptide antibodies would be used to precipitate YRT2 polypeptide and any protein tightly associated with it. By comparing the polypeptides immunoprecipitated from treated cells and from untreated cells, an agent could be identified that would augment or inhibit YRT2 polypeptide-ligand interactions, if any. YRT2 polypeptide-ligand interactions could also be assessed using cross-linking reagents that convert a close, but noncovalent interaction between polypeptides into a covalent interaction. Techniques to examine protein-protein interactions are well known to those skilled in the art. As discussed above, it is understood that these screening methods also encompass using mGluR sequences, including mammalian mGluR5 from mouse, rat, or human, such as human mGluR5.

For methods using mGluR5 sequences, modulation of mGluR5 activity is measured. Accordingly, an agent may modulate mGluR5 function by affecting any of the following non-limiting examples: transcription; translation; post-translational modification; conformation, including conformation of intact receptor; placement in membrane; cellular localization; interaction with other mGluRs; interaction with ligand; interaction with other moieties; altering a function of a member of a signal transduction pathway.

Any of these levels of mGluR5 function may be measured using methods known in the art. Assays for measuring alterations in transcription, translation, and binding have been discussed above. As further example, modulation of mGluR5 activity may be ascertained by measuring the effects on intracellular calcium, inositol phosphate, and/or cyclic AMP (cAMP).

Intracellular calcium concentration can be measured using methods known in the art, such as fura-2. Briefly, recombinant cells expressing mGluR5 (or a functional fragment thereof) are loaded with fura-2 and suspended in buffer containing 0.5 mM CaCl₂. An agent(s) is added, and changes in fluorescence signal are measured. Agent(s) may be added over a range of concentrations.

Ion-exchange columns eluted with chloride provide a relatively rapid means of screening for inositol phosphate formation. Inositol phosphate may further be studied using HPLC. cAMP levels may be measured by heating a sample treated with agent in water at about 70°C for about 5-10 minutes. Cellular debris is removed by centrifugation after cycles of freezing and thawing. cAMP concentration is determined by RIA.

Suitable host cells for these methods include any host cell which is capable of accepting and expressing a YRT2 (or mGluR) polynucleotide. Examples of suitable host cells include eukaryotic cells, such as yeast cells (such as, for example P. pastoris, Saccharomyces cerevisiae, Candidatropicalis, Hansenula polymorpha, Schizosaccharomyces pombe and the like), insect cells, fungal cells, amphibian cells (such as Xenopus), nemotode cells (such as C. elegans) and mammalian cells. Mammalian cells are widely available and need not be discussed in detail herein. Exemplary cells for suitable for practicing these methods include COS cells, mouse L cells, Chinese hamster ovary (CHO) cells, human embryonic kidney (HEK) cells, African green monkey cells, all of mammalian origin; Xenopus laevis oocytes, of amphibian origin; Saccharomyces cerevisiae, Pichia pastoris which are yeast. Exemplary cells for expressing injected RNA transcripts include Xenopus laevis oocytes. Methods for injecting Xenopus oocytes are well-known in the art. Other, more particular, cell types, well-known to those skilled in the art, include HEK293; Ltk^" cells; CDS-7 cells; CHO cells; DG44 cells (dhfr CHO cells; e.g., Urlaub et al. (1986) Cell. Molec. Genet. 12:555); BHK cells, and cells of neuronal origin, such as HCN1A andHCN2 (derived from human CNS). Virtually all of these cell types, as well as other suitable cell types, such as neural cells, are either commercially available or are available through the ATCC.

For methods involving mGluR5 sequences, mammalian expression systems, including commercially available systems and other such systems known to those of skill in the art which express G-proteins (either endogenously or recombinantly), for expression of DNA encoding the human metabotropic glutamate receptor subtypes provided herein, are preferred. Xenopus oocytes are preferred for expression of in vitro mRNA transcripts of DNA encoding those human metabotropic receptor subtypes that are coupled to the PI hydrolysis/Ca⁺⁺ signalling pathways. An endogenous inositol triphosphate second messenger-mediated pathways in oocytes permits functional expression of human metabotropic receptors in these cells. Oocytes expressing recombinant human metabotropic receptors respond to agonist via the oocyte G-protein-coupled IP₃ generation pathway, which stimulates release of Ca^"1"*^" from internal stores, and reportedly activates a chloride channel that can be detected as a delayed oscillatory current by voltage-clamp recording. Methods for injecting Xenopus oocytes are well-known in the art.

Host cells for functional recombinant expression of human metabotropic receptors preferably express endogenous or recombinant guanine nucleotide-binding proteins (i.e., G-proteins). G-proteins are a highly conserved family of membrane-associated proteins composed of α, β and γ subunits. The α subunit, which binds GDP and GTP, differs in different G-proteins. The attached pair of β and γ subunits may or may not be unique; different α claims may be linked to an identical αγ pair or to different pairs. Linder and Gilman (1992) Sci. Am. 267:56-65. More than 30 different cDNAs encoding G protein α subunits have been cloned. See, for example, Simon et al. (1991) Science 252:802. Four different β polypeptide sequences are known. Simon et al. (1991). Three of five identified γcDNAs have been cloned. Hurley et al. (1984) Proc. Natl. Acad. Sci. U.S.A. 81 :6948; Gautam et al. (1989) Science 244:971; and Gautam et al.(1990) Proc. Natl. Acad. Sci. U.S.A. 87:7973. The sequences of a fourth γ cDNA (Kleuss et al. (1993) Science 259:832) and a fifth γ cDNA (Fisher and Aronson (1992) Mol. Cell. Bio. 12:1585) have been established, and additional γ subtypes may exist (Tamir et al. (1991) Biochemistry 30:3929. G-proteins switch between active and inactive states by guanine nucleotide exchange and GTP hydrolysis. Inactive G protein is stimulated by a ligand activated receptor to exchange GDP for GTP. In the active form, the α subunit, bound to GTP, dissociates from the βγ complex, and the subunits then interact specifically with cellular effector molecules to evoke a cellular response. Because different G-proteins can interact with different effector systems (e.g., phospholipase C, adenyl cyclase systems) and different receptors, it is useful to investigate different host cells for expression of different recombinant human metabotropic receptor subtypes. Alternatively, host cells can be transfected with G-protein subunit-encoding DNAs for heterologous expression of differing G proteins.

A practitioner of ordinary skill will be well acquainted with techniques for transfecting eukaryotic cells, including the preparation of a suitable vector, such as a viral vector; conveying the vector into the cell, such as by electroporation; and selecting cells that have been transformed, such as by using a reporter or drug sensitivity element. The effect of an agent on transcription from a YRT2 regulatory region in these constructs would be assessed through the activity of the reporter gene product. DNA may be stably incorporated into cells or may be transiently expressed using methods known in the art. Stably transfected mammalian cells may be prepared by transfecting cells with an expression vector having a selectable marker gene (such as, for example gene for thymidine kinase, dihydrofolate reductase, neomycin resistance, and the like), and growing the transfected cells under conditions selective for cells expressing the marker gene. To prepare transient transfectants, mammalian cells are transfected with a reporter gene (such as the E. coli β-galactosidase gene) to monitor transfection efficiency. Selectable marker genes are typically not included in the transient transfections because the transfectants are typically not grown under selective conditions, and are usually analyzed within a few days after transfection.

In vivo embodiments

The invention also includes methods for identifying agents based on transgenic, or in vivo, systems. For these methods, an agent is administered to a transgenic animal, such as a mouse, harboring, for example, mouse sequences corresponding to YRT2 as described above. The agent is assessed by analyzing a characteristic associated with CNS depressant activity, such as, for example, loss of righting reflex (LORR), or sleep times. Various agents may be assessed for their ability or inability to affect any of these characteristics. Various agents may also be assessed for their ability to alter the effect of a CNS depressant, thus indicating that this agent(s) may modulate CNS depressant activity. Accordingly, the invention includes methods of identifying an agent which may exhibit CNS depressant activity, comprising the steps of (a) adminstering an agent to a transgenic animal containing an introduced mouse YRT2 sequence; and (b) analyzing at least one characteristic associated with CNS depressant activity, wherein an agent is identified by its ability to modulate the characteristic. The invention also includes methods of classifying agents and methods of identifying an agent which may modulate CNS depressant activity using these steps. For any of these transgenic embodiments, characteristics which are associated with CNS depressant activity include, but are not limited to, sleep (unconsciousness) time, degree of loss of reflex or response to stimuli, and degree of loss of pain response. Alternatively, the transgenic embodiments may employ mGluR sequences as described above.

Preferably, these methods are performed by comparing the effect of the agent(s) on the transgenic animal described above with the effect on a SS (resistant) mouse. Candidate CNS depressant agents may also be thus classified by making this comparison with respect to whether they belong in the class of CNS depressants which display differential activity in LS versus SS mice.

In one embodiment, the transgenic animal (such as mouse) contains mGluR5 sequences. These mGluR5 sequences may be from a mammal, such as mouse, rat, primate or human. Alternatively, the transgenic animal contains other mGluR sequences, such as mGluRl, mGluR2, mGluR3, mGluR4, mGluRό, mGluR7 and mGluR8 (as well as any splice variants or non-mammalian mGluR homologs). Any of these various mGluR sequences may be from mammalian systems, such as mouse, rat, primate or human, or non- mammalian systems, such as homologous sequences from Drosophila and C. elegans.

Obtaining these sequences has been described above. A transgenic animal may be mammals, such as mice, rats, primate, cows, pigs, dogs and cats. Alternatively, a transgenic animal may be an invertebrate, such as Drosophila or C. elegans (nemotode). Methods of making transgenic animals, particularly mice, are known in the art. Briefly, polynucleotide sequence(s) are isolated using standard methods of the art. Purified polynucleotide (usually DNA) is injected or introduced into appropriate early cell types or lineages, such as oocytes. See, for example, Brinster et al.(1985) Proc. Natl. Acad. Sci. USA 82:4438-4442. Other means known in the art of introducing the polynucleotide are transfection and transduction. Alternatively, appropriate cells may be infected with viruses, such as retroviruses of adenoviruses, which are modifed to carry the polynucleotide sequences to be introduced.

Pluripotent stem cells derived from the inner cell mass of the embryo and stabilized in culture can be manipulated in culture to incorporate nucleotide sequences. A transgenic animal can be produced from such stem cells through implantation into a blastocyst that is implanted into a foster mother an allowed to come to term. In the case of mice, injected oocytes are transferred into pseudopregnant females. Animals suitable for transgenic experiments can be obtained from standard commercial sources such as Charles River (Wilmington, MA) and Harlan Sprague Dawley (Indianapolis, IN).

Methods for culturing embryonic stem (ES) cells and the subsequent production of transgenic animals by the introduction of DNA into ES cells using methods such as electroporation, calcium phosphate/DNA precipitation and direct injection are well known in the art, as are procedure for embryo manipulations. Microinjection procedures for fish, amphibian eggs and birds are detailed by Houdebine and Chourrout (1991) Experientia 47:897-905. See also U.S. Pat. 4,945,050.

Transfection and isolation of desired clones can be carried out using standard techniques. For example, random gene integration can be carried out by co-transfecting the nucleic acid with a gene encoding antibiotic resistance. Alternatively, the gene encoding antibiotic resistance is physically linked to a polynucleotide used in the screening methods described herein.

DNA molecules introduced into ES cells can also be integrated into the chromosome through homologous recombination. See, for example, Capecchi (1989) Science 244: 1288-1292. Methods for positive selection of the recombination event (such as neomycin resistance) and dual positive-negative selection (e.g., neomycin resistance and gancyclovir resistance) and the subsequent identification of desired clones by PCR are methods standard in the art. Capecchi (1989); Joyner et al. (1989) Notwre 338:153-156. Targeted ES cells are then injected into blastocysts, which are transferred into pseudopregnant females. Resulting chimeric animals are bred and offspring analyzed by

Southern blotting to identify individuals carrying the introduced polynucleotide sequences.

Transgenic mice are identified by preparing DΝA from, for example, tail biopsies and simultaneous hybridization with appropriate probes that indicate the presence of introduced DΝA. In certain circumstances, presence of introduced DΝA (polynucleotide) is indicated by a measurable phenotype, such as change in pigmentation. The transgenic animal (herein exemplified by mouse, due to its more common use) may or may not have more than one copy of the YRT2 sequence(s) or mGluR sequence(s). Depending on the nature of the experiment, it may also be desirable to generate different transgenic lines which have different copy numbers. Copy number can be determined by using methods standard in the art, such as Southern blot analysis or PCR.

The procedure for generating transgenic rats is similar to that of mice. See, for example, Hammer et al. (1990) Cell 63:1099-1112. Procedures for production of transgenic non-rodent mammals and other animals are also known in the art. See, for example, Houdebine and Chourrout; Pursel et al. (1989) Science 244:1281-1288; Simms et al. (1988) Bio/Technology 6:179-183.

If desired, the endogenous mGluR gene may be inactivated. This may be accomplished, for example, by using a recombinant gene engineered to contain an insertional mutation (such as neo). The recombinant gene is inserted into the genome of a recipient cells, tissue, or animal, and transcription of the endogenous mGluR is prevented, or decreased.

Polynucleotide and polypeptide sequences of the invention

The invention provides new polynucleotide and polypeptide sequences associated with differential CNS depressant response, namely, a class of CNS depressants defined by a differential response/sensitivity in LS versus SS mice. Examples of these CNS depressants are discussed above. In particular, the invention provides mouse mGluR5 polynucleotide and polypeptide sequences. These sequences have a variety of uses, including use in screening methods described above, as indicators of CNS depressant function, and use in obtaining corresponding human sequences which are associated with differential response to CNS depressants, which in turn may provide a useful drug target. The polynucleotide sequence of most of mGluR5 coding region is depicted in SEQ ID NO: 1. The polypeptide sequence of most of mGluR5 is depicted in SEQ ID NO:2.

Bacteria containing respective cloned DNA have been deposited with the American Type Culture Collection (ATCC), 12310 Parklawn Drive, Rockville, Maryland, U.S.A.

20852 on , 199_, under the provisions of the Budapest Treaty for the

International Recognition of the Deposit of Microorganisms for the Purposes of Patent Procedure. They were accorded Accession Numbers as follows:

Polynucleotides of the invention

The invention provides mGluR5 polynucleotides, which will be described below. The invention also provides vectors containing these polynucleotides, host cells containing these polynucleotides, and compositions comprising these polynucleotides. These polynucleotides are isolated and/or produced by chemical and/or recombinant methods, or a combination of these methods. Unless specifically stated otherwise, "polynucleotides" shall include all embodiments of the polynucleotides of this invention. It is also understood that, all polynucleotide embodiments are isolated polynucleotides. The cloning of mGluR5 polynucleotide sequences is described in Example 4. Examination of Genbank using a

BLAST search revealed that a portion of mouse mGluR5, represented by an exon, had previously been obtained (SEQ ID NO:3). However, the conceptual translation of this region does not correspond to the conceptual amino acid translation of SEQ ID NO:l, which is depicted in SEQ ID NO:2.

Accordingly, this invention provides an isolated polynucleotide that contains a sequence encoding a mouse mGluR5 polypeptide wherein the polypeptide is at least about 10 amino acids in length and is depicted in SEQ ID NO:2 but not depicted in SEQ ID NO:6

(rat mGluR5 amino acid sequence) or SEQ ID NO: 7 (human mGluR5 amino acid sequence). In other embodiments, the mouse mGluR5 encoded is at least about 20, at least about 25, at least about 50, at least about 75, at least about 100, at least about 125, at least about 200, at least about 250, at least about 300, at least about 350, at least about 400, at least about 500, at least about 700, at least about 750, at least about 1000 amino acids in length and depicted in SEQ ID NO:2 but not depicted in SEQ ID NO:6 or SEQ ID NO:7. The invention also includes an isolated polynucleotide comprising a polynucleotide encoding the polypeptide of SEQ ID NO:2.

In other embodiments, the invention includes an isolated polynucleotide comprising a polynucleotide of at least about 10 contiguous nucleotides of SEQ ID NO : 1 , wherein the about 10 contiguous nucleotides are not depicted in SEQ ID NO: 3 (the above-discussed mouse mGluR5 sequence on the Genbank database) or SEQ ID NO: 5 (rat mGluR5 polynucleotide sequence). Alternatively, the invention includes an isolated polynucleotide comprising a polynucleotide of at least about 10 contiguous nucleotides of nucleotide 1 to 2625 SEQ ID NO: 1 , wherein the 10 contiguous nucleotides are not depicted in SEQ ID

NO:5. The invention also includes an isolated polynucleotide comprising a polynucleotide of at least about 10 contiguous nucleotides ofnucleotide 2726 to 3591 of SEQ ID NO:l, wherein the 10 contiguous nucleotides are not depicted in SEQ ID NO:5. Alternatively, the isolated polynucleotide comprises a polynucleotide of at least about 25, at least about 50, at least about 75, at least about 100, at least about 150, at least about 200, at least about 250, at least about 300, at least about 500, at least about 750, at least about 1000 contiguous nucleotides of SEQ ID NO:l, wherein the contiguous nucleotides are not depicted in SEQ ID NO:5. In another embodiment, the invention includes a polynucleotide comprising the sequence of SEQ ID NO: 1. The shorter embodiments are useful, for example, as probes as well as providing a template for production of mGluR5 polypeptide(s) and/or functional fragments. The invention includes modifications to the mGluR5 polynucleotides described above such as deletions, substitutions, additions, or changes in the nature of any nucleic acid moieties. A "modification" is any difference in nucleotide sequence as compared to a polynucleotide shown herein to encode an mGluR5 polypeptide, and/or any difference in terms of the nucleic acid moieties of the polynucleotide(s). Such changes can be useful to facilitate cloning and modifying expression of mGluR5 polynucleotides. Such changes also can be useful for conferring desirable properties to the polynucleotide(s), such as stability. The definition of polynucleotide provided herein gives examples of these modifications. Hence, the invention also includes functionally-preserved variants of the nucleic acid sequences disclosed herein, which include nucleic acid substitutions, additions, and/or deletions.

The invention also encompasses mGluR5 polynucleotides including full-length (unprocessed), processed, coding, non-coding (including flanking region) or portions thereof, provided that these polynucleotides contain a region encoding at least a portion of mGluR5. Also embodied are the mRNA and cDNA sequences and fragments thereof that include a portion mGluR5 encoding segment.

The invention also encompasses polynucleotides encoding for functionally equivalent variants and derivatives of full-length mGluR5 and functionally equivalent fragments thereof which may enhance, decrease or not significantly affect properties of the polypeptides encoded thereby. For instance, changes in a DNA sequence that do not change the encoded amino acid sequence, as well as those that result in conservative substitutions of amino acid residues, non-deleterious non-conservative substitutions, one or a few amino acid deletions or additions, and substitution of amino acid residues by amino acid analogs are those which will not significantly affect properties of the encoded polypeptide. Nucleotide substitutions that do not alter the amino acid residues encoded can be useful for optimizing gene expression in different systems. Suitable substitutions are known to those of skill in the art and are made, for instance, to reflect preferred codon usage in the particular expression systems. In another example, alternatively spliced polynucleotides can give rise to a functionally equivalent fragment or variant of mGluR5. Alternatively processed polynucleotide sequence variants are defined as polynucleotide sequences corresponding to mRNAs that differ in sequence for one another but are derived from the same genomic region, for example, mRNAs that result from: 1 ) the use of alternative promoters; 2) the use of alternative polyadenylation sites; and/or 3) the use of alternative splice sites.

The mGluR5 polynucleotides of the invention also include polynucleotides encoding other mGluR5 fragments. The polynucleotides encoding mGluR5 fragments are useful, for example, as probes, therapeutic agents, a polypeptide processing signal, and as a template for encoding various functional domains of mGluR5. Accordingly, the invention includes a polynucleotide that comprises a region of at least 15 contiguous nucleotides, more preferably at least about 20 contiguous nucleotides, more preferably at least about 25 contiguous nucleotides, more preferably at least about 35 contiguous nucleotides, more preferably at least about 50 contiguous nucleotides, even more preferably at least about 75 contiguous nucleotides, even more preferably at least about 100 contiguous nucleotides, even more preferably at least about 200 contiguous nucleotides, even more preferably at least about 300 contiguous nucleotides, even more preferably at least about 500 contiguous nucleotides, even more preferably at least about 750 contiguous nucleotides, even more preferably at least about 1000 contiguous nucleotides, even more preferably at least about

1250 contiguous nucleotides, of SEQ ID NO:l, provided that the contiguous nucleotides are not depicted in SEQ ID NO:3 or SEQ ID NO:5.

Another embodiment of the invention is isolated polynucleotides comprising a region of at least about 20 contiguous nucleotides, with the region having at least 91% sequence identity with a sequence depicted in SEQ ID NO: 1. Alternatively, the region may also have 98% sequence identity, preferably 98.5% sequence identity, preferably 99% sequence identity. Alternatively, these regions may comprise at least about 25 contiguous nucleotides, at least about 30 contiguous nucleotides, at least about 50 contiguous nucleotides, at least about 60 contiguous nucleotides, at least about 75 contiguous nucleotides, at least about 100 contiguous nucleotides, at least about 200 contiguous nucleotides, at least about 250 contiguous nucleotides, at least about 300 contiguous nucleotides, at least about 500 contiguous nucleotides, at least about 700 contiguous nucleotides, at least about 1000 contiguous nucleotides, any and each of which can have any of the above-specified degrees of sequence identity. It is understood that these contiguous nucleotide sequences are not depicted in SEQ ID NO: 3 or SEQ ID NO:5.

As known to those of skill in the art, methods for determination of sequence identity between two polynucleotides can include the use of hybridization reactions and sequence alignment algorithms. Alignment of known polynucleotide sequences relative to each other with commercially available sequence comparison programs, such as BLAST programs or those found in the GCG, Inc. software packages, provide a means to directly compare sequences for degree of identity. Such programs establish the sequence alignments and can provide the percentage of sequence identity between them.

Generally, such programs identify the best sequence alignment by scoring the alignment for matches, mismatches, and gaps in the sequence created in the generation of the alignment. For example, the BESTFIT program from GCG uses the algorithm of Smith and Waterman with the default scoring of a match value of 10, a mismatch value of -9, a gap creation penalty of 50 and a gap extension penalty of 3. Thus, the quality score for a polynucleotide alignment can be determined using the equation: Quality = (10 x matches) + (-9 x mismatches) - (50 x gap number) - (3 x total length of gaps) Other alignment programs are based on other algorithms which score alignment with different values (e.g., the GAP program from GCG uses the Needleman and Wunsch algorithm with the default match and gap scoring values as desribed for the BESTFIT program but a default mismatch value of 0 and the FASTA program uses a Pearson and Lipman search with a default gap creation penalty of 16 and gap extension penalty of 4). Similar alignment programs can be used to assess amino acid sequence similarity between polypeptide sequences. Often, the alignment of polypeptide sequences are scored using values different than those used with polynucleotides. For example, the FASTA program uses a default gap creation penalty of J.2 and gap extension penalty of 2. Once the polypeptides are aligned relative to each other, the programs can provide the degree of amino acid similarity and identity. Hybridization can also be used in the determination of polynucleotide sequence identity. The stability of hybridized sequences is reflected in the melting temperature (T_m; discussed below) of the hybrids. For polynucleotides greater than 100 nucleotides in length, the T_m can be used to approximate the degree of sequence identity between two sequences because the T_ra appears to decrease 0.5 - 1.5 °C for every 1% base pair mismatch in the hybrid. This approach can only approximate the degree of identity because the base composition of and mismatch distribution in the hybrids influence the actual change in T_m. Generally, to determine the approximate sequence identity between two polynucleotide sequences with hybridization, the lowest temperature at which hybridization occurs between identical sequences is established for a particular hybridization solution (see below) and the T_m is determined. When the polynucleotide sequence is then hybridized with another sequence, a decrease in the T_m of the reaction can be correlated to the degree of mismatch between the sequences as described above (i.e., roughly 1% degree of mismatch reduces the T_m of a heteroduplex by 0.5 - 1.5 °C).

Hybridization reactions can be performed under conditions of different "stringency". Stringency of hybridization is used herein to refer to conditions under which polynucleotide hybrids are stable. Conditions that increase stringency of a hybridization reaction of widely known and published in the art. See, for example, Sambrook et al. (1989) and Ausubel et al. (1987).

"T_m" is the temperature in degrees Centigrade at which 50% of a polynucleotide duplex made of complementary strands hydrogen bonded in anti-parallel direction by Watson-Crick base pairing dissociates into single strands under conditions of the experiment. T_m may be predicted according to a standard formula, such as: T_m = 81.5 + 16.6 log[X⁺] + 0.41 (%G/C) - 0.61 (%F) - 600/L where [X⁺] is the cation concentration (usually sodium ion, Na⁺) in mol/L; (%G/C) is the number of G and C residues as a percentage of total residues in the duplex; (%F) is the percent formamide in solution (wt/vol); and L is the number of nucleotides in each strand of the duplex. Thus, hybrid stability is dependent upon a number of factors including, but not limited to, ionic strength of the hybridization and wash solutions, base composition of the polynucleotides involved in the duplex; destabilizing agents in the hybridization solution (e.g., formamide or urea),and length of the duplex formed. In terms of hybridization conditions, the higher the sequence identity required, the more stringent are the hybridization conditions if such sequences are determined by their ability to hybridize to a sequence of SEQ ID NO: 1. Accordingly, the invention also includes polynucleotides that are able to hybridize to a sequence comprising at least 20 contiguous nucleotides (or more, such as 25, 35, 50, 75 or 100 contiguous nucleotides) of SEQ ID NO: 1. The hybridization conditions would be stringent, e.g., 80°C (or higher temperature) and 6 X SSC (or less concentrated SSC). Examples of relevant conditions include (in order of increasing stringency): incubation temperatures of 25°C, 37°C, 50°C and 68°C; buffer concentrations of 10 X SSC, 6 X SSC, 1 X SSC, 0.1 X SSC (where 1 X SSC is 0.15 M NaCl and 15 mM citrate buffer) and their equivalents using other buffer systems; formamide concentrations of 0%, 25%, 50%), and 75%; incubation times from 24 hours to 5 minutes; 1, 2, or more washing steps; wash incubation times of 1, 2, or 15 minutes; and wash solutions of 6 X SSC, 1 X SSC, 0.1 X SSC, or deionized water, in temperatures of 25°C, 37°C, 50°C and 68°C.

Accordingly, the invention includes an isolated polynucleotide capable of hybridizing under moderately stringent conditions, more preferably under stringent conditions, to a region of SEQ ID NO: 1 , wherein the region is at least about 10 contiguous nucleotides. The region may also be at least about 25 contiguous nucleotides, at least about 50 contiguous nucleotides, at least about 100 contiguous nucleotides, at least about 150 contiguous nucleotides, at least about 200 contiguous nucleotides, at least about 200 contiguous nucleotides, at least about 300 contiguous nucleotides, at least about 500 contiguous nucleotides, at least about 1000 contiguous nucleotides of a region of SEQ ID

NO:l. The invention also includes an isolated polynucleotide capable of hybridizing under moderately stringent conditions, even more preferably under stringent conditions, to the sequence depicted in SEQ ID NO:l.

Compositions containing mGluR5 polynucleotides are encompassed by this invention. The invention also provides compositions comprising a vector(s) containing an mGluR5 polynucleotide as well as compositions comprising a host cell containing an mGluR5 polynucleotide, as described herein. Generally, the compositions further contain a physiologically acceptable medium, such as water, buffered solutions, or pharmaceutically acceptable excipient. These media are well-known in the art.

The polynucleotides of this invention can be obtained using chemical synthesis, recombinant methods, or PCR.

Methods of chemical polynucleotide synthesis are well known in the art and need not be described in detail herein. One of skill in the art can use the sequences provided herein and a commercial DNA synthesizer to produce a desired DNA sequence.

For preparing mGluR5 polynucleotides using recombinant methods, a polynucleotide comprising a desired sequence can be inserted into a suitable vector, and the vector in turn can be introduced into a suitable host cell for replication and amplification. Polynucleotides may be inserted into host cells by any means known in the art. Cells are transformed by introducing an exogenous polynucleotide by direct uptake, endocytosis, transfection. F-mating or electroporation. Once introduced, the exogenous polynucleotide can be maintained within the cell as a non-integrated vector (such as a plasmid) or integrated into the host cell genome. The polynucleotide so amplified can be isolated from the host cell by methods well known within the art. See, e.g., Sambrook et al. (1989).

Alternatively, PCR allows reproduction of DNA sequences. PCR technology is well known in the art and is described in U.S. Pat. Nos. 4,683,195, 4,800,159, 4,754,065 and 4,683,202, as well as PCR: The Polymerase Chain Reaction, Mullis et al. eds.,

Birkauswer Press, Boston (1994).

RNA can be obtained by using the isolated DNA in an appropriate vector and inserting it into a suitable host cell. When the cell replicates and the DNA is transcribed into RNA, the RNA can then be isolated using methods well known to those of skill in the art, as set forth in Sambrook et al., (1989), for example. RNA can also be obtained through in vitro reactions. For example, the mGluR5 polynucleotide can be inserted into a vector that contains appropriate transcription promoter sequences. Commercially available RNA polymerases will specifically initiate transcription at their promoter sites and continue the transcription process through the adjoining DNA polynucleotides. Placing the mGluR5 polynucleotides between two such promoters allows the generation of sense or antisense strands of mGluR5 RNA.

If used as a vaccine (i.e., pharmaceutical composition for eliciting an immune response), plasmids containing mGluR5 polynucleotides are preferably prepared as described by Horn et al. ((1995) Human Gene Therapy 6:565-573) which produces a pharmaceutical grade plasmid DNA suitable for administration.

Cloning and expression vectors comprising mGluR5 polynucleotide

The present invention further includes a variety of vectors containing mGluR5 polynucleotides of this invention. These vectors can be used for expression of recombinant polypeptides as well as a source of mGluR5 polynucleotides. Cloning vectors can be used to obtain replicate copies of the mGluR5 polynucleotides they contain, or as a means of storing the polynucleotides in a depository for future recovery. Expression vectors (and host cells containing these expression vectors) can be used to obtain polypeptides produced from the polynucleotides they contain. They may also be used where it is desirable to express mGluR5 polypeptides in an individual, such as for eliciting an immune response via the polypeptide(s) encoded in the expression vector(s). Suitable cloning and expression vectors include any known in the art, e.g., those for use in in vitro, bacterial, mammalian, yeast and insect expression systems. Specific vectors and suitable host cells are known in the art and need not be described in detail herein. For example, see Gacesa and Ramji, Vectors, John Wiley & Sons (1994).

Cloning and expression vectors typically contain a selectable marker (for example, a gene encoding a protein necessary for the survival or growth of a host cell transformed with the vector), although such a marker gene can be carried on another polynucleotide sequence co-introduced into the host cell. Only those host cells into which a selectable gene has been introduced will survive and or grow under selective conditions. Typical selection genes encode protein(s) that (a) confer resistance to antibiotics or other toxins substances, e.g., ampicillin, neomycyin, methotrexate, etc.; (b) complement auxotrophic deficiencies; or (c) supply critical nutrients not available from complex media. The choice of the proper marker gene will depend on the host cell, and appropriate genes for different hosts are known in the art. Cloning and expression vectors also typically contain a replication system recognized by the host.

Suitable cloning vectors may be constructed according to standard techniques, or may be selected from a large number of cloning vectors available in the art. While the cloning vector selected may vary according to the host cell intended to be used, useful cloning vectors will generally have the ability Xo self-replicate, may possess a single target for a particular restriction endonuclease, and/or may carry genes for a marker that can be used in selecting clones containing the vector. Suitable examples include plasmids and bacterial viruses, e.g., pUC18, mpl8, mpl9, pBR322, pMB9, ColEl, pCRl, RP4, phage

DNAs, and shuttle vectors such as pSA3 and pAT28. These and many other cloning vectors are available from commercial vendors such as BioRad, Stratagene, and Invitrogen. Expression vectors generally are replicable polynucleotide constructs that contain a polynucleotide encoding an mGluR5 polypeptide of interest. The mGluR5 polynucleotide encoding the polypeptide is operatively linked to suitable transcriptional controlling elements, such as promoters, enhancers and terminators. For expression (i.e., translation), one or more translational controlling elements are also usually required, such as ribosome binding sites, translation initiation sites, and stop codons. These controlling elements (transcriptional and translational) may be derived from the mGluR5 gene, or they may be heterologous (i.e., derived from other genes and/or other organisms). A polynucleotide sequence encoding a signal peptide can also be included to allow an mGluR5 polypeptide to cross and/or lodge in cell membranes or be secreted from the cell. A number of expression vectors suitable for expression in eukaryotic cells including yeast, avian, and mammalian cells are known in the art. Another example of an expression vector (system) is the baculovirus/insect cell system. Expression of mGluR5 RNA in vitro is described above. The vectors containing the polynucleotides of interest can be introduced into the host cell by any of a number of appropriate means, including electroporation, transfection employing calcium chloride, rubidium chloride, calcium phosphate, DEAE-dextran, or other substances; microprojectile bombardment; lipofection; and infection (where the vector is an infectious agent, such as vaccinia virus). The choice of means of introducing vectors or mGluR5 polynucleotides will often depend on the host cell.

Host cells transformed with mGluR5 polynucleotides

Another embodiment of this invention are host cells transformed with (i.e., comprising) mGluR5 polynucleotides and/or vectors having mGluR5 polynucleotide(s) sequences, as described above. Both prokaryotic and eukaryotic host cells may be used. Prokaryotic hosts include bacterial cells, for example E. coli, B. subtilis, and mycobacteria.

Among eukaryotic hosts are yeast, insect, avian, plant, C. elegans (or nematode) and mammalian cells. Host systems are known inJhe art and need not be described in detail herein. Examples of fungi (including yeast) host cells are S. cerevisiae, Kluyveromyces lactis (K. lactis), species of Candida including C. albicans and C. glabrata, Aspergillus nidulans, Schizosaccharomyces pombe (S. pombe), Pichia pastoris, and Yarowia lipolytica.

Examples of mammalian cells are COS cells, house L cells, Chinese hamster ovary (CHO) cells, human embroyonic kidney (HEK) cells, African green monkey cells. Xenopus laevis oocytes, or other cells of amphibian origin, may also be used.

The host cells of this invention can be used, inter alia, as repositories of mGluR5 polynucleotides and/or vehicles for production of mGluR5 polynucleotides and/or polypeptides. They may also be used in the screening methods described above. Polypeptides of the invention

The present invention encompasses mouse mGluR5 polypeptide sequences. Unless specifically stated, the term "polypeptide(s)" shall include all polypeptide embodiments of this invention. It is also further understood that polypeptide embodiments of this invention are isolated polypeptides.

The polypeptides have a variety of uses, including their use in making antibodies that bind to these polypeptides, their use as agents to screen pharmaceutical candidates (both in vitro and in vivo), and their use in rational (i.e., structure-based) drug design. The mGluR5 polypeptides may also be used to identify proteins that interact physically with mGluR5 which could thus themselves be drug targets.

The amino acid sequence of mGluR5 is shown in SEQ ID NO:2. The publicly available conceptual translation of SEQ ID NO:3 (depicted in SEQ ID NO:4) does not correspond to any region of the conceptual translation of SEQ ID NO:l (as depicted in SEQ ID NO:2). In one embodiment, the invention includes an isolated polypeptide comprising at least about 5 contiguous amino acids of the sequence of SEQ ID NO:2, wherein the about 5 contiguous amino acids are not depicted in SEQ ID NO:6 or in SEQ ID NO:7, and wherein the isolated polypeptide exhibits an mGluR5 function. In this context, "mGluR5 function" includes, not only those functions delineated in the "Definitions" section of this application, but other functions such as ability to elicit an immune response, including a humoral and/or cellular immune response. In other embodiments, the isolated polypeptide comprises at least about 10 contiguous amino acids, at least about 15 contiguous amino acids, at least about 20 contiguous amino acids, at least about 25 contiguous amino acids, at least about 30 contiguous amino acids, at least about 50 contiguous amino acids, at least about 75 contiguous amino acids, at least about 100 contiguous amino acids, at least about 150 contiguous amino acids, at least about 200 contiguous aminoacids, at least about 250 contiguous amino acids, at least about 300 contiguous amino acids, at least about 400 contiguous amino acids, at least about 500 contigous amino acids of the sequence of SEQ ID NO:2. In any or all of these instances, the contiguous amino acids are not depicted in SEQ ID NO:6 or SEQ ID NO:7. In another embodiment, the invention includes an isolated polypeptide comprising an mGluR5 polypeptide , wherein the polypeptide comprises the sequence of SEQ ID NO:2.

In another embodiment, the invention provides an isolated polypeptide comprising at least 10 contiguous amino acids which have at least 97% sequence identity to a sequence depicted in SEQ ID NO:2. In other embodiments, the isolated polypeptide comprises at least at least about 15 contiguous amino acids, at least about 20 contiguous amino acids, at least about 25 contiguous amino acids, at least about 30 contiguous amino acids, at least about 50 contiguous amino acids, at least about 75 contiguous amino acids, at least about 100 contiguous amino acids, at least about 150 contiguous amino acids at least about 200 contiguous aminoacids, at least about 250 contiguous amino acids, at least about 300 contiguous amino acids, at least about 400 contiguous amino acids, at least about 500 contigous amino acids, any of which having at least a 98%, preferably at least about 98.5%, preferably at least about 99% sequence identity to a sequence of SEQ ID NO:2. In any or all of these instances, the contiguous amino acids are not depicted in SEQ ID NO:6 or SEQ ID NO:7.

Determination of sequence identity in the context of polypeptide sequences generally involves alignment programs readily and commercially available, and have been discussed above. The size of mGluR5 polypeptides may vary widely, as the length required to effect activity could be as small as, for example, a 5- or 10-mer amino acid sequence to effect binding and trigger a response. The maximum length generally is not detrimental to effecting activity. The minimum size must be sufficient to provide a desired function. Thus, the invention includes polypeptide fragments of mGluR5 comprising a portion of the amino acid sequence depicted in SEQ ID NO:2 in which the mGluR5 polypeptide is about 15, preferably

25, more preferably 50 more preferably 75, more preferably 100 amino acids in length. These lengths could depend on the proposed use of the mGluR5 polypeptide; for example, a polypeptide comprising the transmembrane domain of mGluR5 could be desired, or the extracellular and or intracellular domain. Based on the amino acid sequence, and what is known about domains of other mGluRs, these domains could be estimated. Alternatively, it may be that only a partial extracellular domain is necessary if binding of glutamate is the desired function. As noted above, only a relatively small polypeptide could be used if binding to antibody or eliciting an immune response is desired.

As is evident to one skilled in the art, these mGluR5 polypeptides. regardless of their size, may also be associated with, or conjugated with, other substances or agents to facilitate, enhance, or modulate function and/or specificity of an mGluR5 polypeptide.

The invention includes modifications to mGluR5 polypeptides including functionally equivalent fragments of the mGluR5 polypeptides which do not significantly affect their properties and variants which have enhanced or decreased activity. Collectively, these modifications may be termed "analogs" of mGluR5 or a fragment of mGluR5. Modification of polypeptides is routine practice in the art and need not be described in detail herein. Examples of modified polypeptides include polypeptides with conservative substitutions of amino acid residues, one or more deletions or additions of amino acids which do not significantly deleteriously change the functional activity, or use of chemical analogs. Amino acid residues which can be conservatively substituted for one another include but are not limited to: glycine/alanine; valine/isoleucine/leucine; asparagine/glutamine; aspartic acid/glutamic acid; serine/threonine; lysine/arginine; and phenylalanine/tryosine. Such conservative substitutions are known in the art, and preferably, the amino acid substitutions would be such that the substituted amino acid would possess similar chemical properties as that of the original amino acid. These polypeptides also include glycosylated and non-glycosylated polypeptides, as well as polypeptides with other post-translational modifications, such as, for example, glycosylation with different sugars, acetylation, and phosphorylation. Amino acid modifications can range from changing or modifying one or more amino acids to complete redesign of a region. Other methods of modification include using coupling techniques known in the art, including, but not limited to, enzymatic means, oxidative substitution and chelation. Modifications can be used, for example, for attachment of labels for immunoassay, such as the attachment of radioactive moieties for radioimmunoassay. Modified mGluR5 polypeptides are made using established procedures in the art and can be screened using standard assays known in the art. The invention also encompasses fusion proteins comprising one or more mGluR5 polypeptides. For purposes of this invention, an mGluR5 fusion protein contains one or more mGluR5 polypeptides and another amino acid sequence to which it is not attached in the native molecule, for example, a heterologous sequence or a homologous sequence from another region. Useful heterologous sequences include, but are not limited to, sequences that provide for secretion from a host cell, enhance immunological reactivity, or facilitate the coupling of the polypeptide to an immunoassay support or a vaccine carrier. For instance, an mGluR5 polypeptide can be fused with a bioresponse modifier. Examples of bioresponse modifiers include, but are not limited to, cytokines or lymphokines such as GM-CSF, interleukin-2 (IL-2), interleukin 4 (IL-4), and γ-interferon. Accordingly, the invention includes mGluR5 fusion polypeptides that contain GM-CSF or IL-2. Another useful heterologous sequence is one which facilitates purification. Examples of such sequences are known in the art and include those encoding epitopes such as Myc, HA

(derived from influenza virus hemagglutinin), His-6, or FLAG. Other heterologous sequences that facilitate purification are derived from proteins such as glutathione S- transferase (GST), maltose-binding protein (MBP), or the Fc portion of immunoglobulin. Another useful heterologous sequence is a functional domain which can substitute for a functional domain of mGluR5. For example, a chimeric receptor could be constructed in forder to functionally isolate aspects of mGluR5. See, for example, WO 97/05252.

In another embodiment, mGluR5 polypeptides can be conjugated with carrier or label. For example, in instances where the mGluR5 polypeptide is correctly configured so as to provide a binding site, but is too small to be immunogenic, the polypeptide may be linked to a suitable carrier. A number of techniques for obtaining such linkage are known in the art and need not be described in detail herein. Any carrier can be used which does not itself induce the production of antibodies harmful to the host. Suitable carriers are typically large, slowly metabolized macromolecules such as proteins; polysaccharides, such as latex functionalized sepharose, agarose, cellulose, cellulose beads and the like; polymeric amino acids, such as polyglutamic acid, polylysine, and the like; amino acid copolymers; and inactive virus particles or attenuated bacteria, such as Salmonella. Especially useful protein substrates are serum albumins, keyhole limpet hemacyanin, immunoglobulin molecules, thyroglobulin, ovalbumin, tetanus toxoid, and other proteins well known to those of skill in the art. Labels are known in the art and are described herein.

Compositions containing mGluR5 polypeptides are also encompassed by this invention. When these compositions are to be used pharmaceutically, they are combined with a pharmaceutically acceptable excipient. The compositions may alternatively or additionally contain a physiologically acceptable medium, examples of which have been provided above. mGluR5 polypeptides of the invention can be identified and/or characterized in a number of ways. For example, an mGluR5 polypeptide can be tested for its ability to bind to, for instance, another protein (such as an antibody or ligand, such as glutamate). Alternatively, mGluR5 polypeptide(s) can be tested for its ability to elicit an immune response, whether humoral or cellular. It is understood that only one of these properties need be present in order for a polypeptide to come within this invention, although more than one of these properties may be present.

The ability of an mGluR5 polypeptide to bind (i.e., interact with) another protein can be assessed using standard techniques in the art. Binding of an mGluR5 polypeptide to an antibody may be assessed, for example, by RIA (i.e., by reacting radiolabeled mGluR5 polypeptide with an antibody that is coated on microtiter plates). In another procedure, binding to an antibody is determined by competitive immunoassay. For example, a fragment is tested for its ability to interfere with the binding between the antibody and another polypeptide known to bind to the antibody. This assay may be conducted by labeling one of the components (i.e., antibody or polypeptide known to bind to the antibody), and optionally immobilizing the other member of the binding pair on a solid support for ease of separation. The test fragment is incubated with labeled region, and then the mixture is presented to the immobilized target to determine if the test fragment is able to inhibit binding.

In the case of testing whether the mGluR5 polypeptide binds to another protein, for instance, a ligand, assays to detect binding are known in the art and need not be described in detail herein. For instance, a protein is immobilized on a suitable column. Extracts or solutions containing the test mGluR5 polypeptide are then run through the column, and a determination is made whether the mGluR5 polypeptide was retained on the column. Conversely, the mGluR5 polypeptides can be immobilized on a column and cell extracts or lysates are allowed to run through the column. Alternatively, the two hybrid technique can be used to identify polypeptides that interact with mGluR5 polypeptides (as well as, the cDNAs that encode such polypeptides) and to test such interactions. Brent et al. U.S. Pat. No. 5,580,736. For characterizing an mGluR5 polypeptide for its ability to elicit an immune response (whether humoral or cellular) in an individual, standard assays exist in the art. For instance, the ability of an mGluR5 polypeptide to generate a humoral response can be determined by testing for the presence of an antibody that binds to the mGluR5 polypeptide(s) after administration of the mGluR5 polypeptide(s). It is understood that this antibody was not present, or was present in lower amounts, before administration of the mGluR5 polypeptide(s). Immunogenicity is preferably tested in individuals without a previous anti- mGluR5 response. Examples of suitable individual include, but are not limited to, mice, rats, rabbits, goats, monkeys and humans. For this test, an individual is administered an mGluR5 polypeptide(s). The amount per administration and the number of administrations will vary, depending on the individual. Presence of an antibody elicited in response to administration of an mGluR5 polypeptide(s) is determined by standard assays in the art, such as ELISA or RIA. mGluR5 polypeptide(s) may be further characterized by their ability to elicit an antibody that is cytotoxic, or to elicit an antibody that participates in an ADCC response using standard assays in the art.

A mGluR5 polypeptide can also be characterized by its ability to elicit a cellular immune response, using, for example, assays that detect proliferation of peripheral blood mononuclear cells (PBMs) incubated with an mGluR5 polynucleotide. Another way of detecting a cellular immune response is to test for T cell cytotoxicity (CTL) activity. Both of these responses are detected using standard assays in the art.

Other measurable activities may be used to characterize an mGluR5 polypeptide, such as membrane association, particular conformational change upon binding agonist(s) or antagonist(s), and ability to prevent or reduce signal transduction when expressed in a suitable host cell. Preparation of polypeptides of this invention

The polypeptides of this invention can be made by procedures known in the art. The polypeptides can be produced by recombinant methods (i.e., single or fusion polypeptides) or by chemical synthesis. Polypeptides, especially shorter polypeptides up to about 50 amino acids, are conveniently made by chemical synthesis. Methods of chemical synthesis are known in the art and are commercially available. For example, a polypeptide could be produced by an automated polypeptide synthesizer employing the solid phase method. Polypeptides can also be made by chemical synthesis using techniques known in the art.

Polypeptides can also be made by expression systems, using recombinant methods. The availability of polynucleotides encoding polypeptides permits the construction of expression vectors encoding intact (i.e., native) polypeptide, functionally equivalent fragments thereof, or recombinant forms. A polynucleotide encoding the desired polypeptide, whether in fused or mature form, and whether or not containing a signal sequence to permit secretion, may be ligated into expression vectors suitable for any convenient host. Both eukaryotic and prokaryotic host systems can be used. The polypeptide is then isolated from lysed cells or from the culture medium and purified to the extent needed for its intended use. Purification or isolation of the polypeptides expressed in host systems can be accomplished by any method known in the art. For example, cDNA encoding a polypeptide intact or a fragment thereof can be operatively linked to a suitable promoter, inserted into an expression vector, and transfected into a suitable host cell. The host cell is then cultured under conditions that allow transcription and translation to occur, and the desired polypeptide is recovered. Other controlling transcription or translation segments, such as signal sequences that direct the polypeptide to a specific cell compartment (i.e., for secretion), can also be used. Examples of prokaryotic host cells are known in the art and include, for example, E. coli and B. subtilis. Examples of eukaryotic host cells are known in the art and include yeast, avian, insect, plant, nematode, and animal cells such as COS7, HeLa, CHO and other mammalian cells.

When using an expression system to produce mGluR5 polypeptides, it is often preferable to construct a fusion protein that facilitates purification. Examples of components for these fusion proteins include, but are not limited to myc, HA, FLAG, His- 6, glutathione S-transferase, maltose binding protein or the Fc portion of immunoglobulin.

These methods are known in the art.

Alternatively, in vitro expression systems may also be used to produce mGluR5 polypeptides. A plasmid containing an mGluR5 polynucleotide, under the control of an appropriate promoter, can be transcribed and the resultant RNA translated in vitro through the use of commercially available reagents. Such methods can be used to produce relatively pure, although small amounts of the polypeptide and are known in the art. Preferably, especially if used for diagnostic purposes, the polypeptides are at least partially purified from other cellular constituents. Preferably, the polypeptides are at least 50% pure. In this context, purity is calculated as a weight percent of the total protein content of the preparation. More preferably, the proteins are 50-75% pure. More highly purified polypeptides may also be obtained and are encompassed by the present invention.

For clinical use, the polypeptides are preferably highly purified, at least about 80% pure, and free of pyrogens and other contaminants. Methods of protein purification are known in the art and are not described in detail herein.

Antibodies of the invention

Also provided by this invention are antibodies capable of specifically binding to mGluR5 polypeptide(s) of this invention. The antibodies can be useful for, for example, for detecting and characterizing mGluR5 polypeptides, as described above. Antibodies of this invention can also be used for purification and/or isolation of polypeptides described herein.

In one embodiment, the invention provides a purified antibody capable of specifically binding to a polypeptide of this invention. As noted in the definition of "antibody" above, this includes fragments of antibodies, such as Fab fragments. In another embodiment, a monoclonal antibody is provided that is capable of specifically binding to a polypeptide of this invention.

Laboratory methods for producing polyclonal antibodies and monoclonal antibodies, as well as deducing their corresponding nucleic acid sequences, are known in the art. For example, see Harlow and Lane, Antibodies: A Laboratory Manual, Cold Spring Harbor Laboratory, New York (1988) and Sambrook et al. (1989). The antibodies of this invention may be polyclonal or monoclonal. Monoclonal antibodies of this invention can be biologically produced by introducing a polypeptide (or fragment of a polypeptide) of this invention into an animal, e.g., mouse or rat . The antibody producing cells in the animal are isolated and fused with myeloma cells or heteromyeloma cells to produce hybrid cells or hybridomas. Accordingly, the invention also includes hybridoma cells producing the monoclonal antibodies of this invention.

Particular isotypes of a monoclonal antibody can be prepared either directly by selecting from the initial fusion, or prepared secondarily, from a parental hybridoma secreting a monoclonal antibody of different isotype by using the sib selection technique to isolate class switch variants using the procedure described in Steplewski et al. (1985) Proc. Natl. Acad. Sci. 82:8653 or Spira et al. (1984) J. Immunol. Methods 74:307.

Thus, using the polypeptide(s) of this invention or fragment(s) thereof, and well known methods, one of skill in the art can produce and screen the hybridoma cells and antibodies of this invention for antibodies having the ability to bind polypeptide(s) of this invention.

If a monoclonal antibody being tested binds with an mGluR5 polypeptide(s) of this invention, then the antibody being tested and the antibodies provided by the hybridomas of this invention are equivalent. It is also possible to determine without undue experimentation whether an antibody has the same specificity as a monoclonal antibody of this invention by determining whether the antibody being tested prevents a monoclonal antibody of this invention from binding the polypeptide(s) with which the monoclonal antibody is normally reactive. If the antibody being tested competes with the monoclonal antibody of the invention as shown by a decrease in binding by the monoclonal antibody of this invention, then it is likely that the two antibodies bind to the same or a closely related epitope. Alternatively, one can pre-incubate the monoclonal antibody of this invention with the polypeptide(s) with which it is normally reactive, and determine if the monoclonal antibody being tested is inhibited in its ability to bind the antigen. If the monoclonal antibody being tested is inhibited, then, in all likelihood, it has the same, or a closely related, epitopic specificity as the monoclonal antibody of this invention.

As noted above, this invention also provides biological active fragments of the polyclonal and monoclonal antibodies described above. These antibody fragments retain some ability to selectively bind with its antigen or immunogen. Examples of antibody fragments are known in the art and include, but are not limited to, CDR regions, Fab, Fab',

F(ab')₂, Fy, and single chain methods. Methods of making these fragments are known in the art, see for example, Harlow and Lane, (1988).

The antibodies of this invention also can be modified to create chimeric antibodies and humanized antibodies (Oi et al. (1986) BioTechniques 4(3):214). Chimeric antibodies are those in which the various domains of the antibodies' heavy and light chains are coded for by DNA from more than one species. The isolation of other hybridomas secreting monoclonal antibodies with the specificity of the monoclonal antibodies of the invention can also be accomplished by one skilled in the art by producing anti-idiotypic antibodies (Herlyn, et al. (1986) Science, 232:100). An anti-idiotypic antibody is an antibody which recognizes unique determinants present on the monoclonal antibody produced by the hybridoma of interest. These determinants are located in the hypervariable region of the antibody. It is this region which binds to a given epitope and, thus, it is responsible for the specificity of the antibody. The anti-idiotypic antibody can be prepared by immunizing an animal with the monoclonal antibody of interest. The animal immunized will recognize and respond to the idiotypic determinants of the immunizing antibody by producing an antibody to these idiotypic determinants. By using the anti-idiotypic antibodies of the second animal, which are specific for the monoclonal antibodies produced by a single hybridoma which was used to immunize the second animal, it is now possible to identify other clones with similar idiotypes as the antibody of the hybridoma used for immunization. Idiotypic identity between monoclonal antibodies of two hybridomas demonstrates that the two monoclonal antibodies are the same with respect to their recognition of the same epitopic determinant. Thus, by using antibodies to the epitopic determinants on a monoclonal antibody it is possible to identify other hybridomas expressing monoclonal antibodies of the same epitopic specificity. It is also possible to use the anti-idiotype technology to produce monoclonal antibodies which mimic an epitope. For example, an anti-idiotypic monoclonal antibody made to a first monoclonal antibody will have_.a binding domain in the hypervariable region which is the mirror image of the epitope bound by the first monoclonal antibody. Thus, in this instance, the anti-idiotypic monoclonal antibody could be used for immunization for production of these antibodies.

The antibodies of this invention can be linked (i.e., conjugated) to a detectable agent or a hapten. The complex is useful to detect the polypeptide(s) (or polypeptide fragments) to which the antibody specifically binds in a sample, using standard immunochemical techniques such as immunohistochemistry as described by Harlow and Lane (1988). supra. Examples of types of immunoassays which can utilize monoclonal antibodies of the invention are competitive and non-competitive immunoassays in either a direct or indirect format. Examples of such immunoassays are the enzyme linked immunoassay (ELISA) radioimmunoassay (RIA) and the sandwich (immunometric) assay. Detection of using the monoclonal antibodies of the invention can be done by utilizing immunoassays which are run in either the forward, reverse, or simultaneous modes, including immunohistochemical assays on physiological samples. Those of skill in the art will know, or can readily discern, other immunoassay formats without undue experimentation.

Another technique which may also result in greater sensitivity consists of coupling the antibodies to low molecular weight haptens. These haptens can then be specifically detected by means of a second reaction. For example, it is common to use such haptens as biotin, which reacts avidin, or dinitropherryl, pyridoxal, and fluorescein. which can react with specific anti-hapten antibodies. See Harlow and Lane (1988) supra.

The monoclonal antibodies of the invention can be bound to many different carriers. Thus, this invention also provides compositions containing antibodies and a carrier. Carriers can be active and/or inert. Examples of well-known carriers include glass, polystyrene, polypropylene, polyethylene, dextran, nylon, amylases, natural and modified celluloses, polyacrylamides, agaroses and magnetite. The nature of the carrier can be either soluble or insoluble for purposes of the invention. Those skilled in the art will know of other suitable carriers for binding monoclonal antibodies, or will be able to ascertain such, using routine experimentation.

There are many different labels and methods of labeling known to those of ordinary skill in the art. Examples of the types of labels which can be used in the present invention include enzymes, radioisotopes, fluorescent compounds, colloidal metals, chemiluminescent compounds, and bioluminescent compounds. Those of ordinary skill in the art will know of other suitable labels for binding to the monoclonal antibody, or will be able to ascertain such, using routine experimentation. Furthermore, the binding of these labels to the monoclonal antibody of the invention can be done using standard techniques common to those of ordinary skill in the art.

For purposes of the invention, mGluR5 polypeptides of this invention may be detected by the monoclonal antibodies of the invention by their ability to bind these antibodies. Compositions containing the antibodies, fragments thereof or cell lines which produce the antibodies, are encompassed by this invention. When these compositions are to be used pharmaceutically, they are combined with a pharmaceutically acceptable excipient. The compositions may alternatively or additionally contain a physiologically acceptable medium, examples of which have been provided above.

The following examples are provided to illustrate but not limit the invention.

EXAMPLES

Example 1: Differential effect of CNS depressant propofol on LS and SS mice

Methods

Experimental protocols were approved by our animal care committee. Male LS and SS mice were provided by the Institute for Behavioral Genetics, University of Colorado,

Boulder. They were of the 54^th generation (25^th generation of selection), were weaned at 25d, and were drug tested at 60-90 d.

Right-sided jugular venous cannulas were implanted under intraperitoneal pentobarbital (60 mg/kg)-chloral hydrate (125 mg/kg) anesthesia on Day 1. Mice were allowed to rest for 2 d and propofol testing took place on Day 3. Propofol formulated in

Intralipid (10 mg/kg) was obtained from Stuart Chemicals (Wilmington, DE) and administered intravenously via the jugular cannula. Injected volumes ranged from 30 to 70 μl and were given over 30-45 s by Hamilton syringe. Doses appropriate for loss of righting reflex ranged from 10 to 35 mg/kg. Saline flush was administered after propofol to bring the total injectate to 100 μl. The loss of righting reflex was immediate in all cases.

Animals were placed on their backs in V-shaped Plexiglas troughs and judged awake upon regaining the righting reflex (ability to turn over three times in 1 min).

Propofol levels at awakening were determined in brain cortex and plasma samples. The method of intravenous propofol dosing was simplified by administering 20 mg/kg propofol via the retroorbital venous sinus using a 28-gauge needle and Hamilton syringe.

Injected volumes ranged from 40 to 50 μL and were given over 30 s. At awakening, cortical brain and body cavity samples were collected. Blood samples were pooled and centrifuged at 3000g- for 15 min; plasma was collected and stored at 4° C until analysis by gas chromatography. Brain samples were weighed and stored until analysis by gas chromatography. The method of Yu and Liau was used for determination of brain and plasma levels by gas chromatographic analysis. J. Chromatog. (1993) 615:77-81. 2-sec- Butylphenol was used as an internal standard. ³⁶C1^" uptake was performed using freshly prepared mouse brain microsacs as described previously. Allan and Harrris (1986) Life Sci. 39:2005-2015. Brain cortices were manually homogenized in a glass Teflon homogenizer. Homogenizing solution was 4.5 mL of ice-cold assay buffer containing (mM) NaCl 145, KC1 5, MgCl₂ 1, d-glucose 10, CaCl₂ 1, and HEPES 10, adjusted to pH 7.5 with Tris base. The homogenate was centrifuged at 900g for 15 min, the supernatant decanted, and the pellet resuspended in 8 mL of assay buffer. It was then centrifuged again at 900g for 15 min. The final pellet was suspended in 7 mL of assay buffer. Protein concentrations were determined by the method ofLowery et al. J. Biol. Chem. (1951) 193:265-275. Propofol stimulated ³⁶C1^" uptake was maximized in the following way: aliquots of microsacs (200 μL) were incubated in a shaking water bath at 34°C for 5 min. ³⁶C1^" uptake was initiated by addition of 200 uL of a solution containing ³⁶C1^" (2 μCi/mL). Muscimol (2 μM) and propofol were added in the ³⁶C1^' solution. ³⁶C1^" influx was terminated after a 3-s incubation period by addition of 4 mL of ice-cold buffer and rapid filtration under vacuum onto Whatman GF/C glass microfiber filters. Filters were washed with an additional 8 mL of cold buffer. Radioactivity retained on filters was determined by liquid scintillation spectrometry. Control values were obtained using only Intralipid in the preparation. Blank values (no tissue in preparation) were subtracted from all final values. Muscimol- dependent uptake was defined as the amount of ³⁶C1^" taken up with agonist present in the medium minus the amount of ³⁶C1^* taken up while agonist was absent (muscimol- independent uptake). Propofol-stimulated uptake was calculated as the uptake in the presence of propofol plus muscimol minus the-uptake in the presence of muscimol alone. Student's unpaired t-test was used for comparisons of mean sleep times and drug levels. The ⁶C1^" uptake of brain microsacs was compared at several different propofol concentrations using analysis of variance. Statistical significance was set at P < 0.05.

Results

Propofol produced dose-dependent increases in sleep times for both LS and SS mice as shown in Figure 1. The LS mice clearly displayed increased sensitivity to propofol, as manifested by longer sleep times, compared with SS mice at every dose. Plasma and cortical brain levels of propofol at awakening were measured and found to be different in the LS and SS mice (P < 0.0001). The LS mice had threefold greater plasma levels and twofold greater brain levels than did the SS mice as shown in Table 1. Propofol plasma levels are expressed in μg/mL plasma ± SD. Propofol brain levels are expressed in μg/g tissue ± SD. A propofol dose of 20 mg/kg was given by retroorbital sinus injection. For both comparative measurements, there was a P < 0.0001 significant difference between means of LS and SS lines.

Table 1. Propofol Plasma and Brain Levels at Awakening in Long Sleep (LS) and Short Sleep (SS) Mice

Tissue LS^~(«) SS^~(tt)

Plasma 4.52 ± 0.91 (9) 13.3 ± 1.15 (9)

Brain 8.05 + 0.9 (13) 16.0 ± 2.4 (15)

The method of propofol dosing was changed from the jugular route (JUG) via the previously implanted catheter to retroorbital venous sinus (ROS) injections using an intravenous dose of 20 mg/kg. We found that the JUG method added several days to a single experiment, produced significant mortality associated with the surgical procedure, and added a prior exposure to the general anesthetics needed to implant the jugular catheter. The ROS method circumvented all these problems. Figure 2 shows the results comparing each of these administrations in SS and LS mice. Although there was a statistically significant difference in sleep times (P < 0.02) in the SS line using JUG dosing versus ROS dosing, the difference was only 1.2 min. (Figure 2). A similar but nonsignificant difference of 1.4 min. was observed in the LS line. The difference in sleep time between the SS and LS lines remained very significant (P < 0.0005). For both lines, the sleep times were somewhat shorter using JUG dosing as compared to ROS dosing. SS sleep time means ±SD were 2.24 ±0.51 min. (JUG) and 3.45 ± 1.02 min. (ROS). LS sleep time means were 4.41 ± 1.29 min. (JUG) and 5.66 ± 1.48 min. (ROS).

We then tested effects of increased propofol on muscimol-stimulated ³⁶C1^" uptake in LS and SS mice. The results are shown in Figure 3. Propofol produced a concentration- dependent enhancement of muscimol-stimulated ³⁶C1^" uptake by membrane vesicles

(microsacs) prepared from mouse cortical brain. (Figure 3) However, there was no significant difference noted between LS and SS brain preparations in the increase in muscimol-stimulated ³⁶C1^" uptake at any of the propofol concentrations. Significant differences in mean ³⁶C1^' uptake were observed between doses by differed by 100-fold concentrations. Propofol concentrations ranged from 0.50 to 50 μmol/L (corresponding to brain levels of 0.32-31.6 μg/mL). Propofol did not affect basal uptake of ³⁶C1^" except at the highest concentration tested (50 μmol/L), which increased basal uptake by about 25%.

Example 2: Mapping CNS depressant sensitivity

In the absence of a biochemical hypothesis to explain the LS and SS difference, we used a positional cloning strategy to determine the location of the locus (or loci) contributing to this activity.

Materials and Methods Origin of Mice

ILS, ISS, and LSXSS RI mice were provided by the Institute for Behavioral Genetics, University of Colorado at Boulder. ILS and ISS have been derived by 20 rounds of brother-sister mating from the LS and SS selected lines; the LSXSS RI set was similarly derived after reciprocal intercrosses between LS and SS, prior to the LS and SS having been inbred. Market et al. (1996); DeFries et al. (1989) Alcohol Clin Exp Res 13:196-200. Thus the progenitors of the LSXSS RIs and the F intercross are not the same stock and could have some differences affecting sensitivity to propofol. Animals were bred in a specific-pathogen free facility, weaned at about 25 days and housed 1 -4 per cage with like- sex littermates on a 12-hour light/dark cycle. Experimental protocols were approved by animal care and use committees at the University of Colorado at Boulder and University of Colorado Health Sciences Center at Denver. For the LSXSS RIs, between 5 and 15 mice of each sex were tested per strain. For the ILS x ISS F₂s, 194 mice were tested for LORR and 164 subsequently genotyped. C57BL/6J coisogenic mice having the spontaneous albino mutation c^2J were obtained from Jackson Laboratory, Bar Harbor, Maine. Phenotypic Assessments

Propofol (10 mg/ml in Intralipid, Stuart Chemicals) injections were performed when mice were 60 to 94 days of age. Dosages of 20 mg/kg (volumes ranging from 30-70 μl) were administered by injection into the retroorbital venous sinus using a 26-gauge, 3/8- inch needle and Hamilton syringe. Sensitivity to propofol was assessed using the duration of loss of righting reflex (LORR). Simpson et al. (1996). Upon injection, mice immediately lost consciousness and were placed on their back in V-shaped Plexiglass troughs until recovery of righting reflex. Animals were judged to have regained the righting reflex when they turned over three times in less than a minute. Temperature was controlled at 24-26°C. Full recovery was quick after regaining consciousness, as typically observed in recovery from propofol anesthesia in humans; after the first righting, there was almost no delay in the mouse's ability to right a second and third time. The RI and F₂ mice were naive to any previous injections and were injected only once with propofol. LORRs of the (ISS c/c x C57BL/6 C^2JIC) Fi mice represent the mean of two propofol injections spaced seven days apart whose means were not significantly different (p = 0.36, ANOVA two-tailed significance). The brain levels of propofol at awakening (BLA) for the RIs were determined in pooled samples of brain cortex using gas chromatography, as previously described by Simpson and Blednov (1996). Marker Assessments DNA was extracted and purified from spleen, kidney, or liver using a Super-Quik Gene DNA Isolation Kit (AGTC Research). The Mit SSLP primers were obtained from

Research Genetics and the PCR was carried out as previously described. Markel et al. (1994) Mam. Genome 5:199-202. Coat color was scored by eye on living mice; pigmented RI mice were homozygous C/C and albino RI mice were homozygous c/c. Jackson et al. (1984) Proc. Natl. Acad. Sci. 87:7010-14. (This locus was renamed Tyr because it encodes tyrosinase, an enzyme responsible for pigmentation in mammals. See Beerman et al.

(1990) EMBO J. 9:2819-2826; Yokoyama et al. (1990) Nucl. Acids Res. 18:7293-7298).) Statistical Analyses

Broad-sense heritability involves genetic effects arising from dominant, additive and between-gene interactions while narrow-sense heritability involves only additive effects; thus broad-sense heritability is more inclusive and should be a larger fraction than narrow sense. Narrow-sense heritability in the RIs was estimated as 100% x 0.5 σ²β/(σ² + 0.5σ²β), in which σ²β is the between-strain component of variance and σ² is the within- strain component of variance. Falconer (1981) Quantitative Genetics, Ronald, New York. Broad sense heritability was estimated from the ILS by ISS F₂s as 100%) x (V_F2 - V_FI)/V_F2, where V_F2 is the variance of the F₂ population and Vpi represents an average variance calculated from the F|, ILS, and ISS variances. The QTL maps in Figures 2 and 3 were anchored using map positions from the Mouse Genome Database (MGD) map (http://www.informatics.jax.org/mgd.html) of 44.0 for e and D7 t31, whereas the positions of other SSLP markers (Copeland et al. (1993) Science 262:57-66; Dietrich et al. (1994) Nature Genet. 7:220-225; Dietrich et al. (1996) Nature 380:149-152) relative to these were based on the Whitehead Institute/MIT Center for Genome Research (WI MIT CGR) map (http://www.genome.wi.mit.edu), which is the more recently updated and more accurate map regarding the relative position of SSLP markers in this region. Rikke et al. (1997) Genetics 147:787-799. The RJ map was constructed using an interval-mapping procedure previously described by Markel et al. (1996) Behav. Genet. 26:447-458. The F₂ linkage map was constructed using Mapmaker 3.0 and QTL mapping was done using Mapmaker/QTL Version 1.1.

Results

Heritability of Propofol Sensitivity

The results are shown in Table 2. For each population or cross, the female parent is listed first. There was a significant difference in sensitivity to propofol between the LS and SS lines (p « .001 ; Table 2, lines 1, 2), as described in Example 1 (and previously reported by Simpson et al. (1996)); their inbred derivatives, ILS (LORR of 7.4 minutes) and ISS (LORR of 3.8 minutes), also are differentially sensitive to propofol (p « .001; Table 2, lines 3, 4). The ILS and ISS strains were also significantly different from the two Fi reciprocal populations with respect to propofol sensitivity. The Fi showed no statistically significant differences (Table 2, lines 5, 6; p = 0.08, one-tailed) resulting from the maternal parent, thus indicating a lack of maternal effects for sensitivity to propofol. The mean LORR of the Fi was almost intermediate between the two parents but showed slight dominance of the LS allele.

Table 2. Duration of loss of righting reflex (LORR) after propofol injection in various mouse populations.

Population Trait Total N Mean ± SEM Variance (minutes) (minutes) l. LS LORR 19 5.7 ± 0.3 1.8

2. SS LORR 16 3.5 ± 0.2 0.88

3. ILS LORR 19 7.4 ± 0.4 2.7

4. ISS LORR 37 3.8 ± 0.2 2.2

5. Fl. ILS x ISS LORR 17 6.5 ± 0.5 3.8

6. Fl, ISS x ILS LORR 8 5.3 ± 0.7 3.4

7. F| combined LORR 25 6.1 ± 0.4 3.7

F₂ ILS/ISS x ILS/ISS LORR

8. pigmented 32 6.7 ± 0.5 9.6

9. albino 18 6.1 ± 0.6 6.7

F₂ ILS/ISS x ILS/ISS LORR

10. pigmented 35 6.8 ± 0.4 7.0

11. albino 8 4.3 ± 0.8 5.3

F₂ ISS/ILS x ILS/ISS LORR

12. pigmented 36 6.7 ± 0.3 2.9

13. albino 18 6.2 ± 0.7 8.0

F₂ ISS/ILS x ISS/ILS LORR

14. pigmented 32 7.1 ± 0.6 9.8

15. albino 15 5.7± 0.6 4.6

F₂ A11 LORR 194 6.5 ± 0.2 6.9

16. pigmented 135 6.8 ± 0.2 7.1

17. albino 59 5.8 ± 0.3 6.5

18. N₂ ILS x ILS/ISS LORR 27 6.6 ± 0.4 4.9

19. N₂ ISS/ILS x ILS LORR 28 6.0 ± 0.5 6.1

N₂ ISS x ILS/ISS

20. pigmented LORR 19 6.2 ± 0.6 7.8

21. albino LORR 6 5.2 ± 0.6 2.2

22. total LORR 25 6.0 ± 0.5 6.5

N₂ ILS/ISS x ISS

23. pigmented LORR 15 7.6 ± 0.6 4.7

24. albino LORR 14 6.7 ± 0.5 3.2

25. total LORR 29 7.1 ± 0.4 4.1

(μg/g brain)

LS BLA 11 8.2 ± 0.2 0.81

SS BLA 10 16.1 ± 0.6 5.8

due to genetic effects. Falconer (1981). We have estimated these heritabilities for differential sensitivity to propofol using two distinct approaches. First, an estimate of broad-sense heritability (h²) can be obtained by assessing the variation in length of LORR after propofol injection in the inbred parental strains (ILS and ISS) and in the F₂ reciprocal cross (Table 2). An F2 population derived from an ILS by ISS and the reciprocal intercross had a mean not different from the Fj. Comparing the F₂ variance with the average variance of the Fi and the two parental strains we derived an estimate of broad-sense heritability of 55%. Falconer (1981). A second estimate can be obtained by dividing 1/2 the variance among the 24 RI strain means by 1/2 the inter-strain variance plus the variance within the 24 RIs. Falconer (1981). Using this method, which estimates narrow-sense heritability, we found that about 32% of the variance is genetic. Broad-sense heritability includes estimates of dominance and interactions among loci while narrow-sense heritability only estimates additive effects; these results thus suggest that there may be a substantial genetic component resulting from epistatic (between different genes) interactions, but both methods suggest a large overall genetic component. An estimate of BLA heritability could not be obtained because of an inability to collect BLA on individual mice due to the limited sensitivity of the assay. Location of a QTLfor Propofol Sensitivity The LS and SS selected lines are almost completely differentiated at the albino locus (Tyr) with all SS mice being albino and most of the LS mice being pigmented. Surprisingly, when we examined the LSXSS RIs we found that the eleven albino RI strains averaged significantly shorter LORRs in response to propofol than did the 13 pigmented RI strains (p < .0002), with no difference between males and females as shown in Fig. 4A. The difference in LORR between males and females was not significant; whereas, the LORR difference between pigmented (black bars, 4.8 ± SEM) and albino RI strains (white bars, 9.3 SEM) was highly significant for both males and females (p << 0.0001 , Student's t test two-tailed significance), "n" refers to the number of RI strains. The LORR for each strain was determined from the mean of 5-15 animals of each sex, and the BLA for each strain was determined from the mean of at least 3 animals. The difference in propofol BLA between pigmented (8.4 ± 1.2 μg/gm) and albino (17.2 ± 1.9 μg/gm) strains is highly significant (p « 0.0001, Student's t test two-tailed significance). The pigmented RI strains (black bars) used for propofol BLA determination were 2, 3, 6, 7, 8, 9, 17, 30 and 36; and the albino RI strains (white bars) used were 4, 10, 18, 20, 23, 25, and 33. Male and female data are combined for propofol BLA. The correlation between propofol BLA and LORR for the 16 RI strains for which both measures could be obtained was -0.85 (p < 0.001). RI 32 was excluded from this analysis because it was still segregating for the albino mutation. The albino strains also had very significantly higher BLA (p « .0001; Fig 1A), suggesting the difference in LORR is due to differential CNS sensitivity and not pharmacokinetic differences. The correlation coefficient between BLA and LORR was 0.85 and highly significant (p < 0.001). The LORRs of the albino strains were non-overlapping with the LORRs of the pigmented strains, demonstrating a major effect of a QTL linked to or at the

Tyr locus.

This QTL was mapped using the regression approach described by Haley and Knott, which we previously used in mapping QTLs for alcohol sensitivity. We assessed the genotypes of seven additional SSLP markers spanning 50 centiMorgan (cM) of chromosome 7, obtaining LOD scores of 19 and 21 for males and females, respectively.

The combined LOD score for males and females was about 28 (Fig. 5). far exceeding the value of 3.3 recommended by Lander and Kruglyak for significant linkage in a whole- genome scan. This assignment was highly specific and positioned the QTL to within 2.5 cM of Tyr with 2-LOD support, indicating the probability of the QTL being within this region is greater than 0.99. The peak LOD score was at the Tyr gene itself. This QTL, which we have called Lorpl (Loss Of Righting due to Propofol), explained about 80% of the genetic variance between LS-like and SS-like RI strains, indicating this is the major gene specifying differential propofol sensitivity between LS and SS. BLA also mapped to this region, peaking at the Tyr locus, although with significantly reduced LOD score, not passing the suggested level of 3.4 needed to assure that the QTL is real. With respect to

Fig. 7, ISS mice have the classical albino mutation, whereas the c^2j albino mutation arose spontaneously in C57BL/6 at Jackson Laboratory. Therefore, Fi mice are identical at all loci except the albino locus, pigmented mice (black bars) are c/C and albino mice (white bars) are c/c^2j . LORRs of females are significantly shorter than those of males by 1.3 minutes (p = 0.002, ANOVA two-tailed significance). However, LORRs of albinos are not significantly shorter than those of pigmented mice (p - 0.35, ANOVA one-tailed significance).

Confirmation of Linkage

Although confirmation of linkage after such an astronomical LOD score is not needed, the map location of Lorpl was confirmed independently using a panel of 164 F₂ mice derived from intercrosses of ILS and ISS. These F₂s were genotyped with 16 SSLP markers from murine chromosome 7 that included all of the informative SSLP markers flanking Tyr for about 10 cM (WI/MIT CGR map and Rikke et al., submitted). A peak LOD score of 3.9 was obtained between markers D7MU31, which is within Tyr, and D7MU123, which is less than 2 cM distal to Tyr (Fig 6). We found that F₂ homozygotes for the SS allele of D7MU123, slept 5.7 minutes (SEM = 0.3), heterozygotes slept 6.5 minutes (SEM = 0.3), and LS homozygotes slept 8.0 minutes (SEM = 0.4). The 2.3 minute difference in propofol-induced LORR between mice homozygous for the S allele at D7MU123 and those homozygous for the L allele was consistent with the 2.2 minute difference previously observed between LS and SS, suggesting that all of the genetic difference between LS and SS for propofol sensitivity has been captured in the ILS and ISS strains and that most or all of the genetic difference resides in Lorpl.

Location of a QTL for Ethanol, Enflurane, Isoflurane and Etomidate The QTL location experiments described above were repeated for CNS depressants ethanol (4.1 g/kg), isoflurane (2.0 g/kg), enflurane (5.0 g/kg) and etomidate (20 mg/kg).

The behavioral measure of sensitivity was LORR (as was used in the propofol studies, above). The results (including those for propofol) are shown in Figs. 8-10. The peak LOD scores are at or very close to Tyr for each CNS depressant, just was with propofol. However, the 2-LOD support interval for each is much broader than 2.5 cM as reported for propofol (on the order of 25-30 cM). The results indicate that the genetic locus associated with differential CNS sensitivity is linked to the Tyr locus.

Example 3: A 250 kb fragment in yeast artificial chromosome YRT2 confers increased sensitivity to propofol Transgenic mice harboring YAC YRT2 (covering the mouse tyrosinase locus as isolated from a YAC library of C3H mouse DNA) were kindly provided by Schiitz. Schedl et al. (1993) Nature 362:258-261. YRT2, the resulting 250 kb construct, contains 80 kb of the tyrosinase coding region (Ruppert, S. et al. EMBO J. 7:2715-2722, (1988)), 155 kb of upstream sequences and 15 kb of vector DNA (Fig. 11). The transgenic mice were originally created in outbred albino mouse strain NMRI.

These mice were crossed with albino ISS strain. Progeny from crossing two different strains were denoted FiS. Thus, FiS mice were 50% NMRI and 50% ISS. The FiS mice were then backcrossed with ISS, and these progeny were denoted N₂S (which were 25%) NMRI and 75% ISS). For both FiS and N₂S, mice having the transgene were pigmented, whereas non-transgenic littermates were albinos.

We tested three different YRT2 lines for these experiments. Transgenes insert at random sites in the genome; therefore, it was presumed that each line had its transgenic insert at a different site. Transgenes also tend to integrate as tandemly repeated copies of the original transgenic insert. Schedl et al. determined that one of the transgenic lines had one copy of the transgenic region (denoted Tgl), another line had two copies (Tg2), and another line had eight copies (Tg8). More copies of the transgene generally implies greater expression levels of the transgene, which could explain the greater different seen with the

Tg8 mice. However, expression levels may also depend on where in the genome the DNA has inserted.

Sleep times of transgenic mice were compared to sleep times of non-transgenic littermates. All mice (60 to 90 days old) received 20 mg/kg propofol The results are shown in Fig. 12. N indicates the number of mice tested. For each comparison, the difference was statistically significant. The transgenic mice showed longer sleep time (i.e., increased sensitivity) than non-transgenic mice. In the first group, transgenic mice slept an average of 0.7 minutes longer than non-transgenic mice (p= 0.01). In the second group, transgenic mice slept an average of 0.6 minutes longer than non-transgenic mice (p=0.056). In the third group, transgenic mice slept an average of 1.5 minutes longer than non- transgenic mice (p=0.03). Sleep-time sensitivity was independent of transgene insertion site, indicating that the locus Lorpl is within ihe transgenic region, i.e., within the 250 kb YAC insert.

Example 4: Analysis of sequences on YRT2, including niGIuRS sequences

We analyzed sequences contained in YRT2 in an effort to determine which sequences of the 250 kb insert may be particularly associated with differential CNS depressant activity. To accomplish this, we first isolated a BAC clone as follows. A mouse BAC genomic library was obtained from a commercial source (Research Genetics).

The library was screened by PCR using primer pairs corresponding to known genetic markers that were known to reside on the 250 kb insert of YRT2. A positive BAC clone was identified.. To convert the BAC into a small insert sequence-ready library, we followed the scheme depicted in Fig. 13. BAC DNA was sheared using a sonicator and fragments of about 1.5 kb were size selected on agarose gels and isolated. The size- selected fragments were blunt end ligated into a pBLUESCRIPT™ vector which had been Smal linearized and dephosphorylated. The ligated vectors containing the size-selected fragments were electroporated into XL1-BLUE™ electrocompetent cells. Blue colonies were picked, and the inserts sequenced using fluorescence (Applied Biosystems AB1373A).

Once a sequence had been obtained, it was compared to sequences in GenBank using a BLAST searches. The comparison revealed that some sequences were homologous to human and rat mGluR5, with rat mGluR5 exhibiting the highest homology (SEQ ID NOS:5 and 6). A more extensive sequence of the mGluR5 gene was obtained by sequencing this region using DNA amplified from total brain cDNA from LS and SS mice. The polynucleotide sequence of a coding region of mouse mGluR5 is shown in SEQ ID NO: 1. A polypeptide sequence for mouse mGluR5 is shown in SEQ ID NO:2. A comparison of over 90% of the amino acid sequence for mGluR5 in LS and SS mice showed no differences in either the amino acid or polynucleotide sequences.

Example 5: Glutamate receptor modulation affects propofol sensitivity

LS and SS mice receiving propofol and agonist ACPD LS and SS mice were tested for the effect of ACPD, a group I metabotropic agonist, on propofol sleep time. Five LS (sensitive) mice (60 to 90 days old) and three SS (resistant) mice (60 to 90 days old) were used for this experiment. Intracerebroventricular catheters were implanted under pentobarbital (PB, 80 mg/kg) chloral hydrate (CH, 120 mg/kg) anesthesia, administered by intraperitoneal injection. After a 3 day recovery, propofol was administered at 20 mg/kg by retroorbital sinus injection. 5 μl of agonist ACPD (Tocris-

Cookson) was administered into the lateral ventricles via the implanted catheter. After 30 minutes, the propofol sleep time was assessed. Three LS and three SS control mice received 5 μl saline instead of agonist. Sleep time, measured as LORR, was recorded for test mice and controls. After sleep times were measured, the mice were sacrificed and the brains dissected to confirm the proper placement of the ventricular catheter. In all animals, the catheter was in proper position. The results are tabulated in Table 4. SS (resistant) mice receiving agonist displayed a greater degree of increased resistance (when compared to SS controls) than LS (sensitive) mice receiving agonist. SS mice slept an average of 2.70 minutes shorter with agonist than without agonist, while LS mice slept an average of 0.67 minutes shorter with agonist than without agonist. These results are consistent with the hypothesis that the mGluR system (particularly those in Class I) is more sensitive to stimulation by agonist in SS (resistant) mice than LS mice, and thus may at least partially account for the difference in responsiveness between LS and SS mice. Transgenic mice receiving agonist Transgenic mice as described in Example 3 received approximately 40 μl propofol (20 mg/ml) and 5 μl agonist ACPD (62.5 pmol/5 μl). Sleep times were measured as described. The results are shown in Table 3. Transgenic mice slept an average of 3.97 minutes, while control (non-transgenic littermates) mice slept an average of 0.83 minutes. The average (mean) difference was 3.14 minutes, with a p value of 0.028523.

Example 6: Screening Using YRT2 Sequences

The following example describes cell-based and in vivo screening assays which use mGluR5 polynucleotide sequences found within the YRT2 sequence, but any analogous sequences (e.g., transcriptional control regions, polypeptide-encoding sequences) found within the YRT2 sequence may also be used in the following screens and assays. In an example to identify such agents, an mGluR5-green fluorescent protein (GFP) hybrid gene is assembled in which the expression of GFP is under the control of the mGluR5 transcriptional control region and this hybrid gene is stably introduced into a mammalian cell line (e.g., CHO cells or a cell line with neuronal characteristics).

To screen for agents that modulate the expression of the mGluR5 gene (and may thus effect CNS depressant activity), cells that carry the mGluR5-GFP hybrid gene are grown in standard media and an agent to be tested is added (control cells receive no agent). After a suitable time, the cell suspensions are checked for GFP fluorescence. These assays may be rapidly and conveniently performed in microtiter plates, using a small amount of media and agent to be tested in each well with the cells. Agents are identified by their ability to increase or decrease the amount of GFP fluorescence relative to that of the control cells. A relative increase in GFP fluoresence in cells grown in the presence of the agent may indicate an activation of expression driven from the mGluR5 regulatory elements by the agent. A relative decrease in GFP fluoresence in cells grown in the presence of the agent may indicate a suppression of expression from said regulatory elements. This mGluR5-GFP hybrid gene assay is performed in the presence of a CNS depressant to screen for agents which may modulate the depressant activity on mGluR5 expression, if any.

In another example to identify agents which exhibit CNS depressant activity or which modulate the activity of a CNS depressant, sequences encoding an mGluR5 polypeptide are expressed in cells (e.g., CHO cells or a neuronal cell line) under control of a promoter active in the particular cell type chosen. The promoter may be the endogenous mGluR5 promoter or a heterologous (including an inducible) promoter.

To screen for agents that modulate the activity of the mGluR5 polypeptide (and may thus effect CNS depressant activity), cells that express the mGluR5 polypeptide are grown in appropriate media and an agent to be tested is added (control cells receive no agent). After a suitable time, mGluR5 activity in the cells is measured through, for example, the determination of intracellular calcium release (using, for example, a fluorescent calcium indicator such as fura-2). Agents are identified by their ability to increase or decrease the activity of mGluR5 relative to that in the control cells. This mGluR5 activity assay is performed in the presence of a CNS depressant to screen for agents which may modulate the activity of the depressant on mGluR5 activity, if any. After the identification of agents using cells in culture, the agents are tested in vivo for their effect on CNS depressant activity. Transgenic mice harboring the YRT2 sequences allow the agents to be tested in the context of the CNS and allow the use of assays for CNS depressant sensitivity as described above (e.g., LORR). The transgenic mice for this assay could be those as described in Example 3. As indicated in Example 3, the CNS depressant sensitivity of the transgenic mice appears to be of an intermediate level between that of SS mice and that of LS mice at which an agent can be tested for its ability to increase or decrease the CNS depressant sensitivity. Control over the heterozygosity or the copy number of transgenic YRT2 sequences may provide an animal with a suitable level of CNS depressant sensitivity of this screen.

The agent is administered to animals with or without a CNS depressant (e.g., propofol). Determination of the CNS depressant activity of the agent is made using the standard LORR assessment protocols described in previous Examples.

Although the foregoing invention has been described in some detail by way of illustration and example for purposes of clarity and understanding, it will be apparent to those skilled in the art that certain changes and modifications can be practiced. Therefore, the description and examples should not be construed as limiting the scope of the invention, which is delineated by the appended claims.

Table 3: Sleep times of transgenic receiving mGluR agonist and propofol

DOB = Date of Birth

DOI = Date of Injection

ΓΠ S = Surgery r PB = Pentobarbitol concentration of solution is 8 mg/ml

CH = Chloral Hydrate concentration of solution is 12 mg/ml

ST = Sleep Time, Time Up - Time Out (min)

Δt¹ = number of days in between surgery and propofol inj.

Agonist = ACPD 62.5 pmol/5μl

Prop = Propofol, concentration 20 mg/ml

Δt² = number of minutes in between agonist inj and prop inj

CFO = Cannula Fell out of Skull

Table 4

LS and SS mice given Propofol and Agonist

Line Cage DOB Mou weight DOI Inj PB Inj CH DOI Weight Age Δt' Agonist T Inj Δt² T out/ T Up ST brain Hit for S for ST Ag Pr ln Vial ICV

LS F LS 62-3A 1 7270 IF 20 5 7326 021 0 21 7329 192 59 3 5μl ACPD 0 33 33 39 75 6 75 1 Y

ACPD LS 62-5B 1 7270 2F 20 2 7326 02 02 7329 18 7 59 3 5μl ACPD 3 67 31 58 35 25 40 5 5 25 2 Y

LSP 2 7270 IF 17 7 7326 0 18 0 18 7329 17 5 59 3 5μl ACPD 6 25 31 33 37 58 41 58 4 4 Y

LSP 2 7270 3F 17 1 7326 0 17 0 17 7329 17 3 59 3 5μl ACPD 11 30 25 41 25 44 83 3 58 5 Y

LS M LSP 3 7270 1M 25 0 7326 0 25 0 25 7329 24 8 59 3 5μl ACPD 14 83 29 5 44 33 48 33 4 7 Y

ACPD MEAN= = 4.72

P-Value^» 0.239003

LS F LS-62-5B 1 7270 3F 18 5 7326 0 19 0 19 7329 17 8 59 3 5μl saline 0 31 25 31 25 37 75 6 5 3 Y

CO Saline c: LSP 2 7270 4F 18 6 7326 0 19 0 19 7329 17 5 59 3 Sμl saline 4 5 49 75 54 25 58 67 4 42 6 Y

CD LS M LSP 3 7270 2M 23 6 7326 0 24 0 24 7329 23 4 59 3 5μl saline 8 33 34 42 42 75 48 5 25 6 Y

CO Saline 1 MEAN= = 5.39

Δ Mean = 0.67

SS F SS 62-1B 4 7268 2F 13 7 7326 m 0 14 0 14 7329 13 6 61 3 5μl ACPD 20 35 25 55 25 NS 0 10 Y

ACPD SS-62-4A 5 7268 IF 14 2 7326 0 14 0 14 7329 14 6 61 3 5μl ACPD 23 17 34 33 57 5 59 5 O 2 9 Y in a SS-62-4A 5 7268 2F 15 3 7326 0 15 0 15 7329 15 5 61 3 5μl ACPD 26 33 35 34 61 67 63 1 33 12 Y m rπ MEAN= = 1.11

P-Value- 0.005142

SS F SS 62- IB 4 7268 3F 163 7326 0 16 0 16 7329 16 4 61 3 Sμl saline 11 35 25 46 25 50 3 75 11 Y

SALINE SS-62-4A 5 7268 3F 14 6 7326 0 15 0 15 7329 144 61 3 5μl saline 14 57 34 25 48 92 52 67 3 75 13 Y

SS-62-4A 5 7268 4F 17 0 7326 0 17 0 17 7329 17 7 61 3 5μl saline 18 83 33 25 52 08 56 3 92 14 Y m MEAN= 3.81 r Δ Mean = 2.70

DOB = Date of Birth

DOI = Date of Injection

S = Surgery

PB = Pentobarbitol concentration of solution is 8 mg/ml (80 mg/kg).

CH = Chloral Hydrate concentration of solution is 12 mg/ml (120 mg/kg)

ST = Sleep Time, Time Up - Time Out (min)

Δt¹ = number of days in between surgery and propofol inj

Agonist = ACPD 100 pmol/5μl

Prop = Propofol, concentration 20 mg/ml

Δt² = number of minutes in between agonist inj and prop inj

CFO = Cannula Fell out of Skull

Claims

CLAIMS What is claimed is:

1. A method of identifying an agent which may exhibit CNS depressant activity, comprising the steps of:

(a) introducing a polynucleotide comprising a mouse polynucleotide sequence associated with CNS depressant sensitivity into a suitable host cell, wherein the mouse polynucleotide sequence corresponds to a polynucleotide sequence of yeast artificial chromosome YRT2;

(b) contacting host cell of step (a) with at least one agent to be tested;

(c) analyzing at least one characteristic associated with expression of the mouse YRT2 polynucleotide, wherein an agent is identified by its ability to modulate expression of the mouse YRT2 polynucleotide.

2. The method of claim 1, wherein the mouse polynucleotide is contained in an mGluR5 gene.

3. The method of claim 2, wherein the mouse polynucleotide is a control region of the mGluR5 gene.

4. A method of classifying a CNS depressant, comprising the steps of:

(a) introducing a polynucleotide comprising a mouse polynucleotide sequence associated with CNS depressant sensitivity into a suitable host cell, wherein the mouse polynucleotide sequence corresponds to a polynucleotide sequence of yeast artificial chromosome YRT2;

(b) contacting host cell of step (a) with at least one agent to be tested;

(c) analyzing at least one characteristic associated with expression of the mouse YRT2 polynucleotide. wherein an agent is identified by its ability to modulate expression of the mouse YRT2 polynucleotide. and wherein a CNS depressant which modulates expression may fall within a class of CNS depressants which displays differential reactivity in LS and SS mice.

5. The method of claim 4, wherein the mouse polynucleotide is contained in mGluR5 gene.

6. The method of claim 6, wherein the mouse polynucleotide is a control region of the mGluR5 gene.

7. A method of identifying an agent which may modulate CNS depressant sensitivity in an individual, said method comprising:

(a) introducing a polynucleotide comprising a mouse polynucleotide sequence associated with CNS depressant sensitivity into a suitable host cell, wherein the mouse polynucleotide sequence corresponds to a polynucleotide sequence of yeast artificial chromosome YRT2;

(b) contacting host cell of (a) with at least one agent to be tested; (c) analyze at least one characteristic associated with expression of the mouse YRT2 polynucleotide, wherein an agent is identified by its ability to modulate expression of the mouse YRT2 polynucleotide.

8. The method of claim 7. wherein the mouse polynucleotide is contained in an mGluR5 gene.

9. The method of claim 8, wherein the mouse polynucleotide is a control region of the mGluR5 gene.

10. A method of identifying an agent which may exhibit CNS depressant activity, comprising the steps of:

(a) introducing a polynucleotide comprising a metabotropic glutamine receptor polynucleotide sequence into a suitable host cell;

(b) contacting host cell of step (a) with at least one agent to be tested;

(c) analyze at least one characteristic associated with expression of the mammalian metabotropic glutamate receptor polynucleotide, wherein an agent is identified by its ability to modulate expression of the mammalian metabotropic glutamate receptor polynucleotide.

11. The method of claim 10, wherein the metabotropic glutamate receptor polynucleotide is mammalian.

12. The method of claim 11, wherein the mammalian metabotropic glutamate receptor polynucleotide is human.

13. The method of claim 11 , wherein the mammalian metabotropic glutamate receptor is mGluR5.

14. The method of claim 11 , wherein the mammalian metabotropic glutamate receptor is mGluRl.

15. A method of classifying a CNS depressant, comprising the steps of:

(a) introducing a polynucleotide comprising a metabotropic glutamate receptor polynucleotide sequence into a suitable host cell;

(b) contacting host cell of step (a) with at least one agent to be tested;

(c) analyzing at least one characteristic associated with expression of the metabotropic glutamate receptor polynucleotide. wherein an agent is identified by its ability to modulate expression of the metabotropic glutamate receptor polynucleotide sequence, and wherein a CNS depressant which modulates the metabotropic glutamate receptor polynucleotide expression may fall within a class of CNS depressants which displays differential reactivity in LS and SS mice.

16. The method of claim 15, wherein the metabotropic glutamate receptor polynucleotide is mammalian.

17. The method of claim 16, wherein the mammalian metabotropic glutamate receptor polynucleotide is human.

18. The method of claim 17, wherein the human metabotropic glutamate receptor is mGluR5.

19. The method of claim 16, wherein the human metabotropic glutamate receptor is mGluRl .

20. An isolated polynucleotide comprising a polynucleotide encoding a mouse mGluR5 polypeptide, wherein the mouse mGluR5 polypeptide is at least about 10 contiguous amino acids of SEQ ID NO: 2 and exhibits mGluR5 activity, and wherein the at least about 10 contiguous amino acids are not depicted within SEQ ID NO:6 or SEQ ID NO:7.

21. An isolated polynucleotide comprising a polynucleotide of at least about 25 contiguous nucleotides of SEQ ID NO:l, wherein the at least about 25 contiguous nucleotides are not depicted in SEQ NO: 3 or SEQ ID NO:5. __

22. An isolated polynucleotide comprising a region of at least about 25 contiguous nucleic acids of SEQ ID NO:l, said region having at least about 97% sequence identity to a sequence in SEQ ID NO: 1.

23. A cloning vector comprising the polynucleotide of claim 20.

24. A cloning vector comprising the polynucleotide of claim 21.

25. A cloning vector comprising the polynucleotide of claim 22.

26. An expression vector comprising the polynucleotide of claim 20.

27. An expression vector comprising the polynucleotide of claim 21.

28. An expression vector comprising the polynucleotide of claim 22.

29. A host cell comprising the polynucleotide of claim 20.

30. A host cell comprising the polynucleotide of claim 21.

31. A host cell comprising the polynucleotide of claim 22.

32. The host cell of claim 29, wherein the host cell is mammalian.

33. The host cell of claim 30, wherein the host cell is mammalian.

34. The host cell of claim 31 , wherein the host cell is mammalian.

35. An isolated polypeptide comprising at least about 5 contiguous amino acids of the sequence of SEQ ID NO:2. and wherein the at least about 5 contiguous amino aicds are not depicted in SEQ ID NO:6 or SEQ ID NO:7.

36. The polypeptide of claim 35, wherein the polypeptide comprises the sequence of SEQ ID NO:2.

37. A purified antibody capable of specifically binding to a polypeptide of claim 35.

38. A monoclonal antibody capable of specifically binding to a polypeptide of claim 35.