WO2002022867A2

WO2002022867A2 - Diagnostic and therapeutic use of a phosphoprotein enriched in astrocytes for alzheimer's disease and related neurodegenerative disorders

Info

Publication number: WO2002022867A2
Application number: PCT/EP2001/010526
Authority: WO
Inventors: Rainer Hipfel; Heinz Von Der Kammer; Ralf Krappa; Johannes Pohlner
Original assignee: Evotec Neurosciences Gmbh
Priority date: 2000-09-13
Filing date: 2001-09-12
Publication date: 2002-03-21
Also published as: AU2002212233A1

Abstract

Based on the differential expression of the gene coding for the phophoprotein enriched in astrocytes PEA-15 in specific brain regions of Alzheimer s disease patients, the present invention provides a method for diagnosing or prognosing Alzheimer s disease or other neurodegenerative diseases in a patient. It further provides a method for determining whether a subject is at increased risk of developing Alzheimer s disease or other related neurodegenerative diseases. Furthermore, this invention provides therapeutic and prophylactic methods for treating or preventing Alzheimer s disease and related neurodegenerative disorders using a gene coding for a phosphoprotein enriched in astrocytes, in particular the gene coding for PEA-15. A method of screening for modulating agents of neurodegenerative diseases is also disclosed.

Description

DIAGNOSTIC AND THERAPEUTIC USE OF A PHOSPHOPROTEIN ENRICHED IN ASTROCYTES FOR ALZHEIMER'S DISEASE AND RELATED NEURODEGENERATIVE DISORDERS

The present invention relates to methods of diagnosing, prognosing and monitoring the progression of neurodegenerative diseases in a subject. Furthermore, methods of therapy control and screening for modulating agents of neurodegenerative diseases are provided. The invention also discloses pharmaceutical compositions, kits and recombinant animal models.

Neurodegenerative diseases, in particular Alzheimer's disease, have a severely debilitating impact on a patient's life. Furthermore, these diseases constitute an enormous health, social, and economic burden. Alzheimer's disease is the most common age-related neurodegenerative condition affecting about 10 % of the population over 65 years of age and up to 45 % over age 85 (for a recent review see Vickers et al., Progress in Neurobiology 2000, 60 : 139-165; the contents of all publications, patents and patent applications referred to and cited in the present invention shall be incorporated by reference in their entirety). Presently, this amounts to an estimated 12 million cases in the US, Europe, and Japan. This situation will inevitably worsen with the demographic increase in the number of old people („aging of the baby boomers,,) in developed countries. The neuropathological hallmarks that occur in the brain of individuals suffering from Alzheimer's disease are senile plaques, composed of amyloid-b protein, and profound cytoskeletal changes coinciding with the appearance of abnormal filamentous structures and the formation of neurofibrillary tangles. AD is a progressive disease that is associated with early deficits in memory formation and ultimately leads to the complete erosion of higher cognitive function. A characteristic feature of the pathogenesis of AD is the selective vulnerability of particular brain regions and subpopulations of nerve cells to the degenerative process. Specifically, the temporal lobe region and the hippocampus are affected early and more severely during the progression of the disease. On the other hand, neurons within the frontal cortex, occipital cortex, and the cerebellum remain largely intact and are protected from neurodegeneration (Terry et al., Annals of Neurology 1981, 10 : 184-192).

Currently, there is no cure for AD, nor is there an effective treatment to halt the progression of AD or even a method to diagnose AD ante- mortem with high probability. Several risk factors have been identified that predispose an individual to develop AD, among them most prominently the epsilon4 allele of apolipoprotein E (ApoE). Although there are rare examples of early-onset AD which have been attributed to genetic defects in the genes for APP, presenilin-1, and presenilin-2, the prevalent form of late-onset sporadic AD is of hitherto unknown etiologic origin. The late onset and complex pathogenesis of neurodegenerative disorders pose a formidable challenge to the development of therapeutic and diagnostic agents. Therefore, it is crucial to expand the pool of potential drug targets and diagnostic markers.

It is an object of the present invention to provide methods, materials, and animal models which are suited inter alia for the diagnosis, identification of compounds useful for therapeutic intervention, and development and monitoring of a treatment of Alzheimer's disease or related neurodegenerative diseases. Based on the unexpected finding of the differential expression of the gene coding for the phosphoprotein enriched in astrocytes PEA-15 in certain brain regions of patients suffering from Alzheimer's disease, the present invention sets out for providing such targets, methods, and materials as laid out in the claims section and described herein. The phosphoprotein enriched in astrocytes PEA-15 (rjhosphoprotein enriched in astrocytes - 15 kDa) was first identified by Araujo et al. (Journal of Biological Chemistry 1993, 268 : 5911-5920; the contents of which are incorporated herein by reference) in an attempt to identify major phosphorylated proteins in mouse astrocytes. Subsequently, the murine PEA-15 gene was cloned from an astrocytic cDNA library by Estelles et al. (Journal of Biological Chemistry 1996, 271 : 14800-14806). The human PEA-15 gene sequence (Genbank Accession No. NM 003768) was assembled from several partially overlapping ESTs (Expressed Sequence lags). The PEA-15 gene codes for a 130-amino acid protein with a predicted molecular mass of 15 kDa which is highly conserved (96% identical in coding sequence) between mouse and human. PEA-15 shares no similarity with any other known proteins. It is widely expressed throughout the body. In brain PEA-15 expression is particularly prominent in astrocytes of the hippocampal region. However, PEA-15 is also expressed in some neurons and in many cultured brain cell types. PEA-15 is a substrate of protein kinase C. It can exist in three molecular forms depending on its different phosphorylation states (Danziger et al., Journal of Neurochemistry 1995, 64: 1016-1025; the contents of which are incorporated herein by reference). The unphosphorylated form of PEA-15 is mainly found in the cytosol, whereas the protein kinase C-phosphorylated form is membrane associated and remains in a fraction that contains stabilized microtubules. PEA-15 expression and phosphorylation levels in the mouse increase during development and reach a maximum during adulthood.

Condorelli et al. (EMBO Journal 1998, 17: 3858-3866) independently identified PEA-15 in a differential display screen of fibroblasts from diabetes patients where it was named PED (p_hosphoprotein enriched in diabetes). PEA-15 expression was elevated in diabetes patients. The authors determined that PEA-15 controls the level of the glucose transporter Glutl on the cell membrane and that overexpression of PEA- 15 impairs insulin-stimulated glucose transport and glucose transporter translocation.

Several studies implicate PEA-15 in the regulation of apoptosis (Condorelli et al., Oncogene 1999, 18 :4409-4415; Kitsberg et al., Journal of Neuroscience 1999, 19 :8244-8251; Estelles et al., Developmental Biology 1999, 216 : 16-28; the contents of which are incorporated herein by reference). The PEA-15 protein consists of an N- terminal death effector domain (DED). This domain plays a critical role in the regulation of apoptosis and mediates the physical interaction of PEA-15 with FADD and caspase-8, molecular components of the death- inducing apoptotic signaling cascade. Very recently (Zhang et al., Journal of Biological Chemistry 2000, electronically published manuscript), the PEA-15 protein was shown to physically interact with phospholipase D, a signal-transducing membrane-associated enzyme implicated in diverse processes including apoptosis and glucose transport.

A relationship between a phosphoprotein enriched in astrocytes and neurodegenerative diseases such as Alzheimer's disease has not been described yet. Such a link offers new ways inter alia for the diagnosis and treatment of these diseases.

The term „and/orⁿ as used in the present specifications and the claims implies that the phrases before and after this term are to be considered either as alternatives or in combination. For instance, the wording determination of a level and/or an activity" means that either only a level, or only an activity, or both a level and an activity are determined. The term „fragment^,λ as used herein is meant to comprise e.g. an alternatively spliced, or truncated, or otherwise cleaved transcription product or translation product. The term „derivative" as used herein refers to a mutant, or an RNA-edited, or a chemically modified, or otherwise altered transcription product, and to a mutant, or chemically modified, or otherwise altered translation product. For instance, a „derivative" may be generated by processes such as altered phosphorylation, or glycosylation, or lipidation, or by altered signal peptide cleavage or other types of maturation cleavage. These processes may occur post-translationally. Fragments and/or derivatives of a phosphoprotein enriched in astrocytes may include, but are not limited to, a functional death effector domain (DED) or other functional modules contained within the polypeptide sequence of a phosphoprotein enriched in astrocytes. The term „level" as used herein is meant to comprise a gage of, or a measure of the amount of, or a concentration of a transcription product, for instance an mRNA, or a translation product. The term „activity" as used herein can be understood as a measure for the ability of a transcription product or a translation product to produce a biological effect or a measure for a level of biologically active molecules. The terms „level ^λ and/or „activity" as used herein further refer to gene expression levels or gene activity. Gene expression can be defined as the utilization of the information contained in a gene by transcription and translation leading to the production of a gene product. A gene product comprises either RNA or protein and is the result of expression of a gene. The amount of a gene product is used to measure how active a gene is.

In one aspect, the invention features a method of diagnosing or prognosing a neurodegenerative disease in a subject, or determining whether a patient is at increased risk of becoming afflicted with said disease. The method comprises: determining a level, or an activity, or both said level and said activity of (i) a transcription product of a gene coding for a phosphoprotein enriched in astrocytes, and/or of (ii) a translation product of a gene coding for a phosphoprotein enriched in astrocytes, and/or of (iii) a fragment or derivative of said transcription or translation product in a sample from said subject and comparing said level, and/or said activity to a reference value representing a known disease or health status, thereby diagnosing or prognosing said neurodegenerative disease in said subject, or determining whether said subject is at increased risk of developing said neurodegenerative disease.

In a further aspect, the invention features a method of monitoring the progression of a neurodegenerative disease in a subject. A level, or an activity, or both said level and said activity, of (i) a transcription product of a gene coding for a phosphoprotein enriched in astrocytes, and/or of (ii) a translation product of a gene coding for a phosphoprotein enriched in astrocytes, and/or of (iii) a fragment or derivative of said transcription or translation product in a sample from said subject is determined. Said level and/or said activity is compared to a reference value representing a known disease or health status. Thereby the progression of said neurodegenerative disease in said subject is monitored.

In still a further aspect, the invention features a method of evaluating a treatment for a neurodegenerative disease, comprising determining a level, or an activity, or both said level and said activity of (i) a transcription product of a gene coding for a phosphoprotein enriched in astrocytes, and/or of (ii) a translation product of a gene coding for a phosphoprotein enriched in astrocytes, and/or of (iii) a fragment or derivative of said transcription or translation product in a sample obtained from a subject being treated for said disease. Said level, or said activity, or both said level and said activity are compared to a reference value representing a known disease or health status, thereby evaluating the treatment for said neurodegenerative disease. In a preferred embodiment, said subjects suffer from Alzheimer's disease. Further examples of neurodegenerative diseases are Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis, Pick's disease, fronto-temporal dementia, progressive nuclear palsy, and corticobasal degeneration. Another condition featuring neurodegenerative processes is stroke.

In the present invention, it is particularly preferred that said phosphoprotein enriched in astrocytes is PEA-15.

It is preferred that the sample to be analyzed and determined is selected from the group comprising brain tissue or other body cells. The sample can also comprise cerebrospinal fluid or other body fluids including saliva, urine, serum plasma, or mucus.

In further preferred embodiments, said reference value is that of a level, or an activity, or both said level and said activity of (i) a transcription product of a gene coding for a phosphoprotein enriched in astrocytes, and/or of (ii) a translation product of a gene coding for a phosphoprotein enriched in astrocytes, and/or of (iii) a fragment or derivative of said transcription or translation product in a sample from a subject not suffering from said neurodegenerative disease.

In preferred embodiments, an altered amount of PEA-15 mRNA and/or PEA-15 protein in a sample from said subject relative to a reference value representing a known health status indicates a diagnosis, or prognosis, or increased risk of becoming diseased with a neurodegenerative disease, particularly Alzheimer's disease.

In preferred embodiments, measurement of the level of transcription products of a gene coding for a phosphoprotein enriched in astrocytes is performed in a sample from a subject using Northern blots with probes specific for said gene. Another preferred method of measuring said level is by quantitative PCR with primer combinations which amplify said gene-specific sequences from cDNA obtained by reverse transcription of RNA extracted from a sample of a subject. These techniques are known to those of ordinary skill in the art (see Sambrook and Russell, Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, New York, 2000).

Furthermore, the level and/or activity of a translation product of said gene and/or fragment or derivative of said translation product can be detected using a Western blot analysis, an immunoassay, an enzyme activity assay, and/or binding assay. These assays can measure the amount of binding between said protein molecule and an anti-protein antibody by the use of enzymatic, chromodynamic, radioactive, or luminescent labels which are attached to either the anti-protein antibody or a secondary antibody which binds the anti-protein antibody. In addition, other high affinity ligands may be used. Immunoassays which can be used include e.g. ELISAs, Western blots and other techniques known to those of ordinary skill in the art (see Harlow and Lane, Antibodies: A Laboratory Manual, Cold Spring Harbor Laboratory Press,

Cold Spring Harbor, New York, 1999).

In a preferred embodiment, the level, or the activity, or both said level and said activity of (i) a transcription product of a gene coding for a phosphoprotein enriched in astrocytes, and/or of (ii) a translation product of a gene coding for a phosphoprotein enriched in astrocytes, and/or of (iii) a fragment or derivative of said transcription or translation product in a series of samples taken from said subject over a period of time is compared, in order to monitor the progression of said disease. In further preferred embodiments, said subject receives a treatment prior to one or more of said sample gatherings. In yet another preferred embodiment, said level and/or activity is determined before and after said treatment of said subject.

In another aspect, the invention features a method of treating or preventing a neurodegenerative disease, in particular Alzheimer's disease, in a subject comprising the administration to said subject in a therapeutically or prophylactically effective amount of an agent or agents which directly or indirectly affect a level, or an activity, or both said level and said activity, of (i) a gene coding for a phosphoprotein enriched in astrocytes, and/or (ii) a transcription product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (iii) a translation product of said gene, and/or (iv) a fragment or derivative of (i) to (iii).

In preferred embodiments, the method comprises the application of per se known methods of gene therapy and/or antisense nucleic acid technology to administer said agent or agents. In general, gene therapy comprises several approaches: molecular replacement of a mutated gene, addition of a new gene resulting in the synthesis of a therapeutic protein, and modulation of endogenous cellular gene expression by recombinant expression methods or by drugs. Gene-transfer techniques are described in detail (see e.g. Behr, Ace Chem Res 1993, 26 : 274-278 and Mulligan, Science, 1993, 260 : 926-931; the contents of which are incorporated herein by reference) and include direct gene-transfer techniques such as mechanical microinjection of DNA into a cell as well as indirect techniques employing biological vectors (like recombinant viruses, especially retroviruses) or model liposomes, or techniques based on transfection with DNA coprecipitation with polycations, cell membrane pertubation by chemical (solvents, detergents, polymers, enzymes) or physical means (mechanic, osmotic, thermic, electric shocks). The postnatal gene transfer into the central nervous system has been described in detail (see e.g. Wolff, Curr Opin Neurobiol 1993, 3 :743-748).

In particular, the invention features a method of treating or preventing a neurodegenerative disease by means of antisense nucleic acid therapy, i.e. the down-regulation of an inappropriately expressed or defective gene by the introduction of antisense nucleic acids or derivatives thereof into certain critical cells (see e.g. Gillespie, DN&P 1992, 5 : 389-395; Agrawal and Akhtar, Trends Biotechnol 1995, 13 : 197-199; Crooke, Biotechnology 1992, 10 :882-6; the contents of which are incorporated herein by reference). Apart from hybridization strategies, the application of ribozymes, i.e. RNA molecules that act as enzymes, destroying RNA that carries the message of disease has also been described (see e.g. Barinaga, Science 1993, 262 : 1512-1514; the contents of which are incorporated herein by reference). In preferred embodiments, the subject to be treated is a human, and therapeutic antisense nucleic acids or derivatives thereof are directed against a human gene for a phosphoprotein enriched in astrocytes, particularly the PEA-15 gene. It is preferred that cells of the central nervous system, preferably the brain, of a subject are treated in such a way. Cell penetration can be performed by known strategies such as coupling of antisense nucleic acids and derivatives thereof to carrier particles, or the above described techniques. Strategies for administering targeted therapeutic oligodeoxynucleotides are known to those of skill in the art (see e.g. Wickstrom, Trends Biotechnol, 1992, 10 : 281-287; the contents of which are incorporated herein by reference). In some cases, delivery can be performed by mere topical application. Further approaches are directed to intracellular expression of antisense RNA. In this strategy, cells are transformed ex vivo with a recombinant gene that directs the synthesis of an RNA that is complementary to a region of target nucleic acid. Therapeutical use of intracellularly expressed antisense RNA is procedurally similar to gene therapy. In further preferred embodiments, the method comprises grafting donor cells into the central nervous system, preferably the brain, of said subject, or donor cells preferably treated so as to minimize or reduce graft rejection, wherein said donor cells are genetically modified by insertion of at least one transgene encoding said agent or agents. Said transgene might be carried by a viral vector, in particular a retroviral vector. The transgene can be inserted into the donor cells by a nonviral physical transfection of DNA encoding a transgene, in particular by microinjection. Insertion of the transgene can also be performed by electroporation, chemically mediated transfection, in particular calcium phosphate transfection, liposomal mediated transfection, etc.

In preferred embodiments, said agent is a therapeutic protein which can be administered to said subject, preferably a human, by a process comprising introducing subject cells into said subject, said subject cells having been treated in vitro to insert a DNA segment encoding said therapeutic protein, said subject cells expressing in vivo in said subject a therapeutically effective amount of said therapeutic protein. Said DNA segment can be inserted into said cells in vitro by a viral vector, in particular a retroviral vector. Said agent, particularly a therapeutic protein, can further be administered to said subject by a process comprising the injection or the systemic administration of a fusion protein, said fusion protein consisting of a fusion of a protein transduction domain with said agent.

In preferred embodiments, the subject can be a human, an experimental animal, e.g. a mammal, a mouse, a rat, a fish, a fly, or a worm; a domestic animal, or a non-human primate. The experimental animal can be an animal model for a neurodegenerative disorder, e.g. a transgenic mouse with an Alzheimer's-type neuropathology. In a further aspect, the invention features a modulator of an activity, or a level, or both said activity and said level of at least one substance which is selected from the group consisting of (i) a gene coding for a phosphoprotein enriched in astrocytes, and/or (ii) a transcription product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (iii) a translation product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (iv) a fragment or derivative of (i) to (iii).

In an additional aspect, the invention features a pharmaceutical composition comprising said modulator and preferably a pharmaceutical carrier. Said carrier refers to a diluent, adjuvant, excipient, or vehicle with which the modulator is administered.

In a further aspect, the invention features a modulator of an activity, or a level, or both said activity and said level of at least one substance which is selected from the group consisting of (i) a gene coding for a phosphoprotein enriched in astrocytes, and/or (ii) a transcription product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (iii) a translation product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (iv) a fragment or derivative of (i) to (iii) for use in a pharmaceutical composition.

In another aspect, the invention provides for the use of a modulator of an activity, or a level, or both said activity and said level of at least one substance which is selected from the group consisting of (i) a gene coding for a phosphoprotein enriched in astrocytes, and/or (ii) a transcription product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (iii) a translation product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (iv) a fragment or derivative of (i) to (iii) for a preparation of a medicament for treating or preventing a neurodegenerative disease, in particular Alzheimer's disease. In one aspect, the present invention also provides a kit comprising one or more containers filled with a therapeutically or prophylactically effective amount of said pharmaceutical composition.

In a further aspect, the invention features a recombinant, non-human animal comprising a non-native gene sequence coding for a phosphoprotein enriched in astrocytes, or a fragment thereof, or a derivative thereof. The generation of said recombinant, non-human animal compπses (i) providing a gene targeting construct containing said gene sequence and a selectable marker sequence, and (ii) introducing said targeting construct into a stem cell of a non-human animal, and (iii) introducing said non-human animal stem cell into a non-human embryo, and (iv) transplanting said embryo into a pseudopregnant non-human animal, and (v) allowing said embryo to develop to term, and (vi) identifying a genetically altered non-human animal whose genome comprises a modification of said gene sequence in both alleles, and (vii) breeding the genetically altered non-human animal of step (vi) to obtain a genetically altered non-human animal whose genome comprises a modification of said endogenous gene, wherein said gene is mis-expressed, or under-expressed, or over-expressed, and wherein said disruption or alteration results in said non-human animal exhibiting a predisposition to developing symptoms of neuropathology similar to a neurodegenerative disease, in particular Alzheimer's disease. Strategies and techniques for the generation and construction of such an animal are known to those of ordinary skill in the art (see e.g. Capecchi, Science, 1989, 244: 1288-1292 and Hogan et al., 1994, Manipulating the Mouse Embryo: A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, New York; the contents of the foregoing are incorporated herein by reference). It is preferred to make use of such a recombinant non-human animal as an animal model for investigating neurodegenerative diseases, in particular Alzheimer's disease.

In preferred embodiments, said recombinant, non-human animal comprises a non-native gene sequence coding for the phosphoprotein enriched in astrocytes PEA-15, or a fragment thereof.

In another aspect, the invention features an assay for screening for a modulator of neurodegenerative diseases, in particular Alzheimer's disease, or related diseases and disorders of one or more substances selected from the group consisting of (i) a gene coding for a phosphoprotein enriched in astrocytes, and/or (ii) a transcription product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (iii) a translation product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (iv) a fragment or derivative of (i) to (iii). This screening method comprises (a) contacting a cell with a test compound, and (b) measuring the level, or the activity, or both the level and the activity of one or more substances recited in (i) to (iv), and (c) measuring the level, or the activity, or both the level and the activity of said substances in a control cell not contacted with said test compound, and (d) comparing the levels of the substance in the cells of step (b) and (c), wherein an alteration in the level and/or activity of said substances in the contacted cells indicates that the test compound is a modulator of said diseases and disorders.

In one further aspect, the invention features a screening assay for a modulator of neurodegenerative diseases, in particular Alzheimer's disease, or related diseases and disorders of one or more substances selected from the group consisting of (i) a gene coding for a phosphoprotein enriched in astrocytes, and/or (ii) a transcription product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (iii) a translation product of a gene coding for a phosphoprotein, and/or (iv) a fragment or derivative of (i) to (iii), comprising (a) administering a test compound to a test animal which is predisposed to developing or has already developed a neurodegenerative disease or related diseases or disorders, and (b) measuring the level and/or activity of one or more substances recited in (i) to (iv), and (c) measuring the level and/or activity of said substances in a matched control animal which is equally predisposed to developing or has already developed said diseases and to which animal no such test compound has been administered, and (d) comparing the level and/or activity of the substance in the animals of step (b) and (c), wherein an alteration in the level and/or activity of substances in the test animal indicates that the test compound is a modulator of said diseases and disorders.

In another embodiment, the present invention provides a method for producing a medicament comprising the steps of (i) identifying a modulator of neurodegenerative diseases by a method of the aforementioned screening assays and (ii) admixing the modulator with a pharmaceutical carrier. Said modulator may also be identifiable by other assays of screening.

In a preferred embodiment, said test animal and/or said control animal is a recombinant, non-human animal which expresses a gene for a phosphoprotein enriched in astrocytes, or a fragment thereof, or a derivative thereof, under the control of a transcriptional regulatory element which is not the native transcriptional control regulatory element of said gene for a phosphoprotein enriched in astrocytes.

In another aspect, the present invention provides for a method of testing a compound, preferably an assay for screening a plurality of compounds, for inhibition of binding between a ligand and a phosphoprotein enriched in astrocytes, or a fragment or derivative thereof. Said method comprises the steps of (i) adding a liquid suspension of said phosphoprotein enriched in astrocytes, or a fragment or derivative thereof, to a plurality of containers, and (ii) adding a compound, preferably a plurality of compounds, to be screened for said inhibition to said plurality of containers, and (iii) adding detectable ligand, preferably fluorescently detectable ligand, to said containers, and (iv) incubating the liquid suspension of said phosphoprotein enriched in astrocytes, or said fragment or derivative thereof, and said compounds, and said detectable ligand, and (v) measuring the amounts of detectable ligand or fluorescence associated with said phosphoprotein enriched in astrocytes, or with said fragment or derivative thereof, and (vi) determining the degree of inhibition by one or more of said compounds of binding of said ligand to said phosphoprotein enriched in astrocytes, or said fragment or derivative thereof. Instead of utilizing a fluorescently detectable label, it might in some aspects be preferred to use any other detectable label known to the person skilled in the art, e.g. radioactive label, and detect it accordingly. Said method may be useful for the identification of novel compounds as well as for evaluating compounds which have been improved or otherwise optimized in their ability to inhibit the binding of a ligand to a phosphoprotein enriched in astrocytes, or a fragment or derivative thereof.

In one further embodiment, the present invention provides a method for producing a medicament comprising the steps of (i) identifying a compound as an inhibitor by the aforementioned method of inhibitory binding assay and (ii) admixing the compound with a pharmaceutical carrier. Said compound may also be identifiable by other assays of screening.

In one further aspect, the invention features a method of testing a compound, preferably an assay for screening a plurality of compounds, to determine the degree of binding of said compound or compounds to a phosphoprotein enriched in astrocytes, or to a fragment or derivative thereof. Said method comprises the steps of (i) adding a liquid suspension of said phosphoprotein enriched in astrocytes, or a fragment or derivative thereof, to a plurality of containers, and (ii) adding a detectable compound, preferably a plurality of detectable compounds, in particular fluorescently detectable compounds, to be screened for said binding to said plurality of containers, and (iii) incubating the liquid suspension of said phosphoprotein enriched in astrocytes, or said fragment or derivative thereof, and said detectable compound, preferably said plurality of detectable compounds, and (iv) measuring the amounts of detectable compound or fluorescence associated with said phosphoprotein enriched in astrocytes, or with said fragment or derivative thereof, and (v) determining the degree of binding by one or more of said compounds to said phosphoprotein enriched in astrocytes, or said fragment or derivative thereof. In this type of assay it might be preferred to use a fluorescent label. However, any other type of detectable label might also be employed. Said method may be useful for the identification of novel compounds as well as for evaluating compounds which have been improved or otherwise optimized in their ability to bind to a phosphoprotein enriched in astrocytes.

In one further embodiment, the present invention provides a method for producing a medicament comprising the steps of (i) identifying a compound as a binder to a phosphoprotein enriched in astrocytes by the aforementioned method of binding assays and (ii) admixing the compound with a pharmaceutical carrier. Said compound may also be identifiable by other assays of screening.

In another embodiment, the present invention provides for a medicament obtainable by any of the methods according to the herein claimed screening assays. In one further embodiment, the instant invention provides for a medicament obtained by any of the methods according to the herein claimed screening assays.

In all types of assays disclosed herein it is preferred to study and conduct screening assays with the phosphoprotein PEA-15.

Other features and advantages of the invention will be apparent from the following description of figures and examples.

Figure 1 depicts the brain regions with selective vulnerability to neuronal loss and degeneration in Alzheimer's disease. Primarily neurons within the inferior temporal lobe, the entorhinal cortex, the hippocampus, and the amygdala degenerate in Alzheimer's disease (Terry et al., Annals of Neurology 1981, 10 : 184-192). These brain regions are mostly involved in the processing of learning and memory functions. In contrast, neurons within the frontal cortex, the occipital cortex, and the cerebellum are largely intact and preserved from the neurodegenerative processes in Alzheimer's disease. Brain tissues from the frontal cortex (F) and the temporal cortex (T) of Alzheimer's disease patients and ' healthy, age-matched control individuals were used for the herein disclosed examples. For illustrative purposes, the image of a healthy brain was taken from a publication by Strange PG (1992, Brain Biochem. Brain Disord.).

Figure 2 discloses the initial identification by differential expression of PEA-15 in a suppressive subtractive hybridization screen. The figure shows a clipping of a large-scale dot blot hybridization experiment. Individual cDNA clones from a temporally subtracted library were arrayed onto a nylon membrane and hybridized with probes enriched for genes expressed in the frontal cortex (F) and the temporal cortex (T) from an Alzheimer's disease patient. Note the significant increase in intensity of the hybridization signal for PEA-15 (see arrows) in the lower left corner of panel (T) as compared to panel (F).

Figure 3 illustrates the verification of the differential expression of PEA- 15 by quantitative RT-PCR analysis. Quantification of RT-PCR products from RNA samples collected from the frontal cortex (F) and temporal cortex (T) of healthy, age-matched control individuals (Fig 3a) and Alzheimer's disease patients (Fig 3b) was performed by the LightCycler™ rapid thermal cycling technique. The data were normalized to cyclophilin B which showed no significant difference in its gene expression level in the two analyzed brain tissues. The figure shows the kinetics of amplification by plotting the cycle number against the amount of amplified material as measured by its fluorescence. The amplification kinetics of PEA-15 cDNA from both the frontal and temporal cortices of a normal control individual during the exponential phase of the reaction overlap, whereas in Alzheimer's disease (Fig 3b) there is a significant shift of the curve for the sample from temporal cortex, indicating an up- regulation of PEA-15 mRNA in the temporal cortex in comparison to the frontal cortex.

Table 1 lists the level of transcriptional up-regulation of the PEA-15 gene in the temporal cortex relative to the frontal cortex for two Alzheimer's disease patients and two healthy, age-matched control individuals.

EXAMPLE I

(i) Brain tissue dissection from patients with Alzheimer's disease: Brain tissues from Alzheimer's disease patients and age-matched control subjects were obtained from qualified institutions and brain banks. The tissue was collected within a few hours of death and immediately frozen on dry ice. Sample sections from each tissue were fixed in paraformaldehyde, and histopathological confirmation of the diagnosis was performed by said qualified institutions and brain banks. Brain areas for differential expression analysis were selected (see Fig. 1) and stored at -80 °C until RNA extractions were performed.

(ii) Isolation of total mRNA: Total RNA was extracted from post-mortem brain tissue by using the RNeasy™ kit (Qiagen) according to the manufacturer's protocol. The quality of the prepared RNA was determined by formaldehyde agarose gel electrophoresis and Northern blotting according to standard procedures (Sambrook and Russell, Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, New York, 2000). The mRNA was isolated from the total RNA preparation using the Quickprep Micro™ mRNA Purification Kit (Pharmacia Biotech) with yields between 1 and 5 %.

(iii) cDNA synthesis and identification of differentially expressed genes by suppressive subtractive hybridization : This technique compares two populations of mRNA and provides clones of genes that are expressed in one population but not in the other. The applied technique was described in detail by Diatchenko et al. (Proc Natl Acad Sci USA 1996, 93 : 6025-30). In the present invention, mRNA populations from postmortem brain tissues from Alzheimer's disease patients were compared. Specifically, mRNA of the frontal cortex was subtracted from mRNA of the inferior temporal cortex. The necessary reagents were taken from the PCR-Select™ cDNA subtraction kit (Clontech), and all steps were performed as described in the manufacturer's protocol. Specifically, 2μg mRNA each were used for first-strand and second-strand cDNA synthesis. After Rsal-digestion and adaptor ligation hybridization of tester and driver was performed for 8 hours (first hybridization) and 15 hours (second hybridization) at 68 °C. Two PCR steps were performed to amplify differentially expressed genes (first PCR: 27 cycles of 94 °C and 30 sec, 66 °C and 30 sec, and 72 °C and 1.5 min; nested PCR: 12 cycles of 94 °C and 30 sec, 66 °C and 30 sec, and 72 °C and 1.5 min) using adaptor specific primers (included in the subtraction kit) and 50x Advantage Polymerase Mix (Clontech). Efficiencies of Rsal-digestions, adaptor ligations and subtractive hybridizations were checked as recommended in the kit. Subtracted cDNAs were inserted into the pCR® vector and transformed into E.coli INVaF ' cells (Invitrogen). To isolate individual cDNAs of the subtracted library single bacterial transformants were incubated in 100 μl LB (with 50 μg/ml ampicillin) at 37 °C for at least 4 hours. Inserts were PCR amplified (95 °C and 30 sec, 68 °C and 3 min for 30 cycles) in a volume of 20 μl containing 10 mM Tris-HCI pH 9.0, 1.5 mM MgCI₂, 50 mM KCI, 200 μM dNTP, 0.5 μM adaptor specific primers (included in the subtraction kit), 1.5 Units Taq polymerase (Pharmacia Biotech), and lμl of bacterial culture. An aliquot of the mixture (1.5 μl) containing 3 μl PCR amplified inserts and 2 μl 0.3 N NaOH/15% Ficoll were spotted onto a positively charged nylon membrane (Roche). In this way, hundreds of spots were arrayed on duplicate filters for subsequent hybridization. The differential screening step consisted of hybridizations of the subtracted library with itself to minimize background (Wang and Brown, Proc Natl Acad Sci USA 1991, 88 : 11505-9). The probes were made of the nested PCR product of the subtraction following the instructions of the Clontech subtraction kit. Labeling with digoxigenin was performed with the DIG DNA Labeling Kit (Roche). Hybridizations were carried out overnight in DIG Easy HYB (Roche) at 43 °C. The filters were washed twice in 2 x SSC / 0.5 % SDS at 68 °C for 15 min and twice in 0.1 x SSC / 0.5 % SDS at 68 °C for 15 min, and subjected to detection using anti-DIG-AP conjugates and CDP- Star™ as chemiluminescent substrate according to the instructions of the DIG DNA Detection Kit (Roche). Blots were exposed to Kodak Biomax MR chemiluminescent film at room temperature for several minutes. The nucleotide sequences of clones of interest were obtained using methods well known to those skilled in the art. For nucleotide sequence analysis and homology searches, computer algorithms of the University of Wisconsin Genetics Computer Group (GCG) in conjunction with publicly available nucleotide and protein sequence information (Genbank and EMBL databases) were employed.

(iv) Confirmation of differential expression by quantitative RT-PCR: Positive corroboration of differential expression of the PEA-15 gene was performed using the LightCycler™ technology (Roche). This technique features rapid thermal cyling for the polymerase chain reaction as well as real-time measurement of fluorescent signals during amplification and therefore allows for highly accurate quantification of RT-PCR products by using a kinetic rather than an endpoint approach. The ratio of PEA-15 cDNA from the temporal cortex versus frontal cortex was determined (relative quantification). In a first step, a standard curve was generated to determine the efficiency of the PCR with specific primers for PEA-15 (5'-CCATCTATAGGGTCCCAACTTGG-3' and 5'-GGCTTGGGATGTTCTTCACC- 3'). PCR amplification (95 °C and 1 sec, 56 °C and 5 sec, and 72 °C and 5 sec) was performed in a volume of 20 μl containing Lightcycler-DNA Master SYBR Green ready-to-use mix (contains Taq DNA polymerase, reaction buffer, dNTP mix with dUTP instead of dTTP, SYBR Green I dye, and 1 mM MgCI₂; Roche), additional 3 mM MgCI₂, 0,5 μM primers, 0,16 μl TaqStart® antibody (Clontech), and 1 μl of a cDNA dilution series (40, 20, 10, 5, and 1 ng human total brain cDNA, Clontech). Melting curve analysis revealed a single peak at approximately 83°C with no visible primer dimers. Agarose gel analysis of the PCR product showed one single band of the expected size (72 bp).

The same protocol was applied to determine the PCR efficiency of the reference gene, cyclophilin B, using the specific primers 5'- ACTGAAGCACTACGGGCCTG-3' and 5'-AGCCGTTGGTGTCTTTGCC-3' except for MgCI₂ (additional 1 mM was added instead of 3 mM). Cyclophilin-B was chosen for normalization because it was found to be the least regulated gene among all analyzed housekeeping genes. Melting curve analysis revealed a single peak at approximately 87 °C with no visible primer dimers. Agarose gel analysis of the PCR product showed one single band of the expected size (62 bp).

The logarithm of the cDNA concentration was plotted against the threshold cycle number C_t for both PEA-15 and cyclophilin B. The slopes and the intercepts of the standard curves (i.e. linear regressions) were calculated for both genes. In a second step, cDNA from temporal cortex and frontal cortex was analyzed in parallel and normalized to cyclophilin B. The C_t values were measured and converted to ng total brain cDNA using the corresponding standard curves:

10 ^Λ ( (C_t value - intercept) / slope ) [ng total brain cDNA]

The values of temporal and frontal cortex PEA-15 cDNAs were normalized to cyclophilin B, and the ratio was calculated using the following formula :

PEA-15 temporal [ng] / cyclophilin B temporal [ng] Ratio = - - -—

PEA-15 frontal [ng] / cyclophilin B frontal [ng]

The results of one such quantitative RT-PCR analysis for the PEA-15 gene are shown in Fig. 3. Table 1 :

SAMPLE A (folcH

patient 1 1.73 patient 2 1.74

control 1 1.03 control 2 1.31

Claims

1. A method of diagnosing or prognosing a neurodegenerative disease in a subject, or determining whether a subject is at increased risk of developing said disease, comprising determining a level and/or an activity of (i) a transcription product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (ii) a translation product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (iii) a fragment or derivative of said transcription or translation product, in a sample from said subject and comparing said level and/or said activity to a reference value representing a known disease or health status, thereby diagnosing or prognosing said neurodegenerative disease in said subject, or determining whether said subject is at increased risk of developing said neurodegenerative disease.

2. A method of monitoring the progression of a neurodegenerative disease in a subject, comprising determining a level and/or an activity of (i) a transcription product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (ii) a translation product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (iii) a fragment or derivative of said transcription or translation product, in a sample from said subject and comparing said level and/or said activity to a reference value representing a known disease or health status, thereby monitoring the progression of said neurodegenerative disease in said subject.

3. A method of evaluating a treatment for a neurodegenerative disease, comprising determining a level and/or an activity of (i) a transcription product of a gene coding for a phosphoprotein enriched in astrocytes, and/or

(ii) a translation product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (iii) a fragment or derivative of said transcription or translation product, in a sample from a subject being treated for said disease and comparing said level and/or said activity to a reference value representing a known disease or health status, thereby evaluating said treatment for said neurodegenerative disease.

4. The method according to any of claims 1 to 3 wherein said neurodegenerative disease is Alzheimer's disease.

5. The method according to any of claims 1 to 4 wherein said phosphoprotein enriched in astrocytes is PEA-15.

6. The method according to any of claims 1 to 5 wherein said sample comprises a cell, or a tissue, or a body fluid, in particular cerebrospinal fluid.

7. The method according to any of claims 1 to 6 wherein said reference value is that of a level and/or an activity of (i) a transcription product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (ii) a translation product of a gene coding for a phosphoprotein enriched in astrocytes, and/or

(iii) a fragment or derivative of said transcription or translation product, in a sample from a subject not suffering from said neurodegenerative disease.

8. The method according to any of claims 1 to 7 wherein an altered amount of PEA-15 mRNA and/or PEA-15 protein in a cell, or tissue, or body fluid, in particular cerebrospinal fluid, from said subject relative to a reference value representing a known health status indicates a diagnosis, or prognosis, or increased risk of Alzheimer's disease in said subject.

9. The method according to any of claims 1 to 8 wherein said transcription product and/or a fragment or derivative of said transcription product is determined using a PCR analysis and/or Northern blot analysis.

10. The method according to any of claims 1 to 8 wherein said translation product and/or a fragment or derivative of said translation product is determined using an immunoassay, a Western blot analysis, an enzyme activity assay, and/or a binding assay.

11. The method according to any of claims 1 to 10, further comprising comparing a level and/or an activity of (i) a transcription product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (ii) a translation product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (iii) a fragment or derivative of said transcription or translation product in a series of samples taken from said subject over a period of time.

12. The method according to claim 11 wherein said subject receives a treatment prior to one or more of said sample gatherings.

13. The method according to claim 12 wherein said level and/or activity is determined before and after said treatment of said subject.

14. A method of treating or preventing a neurodegenerative disease, in particular Alzheimer's disease, in a subject comprising administering to said subject in a therapeutically or prophylactically effective amount an agent or agents which directly or indirectly affect an activity and/or a level of (i) a gene coding for a phosphoprotein enriched in astrocytes, and/or (ii) a transcription product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (iii) a translation product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (iv) a fragment or derivative of (i) to (iii).

15. A modulator of an activity and/or of a level of at least one substance which is selected from the group consisting of (i) a gene coding for a phosphoprotein enriched in astrocytes, and/or (ii) a transcription product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (iii) a translation product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (iv) a fragment or derivative of (i) to (iii).

16. A pharmaceutical composition comprising a modulator according to claim 15.

17. A modulator of an activity and/or of a level of at least one substance which is selected from the group consisting of (i) a gene coding for a phosphoprotein enriched in astrocytes, and/or (ii) a transcription product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (iii) a translation product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (iv) a fragment or derivative of (i) to (iii) for use in a pharmaceutical composition.

18. Use of a modulator of an activity and/or of a level of at least one substance which is selected from the group consisting of (i) a gene coding for a phosphoprotein enriched in astrocytes, and/or (ii) a transcription product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (iii) a translation product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (iv) a fragment or derivative of (i) to (iii) for a preparation of a medicament for treating or preventing a neurodegenerative disease, in particular Alzheimer's disease.

19. A kit, comprising in one or more containers, a therapeutically or prophylactically effective amount of the pharmaceutical composition of claim 16.

20. A recombinant, non-human animal comprising a non-native gene sequence coding for a phosphoprotein enriched in astrocytes, or a fragment thereof, or a derivative thereof, said animal being obtainable by: (i) providing a gene targeting construct comprising said gene sequence and a selectable marker sequence, and (ii) introducing said targeting construct into a stem cell of a non-human animal, and

(iii) introducing said non-human animal stem cell into a non- human embryo, and (iv) transplanting said embryo into a pseudopregnant non- human animal, and (v) allowing said embryo to develop to term, and (vi) identifying a genetically altered non-human animal whose genome comprises a modification of said gene sequence in both alleles, and

(vii) breeding the genetically altered non-human animal of step

(vi) to obtain a genetically altered non-human animal whose genome comprises a modification of said endogenous gene, wherein said disruption results in said non-human animal exhibiting a predisposition to developing a neurodegenerative disease or related disease or disorders.

21. The animal according to claim 20 wherein said phosphoprotein enriched in astrocytes is PEA-15.

22. Use of the recombinant, non-human animal according to claims 20 or 21 as an animal model for investigating neurodegenerative diseases, in particular Alzheimer's disease.

23. An assay for screening for a modulator of neurodegenerative diseases, in particular Alzheimer's disease, or related diseases or disorders of one or more substances selected from the group consisting of (i) a gene coding for a phosphoprotein enriched in astrocytes, and/or (ii) a transcription product of a gene coding for a phosphoprotein enriched in astrocytes, and/or

(iii) a translation product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (iv) a fragment or derivative of (i) to (iii), said method comprising : (a) contacting a cell with a test compound;

(b) measuring the activity and/or level of one or more substances recited in (i) to (iv); (c) measuring the activity and/or level of one or more substances recited in (i) to (iv) in a control cell not contacted with said test compound; and

(d) comparing the levels and/or activities of the substance in the cells of step (b) and (c), wherein an alteration in the activity and/or level of substances in the contacted cells indicates that the test compound is a modulator of said diseases or disorders.

24. A method of screening for a modulator of neurodegenerative diseases, in particular Alzheimer's disease, or related diseases or disorders of one or more substances selected from the group consisting of

(i) a gene coding for a phosphoprotein enriched in astrocytes, and/or

(ii) a transcription product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (iii) a translation product of a gene coding for a phosphoprotein enriched in astrocytes, and/or (iv) a fragment or derivative of (i) to (iii), said method comprising :

(a) administering a test compound to a test animal which is predisposed to developing or has already developed a neurodegenerative disease or related diseases or disorders in respect of the substances recited in (i) to (iv);

(b) measuring the activity and/or level of one or more substances recited in (i) to (iv);

(c) measuring the activity and/or level of one or more substances recited in (i) or (iv) in a matched control animal which is predisposed to developing or has already developed a neurodegenerative disease or related diseases or disorders in respect to the substances recited in (i) to (iv) and to which animal no such test compound has been administered;

(d) comparing the activity and/or level of the substance in the animals of step (b) and (c), wherein an alteration in the activity and/or level of substances in the test animal indicates that the test compound is a modulator of said diseases or disorders.

25. The method according to claim 24 wherein said test animal and/or said control animal is a recombinant animal which expresses a phosphoprotein enriched in astrocytes, or a fragment thereof, or a derivative thereof, under the control of a transcriptional control element which is not the native phosphoprotein enriched in astrocytes gene transcriptional control element.

26. A method of testing a compound, preferably of screening a plurality of compounds, for inhibition of binding between a ligand and a phosphoprotein enriched in astrocytes, or a fragment or derivative thereof, said method comprising the steps of:

(i) adding a liquid suspension of said phosphoprotein enriched in astrocytes, or a fragment or derivative thereof, to a plurality of containers;

(ii) adding a compound, preferably a plurality of compounds, to be screened for said inhibition of binding to said plurality of containers;

(iii) adding a detectable ligand, in particular a fluorescently detectable ligand, to said containers; (iv) incubating the liquid supension of said phosphoprotein enriched in astrocytes, or said fragment or derivative thereof, and said compound, preferably said plurality of compounds, and said ligand; (v) measuring amounts of detectable ligand or fluorescence associated with said phosphoprotein enriched in astrocytes, or with said fragment or derivative thereof; and

(vi) determining the degree of inhibition by one or more of said compounds of binding of said ligand to said phosphoprotein enriched in astrocytes, or said fragment or derivative thereof.

27. A method of testing a compound, preferably of screening a plurality of compounds, to determine the degree of binding of said compound or compounds to a phosphoprotein enriched in astrocytes, or to a fragment or derivative thereof, said method comprising the steps of: (i) adding a liquid suspension of said phosphoprotein enriched in astrocytes, or a fragment or derivative thereof, to a plurality of containers; (ii) adding a detectable compound, preferably a plurality of detectable compounds, in particular fluorescently detectable compounds, to be screened for said binding to said plurality of containers;

(iii) incubating the liquid suspension of said phosphoprotein enriched in astrocytes, or said fragment or derivative thereof, and said compound, preferably said plurality of compounds; (iv) measuring amounts of detectable compound or fluorescence associated with said phosphoprotein enriched in astrocytes, or with said fragment or derivative thereof; and (v) determining the degree of binding by one or more of said compounds to said phosphoprotein enriched in astrocytes, or said fragment or derivative thereof.

28. A method for producing a medicament comprising the steps of (i) identifying a modulator of neurodegenerative diseases, in particular Alzheimer's disease, by a method according to any of claims 23 to 25 and (ii) admixing the modulator with a pharmaceutical carrier.

29. A method for producing a medicament comprising the steps of (i) identifying a compound as an inhibitor of binding between a ligand and a phosphoprotein enriched in astrocytes by a method according to claim 26 and (ii) admixing the compound with a pharmaceutical carrier.

30. A method for producing a medicament comprising the steps of (i) identifying a compound as a binder to a phosphoprotein enriched in astrocytes by a method according to claim 27 and (ii) admixing the compound with a pharmaceutical carrier.

31. A medicament obtainable by any of the methods according to claim 28 to 30.

32. A medicament obtained by any of the methods according to claim 28 to 30.