WO2020034127A1

WO2020034127A1 - Compositions and methods for assessing or improving brain function, learning ability or memory

Info

Publication number: WO2020034127A1
Application number: PCT/CN2018/100721
Authority: WO
Inventors: Xiujie Wang; Zeyu ZHANG; Meng Wang; Dongfang Xie; Zenghui HUANG
Original assignee: Institute Of Genetics And Developmental Biology, Chinese Academy Of Sciences
Priority date: 2018-08-15
Filing date: 2018-08-15
Publication date: 2020-02-20
Also published as: CN112585270A; CN112585270B

Abstract

Compositions and methods for improving brain function or enhancing learning ability or memory are provided. The compositions may include one or more agents that increase METTL3 (N⁶-adenosine-methyltransferase 70 kDa subunit) potency in at least one body part of the subject. The methods may include administering, to a subject, a composition including one or more agents that increase METTL3 potency in at least one body part of the subject. Methods for assessing learning ability or memory ability of a subject are also provided. The methods may include assessing the level of an N⁶-methyladenosine (m⁶A) -related protein in at least one body part of the subject and comparing the level of m⁶A or the m⁶A-related protein to a standard level. The methods may further include determining the learning ability or memory ability of the subject based on the comparison of the level of m6A or the m6A-related protein to the standard level.

Description

COMPOSITIONS AND METHODS FOR ASSESSING OR IMPROVING BRAIN FUNCTION, LEARNING ABILITY OR MEMORY

TECHNICAL FIELD

The present disclosure generally relates to an assessment or improvement of physiological and/or psychological functions, and in particular, to compositions and methods for improving brain function, learning ability or memory, and methods for assessing brain function, learning ability or memory.

BACKGROUND

Memory ability and learning ability play important roles in people’s daily lives. Many people suffer from memory and learning disorders or deficits, such as agnosia, Alzheimer’s disease, amnesia, and dementia. These people generally have difficulties in remembering information and learning new skills, and thus, suffering from pain and worsening qualities of life. Moreover, people having normal memory and learning abilities generally desire to enhance such abilities, or to prevent the gradual memory and learning ability decline along aging. The memory and learning abilities depend greatly on the function of the brain to receive, store, consolidate and retrieve information. The brain function may relate to neuronal plasticity and the expression of certain genes (e.g., early response genes) . Therefore, it is desirable to develop compositions and methods for assessing and/or improving brain function, learning ability or memory in healthy subjects as well as subjects suffering from disorders or deficits.

SUMMARY

According to an aspect of the present disclosure, a method is provided. The method may include administering, to a subject to improve brain function or enhance learning ability or memory of the subject, a composition including one or more agents that increase METTL3 (N ⁶-adenosine-methyltransferase 70 kDa subunit) potency in at least one body part of the subject.

In some embodiments, the subject may be a human or animal.

In some embodiments, the subject may be suffering from a learning or memory disorder.

In some embodiments, the subject may have a learning or memory deficit.

In some embodiments, the subject may be suffering from agnosia, Alzheimer's disease, amnesia, traumatic brain injury, or dementia.

In some embodiments, the subject may be mentally healthy.

In some embodiments, the at least one body part of the subject may include the brain of the subject.

In some embodiments, the at least one body part of the subject may include the hippocampus of the subject.

In some embodiments, the one or more agents may be configured to increase METTL3 amount in the at least one body part.

In some embodiments, the one or more agents may include a METTL3 peptide.

In some embodiments, the one or more agents may include a Mettl3 cDNA sequence or a fragment of the Mettl3 cDNA sequence.

In some embodiments, the one or more agents may include an engineered carrier vector comprising a Mettl3 cDNA sequence or a fragment of the Mettl3 cDNA sequence.

In some embodiments, the one or more agents may include an engineered virus comprising Mettl3 cDNA sequence or a fragment of the Mettl3 cDNA sequence.

In some embodiments, the virus may include adenosine associated virus, adenosine virus, lentivirus, or sendai virus.

In some embodiments, the one or more agents may be configured to increase METTL3 expression by stimulating a positive factor that enhances METTL3 expression.

In some embodiments, the one or more agents may be configured to increase METTL3 expression by inhibiting a negative factor that reduces METTL3 expression.

In some embodiments, the one or more agents may include an antibody.

In some embodiments, the one or more agents may be configured to stimulate METTL3 activity in the at least one body part.

In some embodiments, the one or more agents may include a METTL3 agonist.

In some embodiments, the one or more agents may be configured to increase METTL3 activity by stimulating a positive factor that enhances METTL3 activity.

In some embodiments, the one or more agents may be configured to increase METTL3 activity by inhibiting a negative factor that reduces METTL3 activity.

In some embodiments, administering to a subject a composition may include administering the composition to the skin of the subject.

In some embodiments, administering to a subject a composition may include injecting the composition to the subject.

In some embodiments, administering to a subject a composition may include administering orally the composition to the subject.

In some embodiments, the composition may be configured as a suppository.

According to another aspect of the present disclosure, a method is provided. The method may include administering, to a subject to enhance learning ability of the subject, a composition including one or more agents that increase METTL3 (N ⁶-adenosine-methyltransferase 70 kDa subunit) potency in at least one body part of the subject.

According to another aspect of the present disclosure, a method is provided. The method may include administering, to a subject to enhance memory of the subject, a composition including one or more agents that increase METTL3 (N ⁶-adenosine-methyltransferase 70 kDa subunit) potency in at least one body part of the subject.

According to another aspect of the present disclosure, a method is provided. The method may include administering, to a subject to enhance long term memory consolidation of the subject, a composition including one or more agents that increase METTL3 (N ⁶-adenosine-methyltransferase 70 kDa subunit) potency in at least one body part of the subject.

According to another aspect of the present disclosure, a method is provided. The method may include administering, to a subject to enhance long term memory consolidation of the subject, a composition including one or more agents that increase METTL3 (N ⁶-adenosine-methyltransferase 70 kDa subunit) potency in the hippocampus of the subject.

According to another aspect of the present disclosure, a method is provided. The method may include administering, to a subject to improve brain function of the subject suffering from a mental disorder, a composition including one or more agents that increase METTL3 (N ⁶-adenosine-methyltransferase 70 kDa subunit) potency in the hippocampus of the subject.

According to another aspect of the present disclosure, a method is provided. The method may include administering, to a subject to enhance long term memory consolidation of the subject suffering from a memory deficit, a composition including one or more agents that increase METTL3 (N ⁶-adenosine-methyltransferase 70 kDa subunit) potency in the hippocampus of the subject.

According to another aspect of the present disclosure, a method is provided. The method may include administering, to a subject to enhance long term memory consolidation of the subject that may be not suffering from memory deficit, a composition including one or more agents that increase METTL3 (N ⁶-adenosine-methyltransferase 70 kDa subunit) potency in the hippocampus of the subject.

According to another aspect of the present disclosure, a method is provided. The method may include administering, to a subject to improve brain function or enhance learning ability or memory of the subject, a composition including one or more agents that increase N ⁶-methyladenosine (m ⁶A) abundance in at least one body part of the subject.

According to another aspect of the present disclosure, a method for assessing learning ability or memory ability of a subject is provided. The method may include assessing the level of an N ⁶-methyladenosine (m ⁶A) -related protein in at least one body part of the subject and comparing the level of m ⁶A or the m ⁶A-related protein to a standard level. The method may further include determining the learning ability or memory ability of the subject based on the comparison of the level of m ⁶A or the m ⁶A-related protein to the standard level.

In some embodiments, the m ⁶A-related protein may be the METTL3 protein.

In some embodiments, the standard level may be obtained by assessing the level of the m ⁶A-related protein in the at least one body part of subjects in a control group.

According to yet another aspect of the present disclosure, a composition is provided. The composition may be configured to improve brain function or enhance learning ability or memory of a subject. The composition may include one or more agents that increase METTL3 (N ⁶-adenosine-methyltransferase 70 kDa subunit) potency in at least one body part of the subject.

In some embodiments, the subject may be a human or animal.

In some embodiments, the subject may have a learning or memory deficit.

In some embodiments, the subject may be mentally healthy.

In some embodiments, the one or more agents may include a METTL3 peptide.

In some embodiments, the one or more agents may include an engineered carrier vector including Mettl3 cDNA sequence or a fragment of the Mettl3 cDNA sequence.

In some embodiments, the one or more agents may include an engineered virus including Mettl3 cDNA sequence or a fragment of the Mettl3 cDNA sequence.

In some embodiments, the one or more agents may include an antibody.

In some embodiments, the one or more agents may include a METTL3 agonist.

Additional features will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following and the accompanying drawings or may be learned by production or operation of the examples. The features of the present disclosure may be realized and attained by practice or use of various aspects of the methodologies, instrumentalities, and combinations set forth in the detailed examples discussed below.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure is further described in terms of exemplary embodiments. These exemplary embodiments are described in detail with reference to the drawings. It should be noted that the drawings are not to scale. These embodiments are non-limiting exemplary embodiments, in which like reference numerals represent similar structures throughout the several views of the drawings, and wherein:

FIGs. 1A-1F illustrate exemplary results indicating postnatal deletion of Mettl3 in hippocampus may prolong the process of long-term memory (LTM) consolidation according to some embodiments of the present disclosure;

FIGs. 2A-2D illustrate exemplary results indicating electrophysiological tests of Mettl3-depleted hippocampus according to some embodiments of the present disclosure;

FIGs. 3A-3D illustrate exemplary results indicating METTL3 regulates long-term memory formation via its m ⁶A methyltransferase function according to some embodiments of the present disclosure;

FIGs. 4A-4D illustrate exemplary results indicating m ⁶A methylome is dynamically regulated during memory consolidation;

FIGs. 5A-5F illustrate exemplary results indicating m ⁶A promotes the translation of immediate-early genes upon activity induction according to some embodiments of the present disclosure;

FIGs. 6A-6E illustrate exemplary results indicating overexpression of METTL3 enhances long-term memory formation according to some embodiments of the present disclosure;

FIG. 7 illustrates an exemplary proposed model according to some embodiments of the present disclosure;

FIGs. 8A-8H illustrate exemplary results indicating characterization of brain gross morphology of Mettl3 cKO mice according to some embodiments of the present disclosure;

FIGs. 9A-9F illustrate exemplary results indicating Mettl3 cKO mice show no difference in locomotion, exploration and anxiety as compared to CTRL according to some embodiments of the present disclosure;

FIGs. 10A-10C illustrate exemplary results indicating characterization of electrophysiological properties of cKO mice according to some embodiments of the present disclosure;

FIGs. 11A-11B illustrate exemplary results indicating analysis of transcriptomic change during early timepoints after training according to some embodiments of the present disclosure;

FIG. 12 illustrates exemplary results indicating validation of MeRIP-qPCR according to some embodiments of the present disclosure; and

FIGs. 13A-13B illustrate exemplary results indicating overexpression of Mettl3 in hippocampus or primary neurons according to some embodiments of the present disclosure.

DETAILED DESCRIPTION

The following description is presented to enable any person skilled in the art to make and use the present disclosure and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present disclosure. Thus, the present disclosure is not limited to the embodiments shown, but is to be accorded the widest scope consistent with the claims.

The terminology used herein is to describe particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a, ” “an, ” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises, ” “comprising, ” “includes, ” and/or “including” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof.

These and other features, and characteristics of the present disclosure, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, may become more apparent upon consideration of the following description with reference to the accompanying drawing (s) , all of which form a part of this specification. It is to be expressly understood, however, that the drawing (s) are for the purpose of illustration and description only and are not intended to limit the scope of the present disclosure. It is understood that the drawings are not to scale.

The present disclosure provides compositions and methods for improving brain function or enhancing learning ability or memory, and methods for assessing brain function, learning ability or memory ability. In some embodiments, the composition may include one or more agents that increase METTL3 (N ⁶-adenosine-methyltransferase 70 kDa subunit) potency in the at least one body part of the subject (e.g., the brain of the subject) . In some embodiments, the agent (s) may be configured to increase METTL3 amount or METTL3 activity in the at least one body part of the subject. In some embodiments, the subject may be mentally healthy or suffering from a learning disorder, a memory disorder, a learning deficit, a memory deficit, or the like, or any combination thereof. In some embodiments, the methods for improving brain function or enhancing learning ability or memory may include administering the above-mentioned composition to the subject. In some embodiments, the present disclosure also includes uses of the compositions herein disclosed in the manufacture of a medicament or food supplement for the treatment of a disorder or deficit in brain function, learning ability, or memory of a subject. In some embodiments, the present disclosure also includes uses of the compositions herein disclosed in the manufacture of a medicament or food supplement for the improvement of a disorder or deficit in brain function, learning ability, or memory of a subject. In some embodiments, the composition may be administered to the subject via an oral administration, an injection administration, a topical administration, etc. In some embodiments, the composition may be configured as a suppository. In some embodiments, the methods for assessing brain function, learning ability or memory ability of a subject may include assessing a level of N ⁶-methyladenosine (m ⁶A) or a level of m ⁶A-related protein (e.g., METTL3, METTL14) in at least one body part of the subject. In some embodiments, the assessed level of m ⁶A or m ⁶A-related protein may be compared to a standard level. In some embodiments, the brain function, learning ability or memory ability of the subject may be determined based on the comparison between the assessed level of m ⁶A (or m ⁶A-related protein) and the standard level. In response to a determination that the assessed level of m ⁶A (or m ⁶A related protein) is lower than the corresponding standard level, it may be determined that the subject has a relatively low level of brain function, learning ability or memory ability.

As used herein, the term “potency” refers to a total catalyzing ability of an enzyme (e.g., an RNA, a protein, a peptide or a fragment thereof) in a subject or a certain region (e.g., body part, tissue, or organ) of the subject. The region may include but is not limited to a whole body or a part of the body of the subject. In some embodiments, the subject may be a human or a non-human animal. In some embodiments, the part of the body may include an organ, a tissue, a vessel, or a part or combination thereof. Merely by way of example, the region may include a head, a brain, a hippocampus, a cortex, a prefrontal cortex, a neocortex, an amygdala, a striatum, a cerebellum, or the like, or any combination thereof. In certain embodiments, the region includes the hippocampus of a person. In some embodiments, the potency of an enzyme may be dependent on the total amount (or concentration) of the enzyme in the region and/or the activity of the enzyme in the region. The term “activity” of an enzyme refers to the catalyzing ability of a quantity unit of the enzymes in the region.

As used herein, the term “brain function” refers to the ability of the brain to receive, process and/or store various information, and/or control and/or modulate various biological activities. In some embodiments, the brain function may be affected or damaged by one or more factors such as aging, a traumatic brain injury, a tumor, a physiological disorder, or the like, or any combination thereof. If the brain function is abnormal, one or more abilities (e.g., comprehension, memory, reading, speaking, listening, vision, learning, etc. ) associated with the brain function of a subject may be affected. In some embodiments, the brain function may be improved by the composition and methods described in the present disclosure.

As used herein, the term “memory” refers to acquired information stored in the brain that can be retrieved, or the ability to encode, store, register, access, and/or retrieve the acquired information. In some embodiments, the terms “memory” and “memory ability” are used interchangeably in the present disclosure to refer to the ability to encode, store, register, access, and/or retrieve information. In some embodiments, the memory may include a short-term memory and/or a long-term memory. In some embodiments, the short-term memory may refer to a capability for holding a small amount of information in the brain for a short period of time (e.g., 1s, 2s, 3s, 4s, 5s, 10s, 15s, 20s, 25s, 30s, or the like) . In some embodiments, the short-term memory may be formed rapidly and may last for a relatively short period of time (e.g., one or more seconds, one or more minutes, one or more hours, or one or more days, or the like) . In some embodiments, the long-term memory may be a stage of the Atkinson–Shiffrin memory model in which informative knowledge may be held indefinitely. In some embodiments, the long-term memory may be formed less rapidly and may last for a relatively long period of time (e.g., one or more days, one or more weeks, one or more months, or one or more years, or the like) in comparison with the short-term memory. In some embodiments, newly acquired information may be initially stored in the brain in a fragile state and may tend to be gradually forgotten by the subject. In a memory consolidation process, the fragile state of the acquired information may be transformed into a relatively stable state in the brain, and accordingly, the acquired information is less likely to be forgotten by the subject. In some embodiments, the memory consolidation process may occur naturally over time or with the re-acquisition of the same acquired information (or related information) .

As used herein, the term “learning ability” refers to the ability to gain new information, knowledge, and/or skills by a process including experiencing, studying or receiving training, etc. In some embodiments, the learning ability may depend at least partly on the formation of memory. For instance, in a learning process, known information in an existing memory may be retrieved and used to generate new information, such as new understandings, knowledge, skills, or the like, or any combination thereof. In some embodiments, the new information may be stored in the brain for a further learning process. Thus, in some embodiments, if a subject suffers from a memory disorder, it may be indicated that the subject also suffers from a learning disorder. In some embodiments, if the brain function for receiving, processing and/or storing information is abnormal, a memory disorder and/or a learning disorder may be induced or indicated.

According to an aspect of the present disclosure, a composition configured to improve brain function or enhance learning ability or memory of a subject is provided. In some embodiments, the composition may include one or more agents that are configured to increase an m ⁶A level in at least one body part of the subject. In some embodiments, the composition may include one or more agents that are configured to increases METTL3 (N ⁶-adenosine-methyltransferase 70 kDa subunit) potency in at least one body part of the subject.

In some embodiments, the subject may be a human or an animal. For example, the subject may be an infant, a child, a teenager, a young adult, a middle-aged adult, or a senior adult. In some embodiments, the subject may be a vertebrate or an invertebrate. An exemplary animal may be a monkey, an orangutan, a tiger, a cat, a dog, a rabbit, a ferret, a pig, a gerbil, a hamster, a chinchilla, a rat, a mouse, a guinea pig, a hedgehog, a sugar glider, a chinchilla, a chipmunk, a squirrel, a fish, a tortoise, or the like, or any combination thereof. In some embodiments, the subject may be a mammal. In some embodiments, the subject may include a companion animal (also referred to as a “pet” ) , an animal of a protected species, an animal for scientific research, an animal assisting police services (e.g., a police dog) , or the like, or any combination thereof. In some embodiments, the animal for scientific research may include a normal animal model (e.g., an animal that has not received any experimental treatment) and/or a test animal model (e.g., an animal that has received one or more experimental treatments) . In some embodiments, the test animal model may have received one or more experimental treatments related to a toxicology test, a disease treatment test, a xenotransplation test, a drug test, a defense test, a behavior test (e.g., a long-term memory test, a short-term memory test, a learning test) . In some embodiments, the experimental treatment (s) may include but not be limited to administering a test composition (e.g., a drug, a supplementary supplement, or active ingredients thereof, or food, drink, or the like) to the test animal model, changing conditions for the growth and development of the test animal model, modifying one or more genes of the test animal model, or the like, or any combination thereof.

In some embodiments, the subject may be suffering from a learning deficit and/or a memory deficit. As used herein, the term “learning deficit” (also referred to as learning disability) may refer to a symptom that the subject abnormally has difficulty in learning information, knowledge and/or skills, or has a disease related to learning disability or reduced learning ability. As used herein, the term “memory deficit” may refer to a symptom that the subject abnormally has difficulty in encoding, storing, registering, accessing, and/or retrieving acquired information, or has a disease related to memory disability or reduced memory ability. In some embodiments, the subject may be suffering from a learning disorder and/or a memory disorder. As used herein, the term “learning disorder” may refer to a neurodevelopmental, neurostructural, or neurochemical problem in which a human of normal intellectual potential is encountering unusual difficulty with his/her academic functioning that cannot be explained by inadequate educational opportunity or emotional or sensory disabilities. As used herein, the term “memory disorder” may refer to a result of damage to one or more neuroanatomical structures or having neurochemical problems that hinder the storage, retention and/or recollection of memories. In some embodiments, the subject may be suffering from a disorder in the brain function for receiving, processing and/or storing information (i.e., a brain function disorder) , and this may lead to a memory disorder and/or a learning disorder. In some embodiments, the learning disorder, the learning deficit, the memory disorder, the memory deficit and/or the brain function disorder may be caused by one or more factors such as developmental problem, aging, a traumatic brain injury, a tumor, a physiological disorder, or the like, or any combination thereof. For example, the subject may be suffering from a traumatic brain injury, agnosia, Alzheimer’s disease, amnesia, dementia, Huntington’s disease, Parkinson’s disease, Wernicke-Korsakoff’s Syndrome, or the like, or any combination thereof. As another example, the subject may have a tumor located in or near the central nervous system (e.g., brain) , which may affect normal biological functions of the brain.

In some embodiments, the composition may be administered to the subject to treat or relieve the learning disorder, the learning deficit, the memory disorder, the memory deficit, and/or the brain function disorder. For instance, the composition may be configured to reduce, relieve or eliminate one or more symptoms of the learning disorder, learning deficit, the memory disorder, the memory deficit and/or the brain function disorder, and/or to reduce or slow further progression. In some embodiments, the composition may be administered to the subject to improve the ability of the brain to receive, process and store various information, and/or control and/or modulate various biological activities; enhance the ability of the subject to encode, store, register, access, and/or retrieve the acquired information; and/or enhance the ability of the subject to gain new information, knowledge, and/or skills.

In some embodiments, the subject may be mentally healthy. As used herein, the term “mentally healthy” refers to not having the learning disorder, the learning deficit, the memory disorder, the memory deficit and/or the brain function disorder as described above. A mentally healthy subject may have a normal learning ability, memory ability and/or brain function. In some embodiments, the composition may be administered to the mentally healthy subject to improve the brain function, enhance learning ability and/or memory of the subject, or to prevent the decline of learning and/or memory ability (e.g., along aging) . In some embodiments, the composition may be administered to a subject at a risk of having the learning disorder, the learning deficit, the memory disorder, the memory deficit and/or the brain function disorder, so as to prevent these and other disorders. In some embodiments, the subject may be a senior adult. In some embodiments, the subject may be an infant, a child, a teenager or an adult from a family with history of hereditary diseases related to the learning disorder, the learning deficit, the memory disorder, the memory deficit and/or the brain function disorder.

In some embodiments, the composition may include one or more agents configured to increase the potency of an m ⁶A methyltransferase. The m ⁶A methyltransferase may include but is not limited to METTL3, METTL14, Wilms tumor 1 associated protein (WTAP) , KIAA1429, or the like, or a fragment thereof, or any combination thereof. In some embodiments, the composition may include one or more agents configured to increase an m ⁶A abundance by reducing the potency of an m ⁶A demethylase. The m ⁶A demethylase may include but not limited to fat mass and obesity-associated protein (FTO) , AlkB homolog 5 (ALKBH5) , or the like, or a fragment thereof, or any combination thereof. In the following description, compositions and methods for increasing METTL3 potency are provided for illustration purposes and are not intended to limit the scope of the present disclosure. It should be noted that similar strategies may also be applied to compositions and methods for increasing the potency of one or more other m ⁶A methyltransferases or decreasing the potency of one or more m ⁶A demethylases, or other m ⁶A-related enzymes, or any combination thereof.

In some embodiments, the composition may include one or more agents that increase METTL3 potency in at least one body part of the subject. METTL3 is an N ⁶-adenosine-methyltransferase 70 kDa subunit. As used herein, the term “METTL3 potency” may refer to a total ability of the METTL3 to catalyze methylation of an RNA (e.g., mRNA) in the at least one body part of the subject. In some embodiments, the METTL3 may catalyze the methylation of an mRNA to promote translation of the mRNA. In some embodiments, the METTL3 may recognize a methylated mRNA and/or promote translation of the methylated mRNA. In some embodiments, the METTL3 may bind to chromatin. For instance, the METTL3 may bind to a DNA at a transcription start region (e.g., a promoter) . In some embodiments, the METTL3 may regulate memory formation and/or memory consolidation through promoting the translation of genes (e.g., neuronal early response genes) via m ⁶A dependent or m ⁶A independent mechanisms. In some embodiments, the METTL3 (or other m ⁶A methyltransferases) may enhance long-term potentiation (LTP) . As used herein, the term “long-term potentiation” refers to persistent strengthening of synapses based on recent patterns of synaptic activity. In some embodiments, the recent patterns of synaptic activity may produce a long-lasting increase in signal transmission between two neurons. In some embodiments, the enhancement of LTP may lead to an improvement in brain function, learning ability and memory (e.g., long-term memory) . In some embodiments, the agent (s) that increases METTL3 potency may be configured to increase the amount of the METTL3 in the at least one body part of the subject and/or the activity of a unit quantity of METTL3 in the at least one body part of the subject. In some embodiments, the at least one body part may include an organ, a tissue, or a part thereof. Merely by way of example, the at least one body part may include but is not limited to a head, a brain, a hippocampus, a cortex, a prefrontal cortex, a neocortex, an amygdala, a striatum, a cerebellum, or the like, or any combination thereof.

In some embodiments, the METTL3 potency may be increased by increasing the amount of METTL3 peptide in the at least one body part, or increasing the activity of the METTL3 peptide. As used herein, the term “METTL3 peptide” refers to a full length of METTL3 protein, or a fragment of METTL3 protein that retains the METTL3 potency (i.e., the ability of the METTL3 peptide to catalyze the methylation of an RNA (e.g., mRNA)) .

In some embodiments, the agent (s) that increase the METTL3 potency in the at least one body part may include a METTL3 peptide. In some embodiments, the agent (s) that increase METTL3 potency in the at least one body part may include a mettl3 cDNA sequence and/or a fragment of the mettl3 cDNA sequence. As used herein, the mettl3 cDNA sequence and/or the fragment thereof may refer to a DNA sequence that encodes the METTL3 peptide. In some embodiments, the agent (s) that increase the METTL3 potency in the at least one body part may include a METTL3 mRNA sequence and/or a fragment of METTL3 mRNA sequence. As used herein, the METTL3 mRNA sequence and/or the fragment of METTL3 mRNA sequence may refer to an mRNA transcribed according to the mettl3 cDNA sequence and/or the fragment of the mettl3 cDNA sequence. In some embodiments, the mettl3 cDNA sequence, the fragment of mettl3 cDNA sequence, the METTL3 mRNA sequence and/or the fragment of METTL3 mRNA sequence may increase the expression of the METTL3 peptide in the at least one body part, thereby increasing the amount of the METTL3 peptide in the at least one body part.

In some embodiments, the agent (s) that increase the METTL3 potency in the at least one body part may include an engineered METTL3 peptide, which refers to mutant forms of full-length METTL3 or METTL3 fragments that retain the catalytic activity, as well as peptides that include wild-type or mutant METTL3 peptide conjugated or linked to carrier agent. For example, the carrier agent may be carrier nanoparticle or a carrier peptide that is configured to facilitate the passage of the METTL3 peptide through the blood-brain barrier (BBB) . In certain embodiments, the carrier nanoparticle may be loaded with liposomes, thus facilitating the transfer of the engineered METTL3 peptide through the BBB. In certain embodiments, the carrier peptide may be a peptide with a sequence acquired from the BRAINPEPS database and capable of pass through the BBB, e.g. through active transportation.

In some embodiments, the agent (s) that increase the METTL3 potency in the at least one body part may include an engineered carrier vector including a mettl3 cDNA sequence or a fragment of the mettl3 cDNA sequence. In some embodiments, the agent (s) that increase the METTL3 potency in the at least one body part may include an engineered carrier vector including a METTL3 mRNA sequence or a fragment of METTL3 mRNA sequence. The carrier vector may include but is not limited to a plasmid, a cosmid, a synthesized nucleic acid, an artificial chromosome, etc. Merely by way of example, a mettl3 cDNA sequence, a fragment of mettl3 cDNA sequence, a METTL3 mRNA sequence and/or a fragment of METTL3 mRNA sequence may be incorporated into a nucleic acid, respectively, to generate an engineered nucleic acid. In some embodiments, the engineered nucleic acid may be directly used to transfect cells in the at least one body part of the subject.

In some embodiments, the agent (s) that increase the METTL3 potency in the at least one body part may include an engineered virus. The engineered virus may include a mettl3 cDNA sequence, a fragment of mettl3 cDNA sequence, a METTL3 mRNA sequence and/or a fragment of METTL3 mRNA sequence. In some embodiments, the engineered nucleic acid may be introduced into a virus to obtain the engineered virus. For instance, the virus may include an adenosine virus, an adenosine associated virus, a sendai virus (SeV) , a retrovirus, a polyomavirus, an Epstein-Barr virus, or the like, or any combination thereof. In some embodiments, the retrovirus may include one or more viruses from an Alpharetrovirus genus (e.g., an Avian leucosis virus) , a Beltaretrovirus genus (e.g., a mouse mammary tumor virus) , a Gammaretrovirus genus (e.g., a Murine leukemia virus) , a Deltaretrovirus genus (e.g., a bovine leukemia virus) , an Epsilonretrovirus genus (e.g., a Walleye dermal sarcoma virus) , a Lentivirus genus (e.g., a human immunodeficiency virus) , a Spumavirus genus (e.g., a simian foamy virus) , or the like, or any combination thereof. In some embodiments, the engineered virus may infect one or more cells in the at least one body part and the expression of METTL3 peptide may be increased in the at least one body part.

In some embodiments, the agent (s) that increase the METTL3 potency in the at least one body part may include a positive factor that enhances METTL3 expression. In some embodiments, the agent (s) that increase the METTL3 potency in the at least one body part may be configured to increase METTL3 expression by stimulating a positive factor that enhances METTL3 expression. For instance, the agent (s) may include a peptide, a lipid, a polysaccharide, a nucleic acid, a steroid, or any combination thereof.

In some embodiments, the agent (s) that increase the METTL3 potency in the at least one body part may be configured to increase METTL3 expression by inhibiting a negative factor that reduces METTL3 expression. In some embodiments, the negative factor that reduces METTL3 expression may include a microRNA (miRNA) , an antisense DNA, a small interfering RNA (siRNA) , or the like, or any combination thereof. In some embodiments, the miRNA, the antisense DNA and/or a complementary strand of the siRNA may bind to a METTL3 mRNA sequence or a fragment of METTL3 mRNA sequence via a base-paring mechanism, so that the METTL3 mRNA sequence may be silenced, and accordingly, the expression of METTL3 peptide may be inhibited. In some embodiments, the agent (s) that inhibit the negative factor may include an inhibiting factor of the miRNA, the antisense DNA, and/or the siRNA; an enzyme that degrades the miRNA, the antisense DNA, and/or the siRNA; a nucleic acid encoding the enzyme that degrades the miRNA, the antisense DNA, and/or the siRNA; a carrier vector including the nucleic acid encoding the enzyme that degrades the miRNA, the antisense DNA, and/or the siRNA; an engineered virus including the nucleic acid encoding the enzyme that degrades the miRNA, the antisense DNA, and/or the siRNA, or the like, or any combination thereof. Merely by way of example, the miRNA that reduces METTL3 expression may include a let-7g miRNA that targets the 3’-UTR (three prime untranslated region) of the METTL3 mRNA. An exemplary agent that inhibits the let-7g miRNA and increases METTL3 expression may include but is not limited to a mammalian hepatitis B X-interacting protein (HBXIP) or a fragment thereof. In some embodiments, the agent (s) that increase the METTL3 potency in the at least one body part may include an antibody. In some embodiments, the antibody may specifically bind with the negative factor that reduces METTL3 expression. For instance, the antibody may include IgG, IgM, IgA, IgD or IgE molecules, or an antigen-specific fragment thereof (e.g., a Fab fragment, a Fv fragment, a scFv fragment, a single domain antibody, a disulphide-linked scfv fragment, or the like) .

In some embodiments, the composition may include one or more agents configured to stimulate METTL3 activity in the at least one body part. In some embodiments, the agent (s) may include a METTL3 agonist. As used herein, the term “METTL3 agonist” refers to a substance that can increase the activity of METTL3 peptide. The activity of METTL3 may refer to the ability of a quantity unit of the METTL3 peptides in the at least one body part to catalyze the methylation of an RNA. In some embodiments, the METTL3 agonist may include a peptide, a lipid, a polysaccharide, a nucleic acid, a steroid, or any combination thereof. For instance, the METTL3 agonist may include a miRNA that promote the METTL3 to bind to an mRNA for methylation. Such miRNAs may include but are not limited to miR-423-3p, miR-1226-3p, miR-330-5p, miR-668-3p, miR-1224-5p, miR-1981, or the like, or any combination thereof.

In some embodiments, the agent (s) may be configured to increase METTL3 activity by stimulating a positive factor that enhances METTL3 activity. In some embodiments, the agent (s) may be configured to increase the activity of one or more miRNAs that promote the METTL3 peptide to bind to an mRNA. In some embodiments, the agent (s) may be configured to increase the expression of the one or more miRNAs that promote the METTL3 peptide to bind to an mRNA. For instance, the agent (s) may include an enzyme that facilitates the production of the one or more miRNAs, such as a Dicer peptide and/or a fragment of the Dicer peptide. As another example, the agent (s) may include a nucleic acid that encodes the Dicer peptide or the fragment of the Dicer peptide, and/or a fragment of the nucleic acid. As yet another example, the agent (s) may include a carrier vector or an engineered virus that includes the nucleic acid that encodes the Dicer peptide and/or the fragment of the Dicer peptide, and/or the fragment of the nucleic acid.

In some embodiments, the agent (s) may be configured to increase METTL3 activity by inhibiting a negative factor that reduces METTL3 activity. Merely by way of example, the negative factor may include one or more small ubiquitin-like modifier (SUMO) proteins. The SUMO protein (s) may be covalently attached to the METTL3 peptide to inhibit the catalyzing ability of the METTL3 peptide. For instance, the SUMO protein (s) may include SUMO-1, SUMO-2, SUMO-3, SUMO-4, or the like, or any combination thereof. In some embodiments, the agent (s) may inhibit the activity of one or more SUMO proteins. For example, the agent (s) may be an antibody that binds to the one or more SUMO proteins. In some embodiments, the agent (s) may inhibit the expression of the SUMO proteins.

In some embodiments, the agent (s) may increase the amount of METTL3 peptide and/or the activity of METTL3 peptide by at least about 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 95%, 100%, 150%, 200%, or 300%, or more.

In some embodiments, the composition for improving brain function and/or enhancing learning ability and/or memory may be orally administered to the subject. In some embodiments, the composition for oral administration may be formulated as a drug, a dietary supplement, a food additive, a drink additive, or the like, or any combination thereof. In some embodiments, the composition may be formulated in the form of tablets, granules, powder, micellas, liquids, suspensions, emulsions, or the like, or any combination thereof. In some embodiments, the composition may include a pharmaceutically acceptable carrier. The pharmaceutically acceptable carrier may need to be nontoxic and may not have a negative impact on the activity of the agent (s) that increase METTL3 potency in the composition. For instance, the pharmaceutically acceptable carrier may include an excipient, a diluent, an auxiliary component, or the like, or any combination thereof. Exemplary excipients may include but are not limited to an emulsifier, a flow agent, a flavoring agent, a coloring agent, or the like, or any combination thereof. In some embodiments, the pharmaceutically acceptable carrier may protect the agent (s) against oxidation and/or degradation caused by enzymes and low/high pH values, so as to maintain the efficacy of the composition. For instance, the pharmaceutically acceptable carrier may include a coating layer, a capsule, a microcapsule, a nanocapsule, or the like, or any combination thereof. In some embodiments, the pharmaceutically acceptable carrier may have a capability of a controlled release of the agent (s) that increase METTL3 potency. The controlled release may include but is not limited to a slow release, a sustained release, a targeted release, or the like, or any combination thereof. Merely by way of example, the pharmaceutically acceptable carrier may include hydrogel capsules, microcapsules or nanocapsules made of collagen, gelatin, chitosan, alginate, polyvinyl alcohol, polylactic acid, or the like, or any combination thereof.

In some embodiments, the composition for improving brain function and/or enhancing learning ability and/or memory may be a parenteral formulation. For example, the composition may be an injection formulation as a solution, a suspension, an emulsion, powder, or the like. In some embodiments, the composition in the form of powder may be dissolved or dispersed in a solution, a suspension or an emulsion before injection. In some embodiments, the injection formulation may further include other pharmaceutically injectable ingredients, such as glucose, sodium chloride, potassium chloride, or the like, or any combination thereof. In some embodiments, the composition may be administered to the subject via intravenous injection or intraperitoneal injection. In some embodiments, the composition may be stereotactically injected into the at least one body part or a region near the at least one body part to increase the METTL3 potency in the at least one body part. For example, the composition may be administered to a head, a brain, a hippocampus, a cortex, a prefrontal cortex, a neocortex, an amygdala, a striatum, a cerebellum, or the like, or any combination thereof.

In some embodiments, the composition may be formulated as (or configured as) a suppository. As used herein, a “suppository” refers to a dosage form that is inserted into the rectum, vagina, urethra, or the like, or any combination thereof. In some embodiments, the suppository may include a pharmaceutically acceptable carrier that contains the active ingredients of the composition (e.g., the one or more agents that increase METTL3 potency) . In some embodiments, the pharmaceutically acceptable carrier may gradually dissolve, melt, or degrade (e.g., in the rectum, vagina, urethra) to release the active ingredients for local or systemic effects. In some embodiments, the composition may be administered to the subject via vaginal administration, rectal administration, nasal administration (e.g., in the form of a nose drop) , auricular administration (e.g., in the form of an ear drop) , intramedullary administration, intra-articular administration, intra-pleural administration, or the like, or any combination thereof. In some embodiments, the composition may be applied to the skin of the subject. For instance, the composition may be formulated as powder, granules, nanoparticles, cream, a lotion, an ointment, a suspension, a solution, or the like. Merely by way of example, the composition may be smeared or sprayed onto the skin of the subject (e.g., the skin of the at least one body part, the skin of the region near the at least one body part) .

According to another aspect of the present disclosure, a method for improving brain function and/or enhance learning ability and/or memory of a subject is provided. In some embodiments, the method may include administering an effective amount of a composition including one or more agents that increase METTL3 potency (e.g., as described earlier in the present disclosure) in at least one body part of the subject.

In some embodiments, the subject may be a human or an animal. In some embodiments, the subject may be suffering from a learning or memory disorder. In some embodiments, the subject may have a learning or memory deficit. In some embodiments, the subject may be suffering from agnosia, Alzheimer’s disease, amnesia, a traumatic brain injury, dementia, Huntington’s disease, Parkinson’s disease, Wernicke-Korsakoff’s Syndrome, or the like, or any combination thereof. In some embodiments, the subject may be mentally healthy. In some embodiments, the at least one body part of the subject may include a head, a brain, a hippocampus, a cortex, a prefrontal cortex, a neocortex, an amygdala, a striatum, a cerebellum, or the like, or any combination thereof.

In some embodiments, the composition may include one or more agents configured to increase METTL3 potency in the at least one body part. In some embodiments, the agent (s) may include a METTL3 peptide. In some embodiments, the agent (s) may include a Mettl3 cDNA sequence and/or a fragment of the Mettl3 cDNA sequence. In some embodiments, the agent (s) may include an engineered carrier vector including the Mettl3 cDNA sequence and/or the fragment of the Mettl3 cDNA sequence. In some embodiments, the agent (s) may include an engineered carrier vector including a METTL3 mRNA sequence and/or a fragment of the METTL3 mRNA sequence. In some embodiments, the agent (s) may include an engineered virus including the Mettl3 cDNA sequence and/or the fragment of the Mettl3 cDNA sequence. In some embodiments, the agent (s) may include an engineered virus including the METTL3 mRNA sequence and/or the fragment of the METTL3 mRNA sequence. More descriptions regarding the composition including the agent (s) that increases METTL3 potency may be found elsewhere in the present disclosure.

In some embodiments, the composition for improving brain function and/or enhancing learning ability and/or memory may be orally administered to the subject. In some embodiments, the composition for improving brain function and/or enhancing learning ability and/or memory may be administered to the subject via a parenteral administration, such as an intravenous injection, an intraperitoneal injection. In some embodiments, the composition may be stereotactically injected into the at least one body part or a region near the at least one body part to increase the METTL3 potency in the at least one body part. For example, the composition may be administered to a head, a brain, a hippocampus, a cortex, a prefrontal cortex, a neocortex, an amygdala, a striatum, a cerebellum, or the like, or any combination thereof. In some embodiments, the composition may be administered to the subject via vaginal administration, rectal administration, nasal administration, auricular administration, intramedullary administration, intra-articular administration, intra-pleural administration, or the like, or any combination thereof. In some embodiments, the composition may be applied to the skin of the subject. For instance, the composition may be formulated as powder, granules, nanoparticles, cream, a lotion, an ointment, a suspension, a solution, or the like. Merely by way of example, the composition may be smeared or sprayed onto the skin.

In some embodiments, the composition may be administered to the subject once a day, twice a day, three times a day, four time a day, etc. In some embodiments, the composition may be administered to the subject once every other day, once every three days, once a week, once every two weeks, once a month, etc.

In some embodiments, the composition may be used in combination with other drugs and/or dietary supplements for improving brain function and/or enhancing learning ability and/or memory. Exemplary drugs for improving brain function and/or enhancing learning ability and/or memory may include but are not limited to donepezil, rivastigmine, galantamine, metantine, or the like, or any combination thereof. Exemplary core ingredients of the dietary supplements may include acetyl-l-carnitine, bacopa monnieri, citicoline, curcumin, ginseng, huperzine A, or the like, or any combination thereof.

According to yet another aspect of the present disclosure, a method for assessing learning ability and/or memory ability of a test subject is provided. The method may include: (a) assessing a level of N ⁶-methyladenosine (m ⁶A) and/or a level of one or more m ⁶A-related proteins in at least one body part of the test subject; (b) comparing the level of m ⁶A and/or the level of the m ⁶A-related protein to a standard level; and (c) determining (or evaluating) the learning ability and/or memory ability of the test subject based on the comparison result of (b) .

In some embodiments, the at least one body part may include an organ, a tissue, a vessel, or the like, or a part thereof, or any combination thereof. In some embodiments, the at least one body part may include the entire body of the test subject. In some embodiments, the at least one body part may include one or more regions of the test subject. An exemplary region may include a head, a brain, a hippocampus, a cortex, a prefrontal cortex, a neocortex, an amygdala, a striatum, a cerebellum, or the like, or any combination thereof.

In some embodiments, to assess the level of m ⁶A and/or the level of m ⁶A-related protein (s) , one or more biological samples may be obtained from the test subject. In some embodiments, the biological sample (s) may include but is not limited to a tissue sample, a cell sample, a body fluid sample, or the like, or a combination thereof. An exemplary body fluid sample may include a blood sample, a mucous sample, a seminal fluid sample, a saliva sample, a urine sample, a breast milk sample, an interstitial fluid, a cerebrospinal fluid, a lymphatic fluid, or the like, or any combination thereof. In some embodiments, the biological sample (s) may be obtained from the at least one body part (e.g., the hippocampus) . In some embodiments, the biological sample (s) may be obtained from one or more other body parts of the test subject to assess the level of m ⁶A and/or the level of m ⁶A-related protein (s) in the at least one body part. For example, the biological sample (s) may include an intravenous blood sample obtained from a vein of the test subject. In some embodiments, the biological sample (s) may be obtained from the at least one body part at any timepoint. In some embodiments, the biological sample (s) may be obtained from the at least one body part after a learning test and/or a memory test. In some embodiments, the biological sample may be obtained from the at least one body part after the test subject receives a certain amount of training (i.e., there are learning and/or memory activities in the test subject) .

In some embodiments, the biological sample (s) may be subjected to a pretreatment to obtain a pretreated biological sample. In some embodiments, in the pretreatment, the biological sample (e.g., a tissue sample) may be smashed. In some embodiments, in the pretreatment, the biological sample may contain cells and may be subjected to a cell membrane disruption process to release intracellular RNA or proteins. Exemplary operations for disrupting cell membranes may include homogenization, ultrasonic wave treatment, organic solvent treatment, acid treatment, alkaline treatment, or the like, or any combination thereof. In some embodiments, total proteins may be extracted from the biological sample to obtain the pretreated biological sample. In some embodiments, total RNA may be extracted from the biological sample (s) . In some embodiments, a portion of the total RNA that satisfies a predetermined condition may be isolated to obtain the pretreated biological sample for measuring the level of m ⁶A. In some embodiments, the predetermined condition may relate to the integrity of the RNA. For instance, the integrity of RNA may be tested by agarose gel electrophoresis. In some embodiments, RNA samples with 28S and 18S ribosomal RNA gel bands at an approximate ratio of 2: 1 may be isolated to obtain the pretreated biological sample. In some embodiments, the pretreated biological sample may be used for quantitatively or qualitatively measuring the level of m ⁶A.

In some embodiments, the level of m ⁶A may refer to a degree of m ⁶A modifications on the RNA (e.g., mRNA) in the at least one body part. In some embodiments, the level of m ⁶A may be evaluated by the intensity of m ⁶A sites of methylation (i.e., m ⁶A peak intensity) of all the RNA in the pretreated biological sample. In some embodiments, the level of m ⁶A may be evaluated by the intensity of m ⁶A sites of methylation of the mRNAs transcribed according to a group of target genes. In some embodiments, the group of target genes may be selected from a set of genes associated with memory and/or learning ability. For instance, the group of target genes may include immediate early genes (IEGs) . In some embodiments, the IEGs may include but are not limited to Arc, Btg2, Egr1, c-Fos, Npas4, Nr4a1, or the like, or any combination thereof. In some embodiments, the IEGs may be rapidly activated after learning. In some embodiments, the IEGs may be indispensable for long-term memory formation.

Exemplary methods for assessing the level of m ⁶A may include liquid chromatography–mass spectrometry/mass spectrometry (LC-MS/MS) , a colorimetric method, a methylation individual-nucleotide-resolution crosslinking and immunoprecipitation-sequencing (miCLIP-seq) method, a methylated RNA immunoprecipitation-quantitative polymerase chain reaction (MeRIP-qPCR) method, or the like, or any combination thereof. In some embodiments, the method for assessing the level of m ⁶A may include contacting the pretreated biological sample with an agent that may specifically bind to the m ⁶A. In some embodiments, the agent may be marked with a detectable label. For instance, the agent may include an antibody or a fragment thereof that specifically binds to the m ⁶A. As another example, the label may include a fluorescent label, an isotope label, or the like, or any combination thereof. The level of m ⁶A may be assessed based on the detectable label.

In some embodiments, the m ⁶A-related protein (s) may include an m ⁶A methyltransferase, an m ⁶A demethylase, or the like, or any combination thereof. For example, the m ⁶A methyltransferase may include but is not limited to METTL3, METTL14, WTAP, KIAA1429, or the like, or a fragment thereof, or any combination thereof. As another example, the m ⁶A demethylase may include but is not limited to FTO, ALKBH5, or the like, or a fragment thereof, or any combination thereof. In certain embodiments, the m ⁶A-related protein is METTL3.

In some embodiments, methods for assessing the level of the m ⁶A-related protein (s) may include assessing the expression level of the m ⁶A-related protein (s) and/or assessing the activity level of the m ⁶A-related protein (s) . In some embodiments, the expression level of the m ⁶A-related protein (s) may be assessed by measuring the mRNA level of the m ⁶A-related protein (s) and/or the amount of the m ⁶A-related protein (s) in a unit volume or unit mass of the biological sample (s) (or pretreated biological sample) . Exemplary methods for assessing the mRNA level of the m ⁶A-related protein may include but are not limited to polymerase chain reaction (PCR) , reverse transcriptase PCR (RT-PCR) , in situ hybridization, Northern blot, sequence analysis, microarray analysis, detection of a reporter gene, or the like, or any combination thereof. Exemplary methods for assessing the amount of the m ⁶A-related protein (s) in a unit volume or unit mass of the biological sample (s) may include but are not limited to gel electrophoresis, MS, quantitative dot blot (QDB) analysis, spectrophotometry (e.g., the bicinchoninic acid assay (BCA assay) , or the like, or any combination thereof. Exemplary methods for assessing the activity level of the m ⁶A-related protein (s) may include but are not limited to an enzyme-linked immunosorbant assay (ELISA) , Western-blot, Dotting-blot, or the like, or any combination thereof.

In some embodiments, the standard level may be obtained by assessing the level of the m ⁶A and/or the m ⁶A-related protein (s) in the at least one body part of each reference subject in a control group, for example, by using the methods described above. In some embodiments, the reference subjects in the control group may be mentally healthy. In some embodiments, the reference subjects in the control group may have normal learning abilities and/or memory abilities. In some embodiments, the standard level may be a standard threshold or a standard level range determined based on statistical analysis of the levels of the m ⁶A and/or the m ⁶A-related protein (s) in the at least one body parts of the reference subjects in the control group.

In some embodiments, in order to assess the learning ability and/or the memory ability of a test subject, the same assessment methods as the control group may be used for assessing the level of the m ⁶A and/or the m ⁶A-related protein (s) in the at least one body part of the test subject. In some embodiments, the assessment result regarding the level of the m ⁶A and/or the m ⁶A-related protein (s) of the test subject may be compared with the standard level of the m ⁶A and/or the standard level of the m ⁶A-related protein (s) . For instance, if the assessment result is higher than or equal to the standard threshold, or falls within the standard level range, it may be determined that the learning ability and/or memory ability of the test subject is normal. If the assessment result is lower than the corresponding standard threshold, or does not fall within the standard level range, it may be determined that the test subject may have a disorder or deficit in the learning ability and/or memory ability. In some embodiments, the learning ability and/or memory ability of the test subject may be evaluated based on a comprehensive analysis. For instance, other factors to be considered in the comprehensive analysis may include whether there is a symptom of a disorder or deficit in the learning ability and/or memory ability, a neuropsychological test result, a magnetoencephalography (MEG) testing result, a brain imaging assessment (e.g., Computed Tomography (CT) , Magnetic Resonance Imaging (MRI) , or Positron Emission Tomography (PET)) result, or the like, or any combination thereof.

The present disclosure is further described according to the following examples, which should not be construed as limiting the scope of the present disclosure.

EXAMPLES

Materials and methods

Animals

All mice used in the Examples were born and raised in a temperature-controlled (22±1 ℃) room within ventilated cages inside a specific-pathogen-free barrier, with a 12-hour light/dark lighting cycle (7: 30 to 19: 30 light hours) and about 50%humidity. Pups were kept with their dams after born and weaned at postnatal day 21, then group housed by sex with 4 to 5 mice per cage and ad libitum access to food and water. All wildtype mice used in the process were in C56BL/6J genetic background and bought from Vital River Laboratory (Beijing) . To generate Mettl3 conditional knockout mice, Mettl3 ^flox/flox mice were first crossed with CaMKIIα-Cre mice (Jax #005359) to generate heterozygous mice (Mettl3 ^flox/+; CamKIIα-Cre) , the heterozygous mice were then crossed with either heterozygous or Mettl3 ^flox/flox mice to generate cKO mice (Mettl3 ^flox/flox; CamKIIα-Cre) and littermate CTRL mice (Mettl3 ^flox/flox) . The genotype of each mouse was determined by the genomic DNA extracted from tail tip tissue. All experiments followed the guidelines of the Animal Care and Use Committee of the Institute of Genetics and Developmental Biology, Chinese Academy of Sciences.

General conditions of behavioral tests

All behavioral tests were carried out on male mice at 8 to 12 weeks of age. Each test was conducted at fixed day time (between 8: 30 m to 18: 30 pm) on each training day. Animals were handled 2 min for 3 days and transferred to the testing room 24 hours prior to the behavioral tests, and those participated in multiple tests were allowed to rest for at least 3 days between two tests. Unless otherwise indicated, the apparatuses were cleaned with 75%ethanol after testing each mouse to prevent any bias caused by olfactory cues. All behavioral tests were carried out with the presence of two researchers blinded to the genotype.

Elevated-plus maze test

The elevated-plus maze apparatus consists of two opposite open arms (10×35 cm) and two opposite closed arms (10×35×15 cm) . The arms were connected to a central square (10×10 cm) and installed onto a high rack (60 cm above the ground) . The maze was made of opaque plastic in blue color. Each mouse was gently placed in the central zone of the maze facing one of the open arms, then recorded by an overhanging video camera for 10 min. The time spent by each mouse in different arms was analyzed by EthoVision XT 13 (Noduls) .

Open field test

Open-field box (40×40×35 cm) was made of opaque plastic in white color. Each mouse was gently placed in the central zone of the box and allowed to explore freely for 10 min, and recorded by an overhanging video camera. The total moving distance and time spent in the center zone of the box for each mouse were calculated by EthoVision XT 13 (Noduls) .

Rotarod test

Mice (4 per group) were gently placed on a rotating rod (UGO Basile) with an initial speed of 4 rpm for 30 s, then accelerated from 4 rpm to 50 rpm in 5 min. The latency of each mouse falling off the rod was recorded by an electrical relay below the rod. Each mouse was tested 3 times with 3 hours break between each trail.

Novel object recognition test

The novel object recognition test was carried out using the same apparatus as the open field test. Mice were placed into the open field box to habituate for 10 min on the first day. On the second day, each mouse was gently placed in the center of the box, with two objects (aT-25 flask filled with red ink and a 50 ml centrifuge tube filled with water) located in the center zone, and allowed to explore freely for 10 min, then sent back to their home cage. After 30 min, the mice were placed back to the box (with one object changed to a 10 cm tall vase) again for 5 min for retention test. The behavior of each mouse was recorded by EhtoVision XT 13. Frequencies (f) investigating each object were manually scored by two experienced researchers. Discrimination index was calculated as (f _novel-f _famliar) / (f _novel+f _familiar) ×100%.

Morris water maze test

Morris water maze test was carried out in a circular tank filled with water (120 cm in diameter and 30 cm in depth, made opaque by adding titanium dioxide, maintained at 21±1 ℃) in a room with fixed environment. A circular platform (9 cm in diameter) was submerged below the water surface at the center of the target quadrant. For each trial, mouse was gently placed into the water facing the tank wall within one of the four quadrants and allowed to swim for a maximum of 60 s to locate the hidden platform. The releasing quadrant was randomly changed every trial. Mice failed to find the platform were guided toward it with a long metal stick and allowed to stay on the platform for 5 s (testing association between METTL3 protein abundance with learning) or 30 s (all other experiments) . Mice were trained twice per day with an interval of 6 hours (starting at 8: 00 am and 14: 00 pm, respectively) . During the probe tests, the platform was removed, and mice were allowed to swim for 60 s. The first probe test was carried out on day 4 prior to day 4’s training (16 hours after day 3’s last training) , and the second probe test was carried out on day 6, 24 hours after day 5’s last training. The swimming path and time spent in each quadrant were recorded and analyzed by EthoVision XT 13 (Noduls) .

Contextual fear conditioning test

Mice were gently put into the conditioning box (Panlab, Harvard Apparatus) individually and allowed to explore for 2 min, followed by either one mild electric foot shock (0.8 mA for 2 s) or three mild foot electric shocks (0.8 mA for 2 s each with 60 s interval) . Mice were allowed to stay in the conditioning box for another 60 s, then returned to their home cage. Thirty minutes (short-term test) or 24 hours later (long-term test) , mice were put back to the conditioning box for 5 min. Freezing behavior was recorded and analyzed by PACKWIN 2.0.5 software (Panlab, Harvard Apparatus) .

Immunohistochemistry

Fresh or perfused brain samples were drop-fixed within 4%paraformaldehyde (PFA) in 1×PBS at 4 ℃ for 48 hours, then washed by 1×PBS twice, cryoprotected with 30%sucrose, frozen in Tissue Freezing Medium (TFM, General Data) , and sectioned (25-35 μm thick) with a cryostat (Leica) . Sections were permeabilized and blocked by blocking buffer containing 0.2%Triton X-100 and 2%bovine serum in 1×PBS for 30 min at room temperature. Sections were then incubated with primary antibodies diluted with blocking buffer at 4 ℃ overnight, and secondary antibodies diluted with blocking buffer for 2 hours at room temperature. Nuclei were stained by 4’, 6-diamidino-2-phenylindole (DAPI) with mounting medium (Vectorlabs, #H-1200) . Antibodies used for immunofluorescent labeling were as follows: anti-METTL3 (1: 200, Abcam, ab195352) , anti-CUX1 (10 μg/ml, Abcam, ab54583) , goat-anti-rabbit Alexa Fluor 594 (1: 500, Abcam, ab150080) , and goat-anti mouse Alexa Fluor 488 (1: 500, Abcam, ab150113) . Images were acquired using Leica SP8 confocal microscope.

Hematoxylin-eosin (HE) staining

Brain tissues (fixed in 4%PFA at 4 ℃ for at least 48 hours) were automatically dehydrated by Tissue-Tek VIP5Jr (Sakura) and embedded in paraffin (56-58 ℃) with Tissue-Tek TEC 5 Tissue Embedding Console System (Sakura) . Brain paraffin blocks were cut into 8-μm thick sections by a manual rotary microtome (Leica, RM2235) , and the sections were affixed onto poly-D-lysine coated microscope slides (CITOGLAS, 10127105P) . For hematoxylin-eosin staining, sections were first dewaxed in xylene (2 times, 10 min each) and rehydrated in alcohol (sequentially 100%alcohol 5 min, 95%alcohol 3 min, 70%alcohol 3 min, and rinsed in distilled water) , then automatically stained by Tissue-Tek Multiple Slide Stainer (Sukara, DRS 2000) . The stained sections were dehydrated in 100%alcohol (3 times, 5 min each) , cleared in xylene (3 times, 5 min each) and mounted in neutral balsam (Solarbio, G8590) . Whole-slide images were obtained by scanning the slides with NanoZoomer RS canner (Hamamatsu) .

Nissl staining

Nissl staining was performed using a staining kit (Coolabler, DZSL0135) following the manufacture’s instruction. Briefly, paraffin-embedded sections were dewaxed and hydrated following the same protocol as described in HE staining. Sections were then stained in cresyl violet staining solution at 56 ℃ (in a 56 ℃ incubator) for 1 h, washed by distilled water and then submerged into the differentiation solution provided by the kit until the background became clear. Stained sections were next dehydrated in 100%alcohol (3 times, 5 min each) , cleared in xylene (2 times, 5 min each) , and mounted in neutral balsam (Solarbio, G8590) . Whole-slide images were obtained by scanning the slides with NanoZoomer RS scanner (Hamamatsu) .

TUNEL staining

TUNEL staining was performed using in situ cell death detection kit (Roche, 11684809910) following the manufacture’s instruction. Briefly, cryopreserved tissue sections (prepared following procedures described in the immunohistochemistry experiment) were post-fixed with 4%PFA in 1×PBS for 20 min at room temperature, then washed with 1×PBS for 30 min, and permeabilized with 0.1%Triton X-100 in 0.1%sodium citrate for 2 min at 4 ℃. Each tissue section was stained with 50 μL label solution plus 50 μl enzyme solution in a humidified 37 ℃ incubator for 1 h, rinsed in 1×PBS for 3 times, then counter stained with DAPI following procedures described in the immunochemistry experiment. Slides were imaged using a Leica fluorescence microscope (DMI 3000B) . Positive and negative control staining samples were performed following the manufacture’s instruction to confirm the validity of the staining results (data not shown) .

Electrophysiological recordings

Mice (8 weeks) were deeply anesthetized by pentobarbital sodium (2%, 0.3 ml/100 g) and decapitated. The brains were rapidly removed and kept in ice-cold artificial cerebrospinal fluid (ACSF, in mM: 124 NaCl, 2.5 KCl, 1.2 NaH ₂PO ₄, 24 NaHCO ₃, 12.5 D-glucose, 2 CaCl ₂, and 1.5 MgSO ₄, saturated with 95 %O ₂ and 5 %CO ₂, pH adjusted to 7.3, and osmolarity adjusted to ～295 mOsm with sucrose) . Hippocampal acute brain slices (300 μm thick) were prepared with a vibratome (Leica) which was filled with ice-cold ACSF and incubated within oxygenated ACSF at room temperature for 1 hour. Then individual brain slices were transferred to a recording chamber bubbled with oxygenated ACSF at 31±1 ℃ (2 ml/min perfusion rate) . CA1 pyramidal neurons were visually targeted by using an Olympus microscope (Olympus BX50-WI) . Patch pipettes with 4-6 MΩ resistance were pulled from 110 mm borosilicate glass capillaries (Sutter Instrument) . The internal solution used was (in mM) : 140 K-gluconate, 2 MgCl ₂, 8 KCl, 10 HEPES, 0.2 Na-GTP, 2 Na2-ATP (pH=7.3) . Recordings and analysis were performed by Axopatch 700B amplifier (AXON) , Digidata 1440A (Molecular Devices) and pCLAMP 10.6 software (Molecular Devices) . The series and input resistances were monitored throughout each experiment, cells simultaneously satisfying the following requirements (high seal resistance>1 GΩ, series resistance below 25 MΩ, series resistance and input resistance changed less than 15%) were included for further analysis.

Miniature excitatory postsynaptic current (MEPSC) was recorded at -70 mV by holding the cells under whole-cell voltage-clamp mode. To isolate AMPA receptor-mediated mEPSCs, recordings were obtained in ACSF with 1 μM TTX and 100 μM PTX. Each cell was recorded for at least 5min. Action potential (AP) was recorded under whole-cell current-clamp mode and was evoked by a series of depolarizing current pulses (500 ms) from -60 to 500 pA with a 20 pA step increment. A single 500 pA current (500 ms) was injected to measure the inter-spike intervals, and 3 repeated -20 pA currents (800 ms) were injected to measure the fast/slow after-hyperpolarizing potentials (f/sAHPs) .

Short-term plasticity and long-term potentiation measurement

Acute brain slices (380 μm) were prepared as described above and incubated in oxygenated ACSF at room temperature for 1.5 h. Individual slices were transferred to recording chamber bubbled with oxygenated ACSF at 31±1 ℃ (6 ml/min perfusion rate) . Extracellular recording electrodes were filled with ACSF and positioned at the stratum radiatum of CA1 area of dorsal hippocampus. Concentric stimulation electrode was placed in sradiatum of CA3. Each recording started with measuring the input/output ratio by adjusting the stimulus intensity from 0 to 80 μA with an increment of 5 μA. Paired pulse ratio (PPR) was assessed by applying a succession of paired pulses separated by time intervals of 20 ms, 50 ms, 100 ms, and 200 ms. Waiting for 0.5-1 h, the same brain slice was further recorded for long-term potentiation (LTP) . Stimulation intensity was set by eliciting 40%of a maximal response as the baseline level. A stable baseline was achieved for at least 30 min prior to theta-burst stimulation (TBS) . Then the LTP was recorded for 1 h.

Virus preparation

The cDNA of Mettl3 gene was amplified from mouse, and cloned into the T-vector (TransGen, CB101) . The DPPW motif (residues 395–399) of Mettl3 (widetype Mettl3) , which is important for AdoMet binding, was mutated into APPA (mutated Mettl3) by PCR site-directed mutagenesis. The wildtype Mettl3 and mutated Mettl3 were subcloned into pAAV2/DJ-CMVMSC-RFP vector (HANBIO) . The pAAV-RC and pHelper were co-transfected with pAAV2/DJCMV-wildtype-Mettl3-RFP (AAV2/DJ-WT-Mettl3) , pAAV2/DJ-CMV-mutated-Mettl3-RFP (AAV2/DJ-Mut-Mettl3) or pAAV2/DJ-CMV-MSC-RFP (AAV2/DJ-RFP) into AAV-293 cells by using LipoFiter transfection reagent (HANBIO) to generate the adeno-associated virus (AAV) . Propagated AAV2/DJ in the AAV-293 cells were purified and the titer of virus was measured by plaque assays. The stock solutions of AAV2/DJ-WT-Mettl3, AAV2/DJ-Mut-Mettl3 and AAV2/DJ-RFP were 1.0-1.2×10 ¹² plaque formation unit (PFU) /ml, respectively. Primers used in the examples are listed in Table 1.

Table 1. Primers used for vector construction and qRT-PCR

Stereotaxic injection

Adult mice (8 weeks) were anesthetized with isoflurane and placed in a stereotaxic apparatus (RWD) . Viruses were delivered via a Hamilton syringe at a rate of 0.1 ul per minute, and needles were kept still for an additional 1 min before withdrawing. One microliter AAV2/DJ viruses carrying wildtype Mettl3, mutated Mettl3 or RFP (all 1.0-1.2×10 ¹² PFU/ml) , respectively, were bilaterally injected into the dorsal hippocampus (relative to bregma: AP=-1.9 mm, ML=±1.2 mm, DV=-1.3 mm) . After the surgery, mice were kept on a warm pad for a short period of recovery, then returned to their home cage and monitored for 24 hours. Mice were housed for 2 weeks after surgery before behavioral tests.

RNA isolation

TRNzol Universal (TIANGEN, DP424) was used to extract total RNA from cells or hippocampal tissue. RNA concentration was measured using NanoPhotometer P330 (Implen) , and only samples with OD 260/280 nm ratio of ～2.0 were used for subsequent experiments. The integrity of RNA was tested by agarose gel electrophoresis of total RNA, and only RNA samples with 28S and 18S ribosomal RNA gel bands at an approximate ratio of 2: 1 were used for further study.

Methylated RNA immunoprecipitation

Methylated RNA immunoprecipitation (MeRIP) was performed using Epimark N ⁶-Methyladenosine Enrichment Kit (NEB, E1610S) . Briefly, 2 μl m ⁶A antibody was attached to protein G magnetic beads (NEB, S1430) . Then, 100 μg total RNA with m ⁶A control RNA (Gaussia luciferase, GLuc) and unmodified control RNA (Cypridina luciferase, CLuc) was incubated with beads at 4 ℃ for 1 h. The beads were separately washed twice with reaction buffer (150 mM NaCl, 10 mM Tris-HCl, pH 7.5, 0.1%NP-40 in nuclease free H ₂O) , low salt reaction buffer (50 mM NaCl, 10 mM Tris-HCl, pH 7.5, 0.1%NP-40 in nuclease free H ₂O) , and high salt reaction buffer (500 mM NaCl, 10 mM Tris-HCl, pH 7.5, 0.1%NP-40 in nuclease free H ₂O) . The enriched m ⁶A-containing RNA was purified by phenol–chloroform extraction.

qRT-PCR

The extracted RNA was treated with DNase I (ThermoFisher Scientific, EN0525) and reversely transcribed into cDNA by reverse transcriptase (ThermoFisher Scientific, EP0441) . SYBR Green PCR Master Mix (Toyobo, QPK-201) was used in qRT-PCR experiments. The 2 ^-ΔΔCt method was performed to calculate relative expression. Primers are listed in Table 1.

m ⁶A dot blot assay

The m ⁶A dot blot assay was carried out on a Bio-Dot Apparatus (Bio-Rad) as previously described with minor modification. Briefly, total RNA isolated from rapid frozen (by liquid nitrogen) hippocampus tissue (8 weeks male) was quantified using a NanoPhotometer P330 (Implen) , and spotted onto a positive-charged nylon-based membrane (GE Healthcare, RPN303B) . RNA samples were then blocked by 5%skim milk (Amresco, M203) dissolved in blocking buffer (LI-COR, 927-50000) at room temperature for 2 h, and incubated with primary antibody anti-m ⁶A (1: 3000, Abcam, ab151230) at 4 ℃ overnight. RNA samples were next washed by 1×TBST (3×5 min, CWBIO, CW00435) , incubated with secondary antibody IRDye 800CW (1:5000, Odyssey, 926-32211) at room temperature for 2 h, and washed again with 1×TBST (2×5 min) . Images were obtained from ODYSSEY CLx (LI-COR) and analyzed by ImageJ (v1.51K) .

miCLIP-SMARTer-m ⁶A-seq

Small scale single-base resolution m ⁶A methylome detection was carried out following procedures modified from previously report. Briefly, 100 ng mRNAs were isolated from 5 mice (8 weeks male) hippocampus using Dynabeads mRNA Purification Kit (Life Technologies, 61006) and fragmented to ～100 nt using fragmentation reagent (Life Technologies, AM8740) , then incubated with 5 μg anti- m ⁶A antibody (Abcam, ab151230) in 450 μl immunoprecipitation buffer (50 mM Tris, 100 mM NaCl, 0.05%NP-40, adjusted to pH 7.4) under gentle rotation at 4 ℃ for 2 h. The mixture was then transferred into a clear flat-bottom 96-well plate (Corning) on ice, and irradiated three times with 0.15 J/cm ^-2 at 254 nm in a CL-1000 Ultraviolet Crosslinker (UVP) . After irradiation, the mixture was collected and incubated with 50 μl pre-washed Dynabeads Protein A (Life Technologies, 1001D) at 4 ℃ for 2 h. After extensive washing by high-salt buffer (2 times, 50 mM Tris, 1 M NaCl, 1 mM EDTA, 1%NP-40, 0.1%SDS, adjusted to pH 7.4) and immunoprecipitation buffer (2 times) , and dephosphorylation with T4 PNK (NEB, M0201L) at 37 ℃ for 20 min on beads. The RNA was eluted from the beads by proteinase K (Sigma, P2308) treatment at 55 ℃ for 1 h, followed by phenol-chloroform extraction and ethanol precipitation. Purified RNA was subjected to library construction using SMARTer smRNA-Seq Kit for Illumina (Clontech Laboratories, 635030) according to the manufacturer’s instructions and sequenced on Illumina HiSeq X Ten platform.

RNA-sequencing

RNA sequencing samples were prepared according to the instruction of TruSeq RNA Sample Prep Kit (Illumina, FC-122-1001) . Briefly, total RNAs (～5 μg) were extracted from rapid frozen mice hippocampus tissue and used to generate cDNA libraries. All samples were sequenced on Illumina HiSeq X Ten platform. Two replicates were sequenced (each replicate represents one mouse) for each condition.

Protein extraction and Western blot

Total proteins from either mice hippocampus or primary cortical neurons were extracted by N-PER Neuronal Protein Extraction Reagent (ThermoFisher Scientific, 87792) . Pierce Coomassie Protein Assay Kit (ThermoFisher Scientific, 23200) was used to calculate the protein concentration. Protein fraction (～50 μg) was separated by 10%SDS-PAGE and analyzed by immunoblotting with corresponding antibodies, anti-METTL3 (1: 1000, Abcam, ab195352) , anti-beta TUBULIN (1: 2000, Abcam, ab108342) , anti-GAPDH (1: 7500, Proteintech, 60004-1-AP) , anti-c-FOS (1: 1000, Abcam, ab214672) , anti-EGR1 (1: 1000, ThermoFisher Scientific, MA5-15008) , anti-NPAS4 (1: 500, Abcam, ab109984) , anti-ARC (1: 1000, Abcam, ab183183) , and anti-NR4A1 (1: 1000, Abcam, ab109180) . IRDye secondary antibodies were used for protein detection by the LI-COR Odyssey imaging systems (ODYSSEY CLx, LI-COR) . The relative protein levels were analyzed by ImageJ (v1.51K) .

Analysis of miCLIP-m ⁶A-seq data

miCLIP-seq data (paired-end) were analyzed according to preset protocol. Briefly, adaptor sequences were trimmed by Cutadapt (v1.7.1) with parameters: -q 5 -O 5 -m 20. Forward reads were demultiplexed by fastq2collapse. pl (CTK Tool Kit, v1.0.9) and the reverse reads were first transformed to reverse complementary sequences using fastx_reverse_complement (FASTX Toolkit, v0.0.13) then processed in the same way. Next, random barcodes were striped by stripBarcode. pl (CTK Tool Kit, v1.0.9) and attached to the reads headers to facilitate downstream CIMS analysis, then pull the forward and transformed reverse reads of each sample into a single file and align them to the reference genome (mm10, USCS Genome Browser) using BWA (v0.7.12-r1039) with parameters: -n 0.06 -q 35. Cross-linking-induced mutation sites (CIMSs) were identified using CTK Tool Kit (v1.0.9) : uniquely aligned reads were selected using parseAlignment. pl (--map-qual 1 --min-len 18) and PCR duplicates were collapsed using tag2collapse. pl (-EM 30 --seq-error-model alignment) . Mutation sites (insertions, deletions and substitutions) were then identified using joinWrapper. py, and CIMS C→T transitions were specified using CIMS. pl (-n 10) . Only CIMS sites with transition number≥2 (m≥2) and transition to total coverage ratio between 1%and 50% (0.01≤m/k≤0.5) were selected for further analysis. Adenosines positioned 5'adjacent to CIMS sites were identified as m ⁶A sites and annotated by bed2annotation. pl (-dbkey mm10) . Metagene distribution was analyzed using metaPlotR, and motif enrichment analysis was performed using findMotifs. pl (Homer v4.8) .

Analysis of RNA-seq data

Paired-end, adapter-clean reads were first aligned to the reference genome (mm10, USCS Genome Browser) using Tophat2 (v2.1.1) with default parameters. Cufflinks (v2.2.1) was used to assemble uniquely mapped reads into transcripts and estimate respective abundance (FPKM) with default parameters. Differentially expressed genes between samples were identified by using Cuffdiff (2.2.1) with fold change≥2 and q-value≤0.05 as thresholds. Gene ontology (biological process) enrichment analysis was performed using Metascape online service (metascape. org/gp/index. html#/main/step1) .

Cell culture

Primary neurons were isolated from the cortical tissues of E18.5 Mettl3 ^f/f embryos without discrimination of sex. Briefly, brain cortical tissues were dissociated with Neural Tissue Dissociation Kit (Miltenyi, 130092628) following the manufacture’s instruction. Neurons were plated onto Matrigel (Corning, 354227) pre-coated plates (Coring) at a density of 5x10 ⁵ cells/cm ², and cultured with Neurobasal (Gibco, 21103049) supplemented with 2%B-27 (Gibco, 17504044) , 1%GlutaMAX (Gibco, 35050061) , 1%non-essential amino acids solution (Gibco, 11140050) , and 1%penicillin-streptomycin-neomycin antibiotic mixture (Gibco, 15640055) . Cells were maintained under 37 ℃ and 5%CO ₂ conditions, and the culture medium was half-changed every two days. For Mettl3 knockout and rescue experiment, neurons were first infected with adenovirus expressing Cre-GFP (HANBIO, HBAD1016) or GFP (HANBIO, HBAD1009) at DIV 3 (3 days in vitro) to achieve Mettl3 conditional knockout, and infected with AAV2/DJ expressing wildtype Mettl3, mutated Mettl3, or RFP at DIV 5. For overexpressing Mettl3 experiment, neurons were directly infected with AAV2/DJ expressing wildtype Mettl3, mutated Mettl3, or RFP at DIV5. Prior to infection, half of the culture medium was collected, and the neurons were incubated with respective viruses overnight. On the next day, cells were washed and changed to culture medium composed of the collected culture medium prior to virus infection (50%) , and the fresh culture medium (50%) . At DIV 8 to 10, neurons were stimulated with 25 mM KCl (Sigma, P5405) for 1 hour in the incubator, then collected for downstream analysis.

Statistical tests

Results are presented in boxplot (median, 25 ^th and 75 ^th percentiles) with data points plotted inside the box or in bar plots and dot plots as mean±SEM. Statistical analysis and plot drawing were performed using either Prism GraphPad 5 or R (v3.1.3) . Data distribution was presumed to be normal and homoscedastic between groups, but this was not formally tested. Comparison between two groups was analyzed by two-tailed Student’s t-test and comparison between three or more groups was analyzed by one-way ANOVA and Tukey’s Honest Significant Differences (Tukey’s HSD) post hoc test unless otherwise indicated. The statistical tests, exact P values, sample sizes (n) for each experiment are specified in the figure legend.

The formation of long-term memory (LTM) is critical for learning ability and social behaviors of humans and animals, yet its underlying mechanisms are largely unknown. Long-term memory (LTM) , as accumulated with rote learning or experience, is essential for mammalian behavioral adaptation and intelligence development. The transformation from short-term memories to long-term memories requires de novo protein synthesis for synaptic consolidation, of which long term potentiation (LTP) of neurons is considered as one of the major contributors. Although of great importance, the molecular mechanisms regulating LTM formation, particularly at the post-transcriptional level, may remain largely elusive.

The following Examples show that the efficacy of hippocampus-dependent memory consolidation is regulated by METTL3. Depleting METTL3 in mouse hippocampus reduces memory consolidation ability, yet unimpaired learning outcomes can be achieved if adequate training was given or the m ⁶A methyltransferase function of METTL3 was restored. The abundance of METTL3 in wild-type mouse hippocampus is positively correlated with learning efficacy, and overexpression of METTL3 significantly enhances long-term memory consolidation.

Example 1 Knocking out Mettl3 in adult mouse hippocampus does not alter brain anatomical features

Mettl3 ^flox/flox mice were crossed with CaMKIIα-Cre mice to generate forebrain excitatory neuron specific Mettl3 conditional knockout mice (Mettl3 ^flox/flox; CaMKIIα-Cre, hereafter cKO) as shown in FIGs. 1A and 5A. The cKO mice were viable, fertile and developed normally into adulthood with comparable body and brain weights to the control littermates (Mettl3flox/flox, hereafter CTRL) (FIGs. 5B and 5C) . After 8 weeks, the cKO mice had normal brain architecture in terms of brain morphology as well as the numbers and distributions of neurons, astrocytes and microglial cells, and no additional apoptosis, as illustrated in FIGs. 5E-5I. After rotarod test, open field test, elevated plus maze test and Morris water maze test, no difference, between the CTRL and cKO mice in motor coordination, exploratory behavior, anxiety levels, and swimming ability (see FIGs. 6A-6F) , was detected. The cKO mice showed intact short-term memory in new object recognition test (see FIG. 1B) .

Example 2 Depletion of METTL3 in hippocampus resulted in decreased LTM formation ability and prolonged learning period

Morris water maze test was performed to examine the hippocampus-dependent long-term memory (LTM) formation in the cKO mice. The cKO mice took more time than the CTRL group to find the hidden platform in the initial training days, they can still learn gradually. On day 5, the cKO mice reached the platform as fast as the CTRL ones (FIG. 1C) . Consistently, the cKO mice spent significantly less amount of time within the target quadrant than CTRL ones during the first probe test after training day 3, but showed no difference from the cKO mice in the second probe test after training day 5 (FIGs. 1D-1E) . Fear conditioning test was performed. The cKO mice behaved as well as the CTRL ones in contextual freezing evaluation before and 30 minutes after one mild electric shock (FIG. 1F) , suggesting that the cKO mice had normal peripheral pain perception and short-term memory. However, in the context test 24 hours after the first shock, the cKO mice froze only half of the duration as the CTRL mice did, indicating a deficiency in LTM formation (FIG. 1F) . In concert with the water maze test, prolonged training with three mild electric shocks increased the duration of contextual freezing behavior of both CTRL and cKO mice to a similar level (FIG. 1F) . Collectively, these data suggest that depletion of METTL3 in hippocampus resulted in decreased LTM formation ability and prolonged learning period, but did not alter the final training outcome when adequate training was provided.

Example 3 Long-term potentiation (LTP) decrease causes LTM deficiency

To investigate the physiological cause of such phenotype, a whole-cell patch clamp on CA1 pyramidal neurons of both CTRL and cKO mice was performed. The CA1 neurons of cKO mice exhibited normal resting membrane potential, membrane resistance, firing rate, amplitude and duration, as well as response to injected currents (FIGs. 2A and 10A) . The synaptic transmission ability of CA1 pyramidal neurons was tested by measuring the miniature excitatory post-synaptic currents (mEPSCs) and synaptic strength by calculating the input-out relationship (I/O) . No significant change in cKO neurons (FIGs. 2B and 10B) was observed. Paired-pulse facilitation was also normal in cKO neurons, suggesting the cells had normal short-term synaptic plasticity (FIG. 2C) . However, LTP on hippocampal Schaffer collateral pathway exhibited a significant decrease in the slope of field excitatory postsynaptic potential (fEPSP) (FIGs. 2D and 10C) , which was reported to be sufficient to cause LTM deficiency.

Example 4 METTL3-related LTM formation depends upon the m ⁶A methyltransferase function of METTL3

A rescue experiment was performed by stereotaxic injecting adenosine associated virus 2/DJ (AAV2/DJ) carrying mouse Mettl3 cDNA sequence (M3) or Mettl3 cDNA sequence with the methyltransferase domain-mutated (DPPW motif mutated to APPA, M3-Mut) into the dorsal hippocampus of 7-week-old cKO mice. The same age CTRL and cKO mice injected with AAV2/DJ carrying red fluorescent protein were used as the positive and negative controls (CTRL+RFP, cKO+RFP) , respectively. After 2 weeks of recovery, these four groups of mice were examined using Morris water maze test and fear conditioning test. As expected, both the cKO+M3 and cKO+Mut mice synthesized more METTL3 proteins in hippocampus compared to the cKO+RFP group, but increased m ⁶A abundance was only detected in the cKO+M3 mice (FIG. 3A) . Consequently, the cKO+M3 mice performed as good as the CTRL+RFP group in both the water maze and fear conditioning tests, but the cKO+Mut mice showed no improvement as compared with the cKO+RFP group (FIGs. 3B-3D) , indicating that METTL3-related LTM formation depends upon the m ⁶A methyltransferase function of METTL3. Again, after 5 days of water maze training and 3 shocks in the fear conditioning training, all four groups of mice reached the same performance level (FIGs. 3B-3D) , demonstrating the ability of cKO+Mut mice to form LTM after adequate training.

Example 5 The roles of m ⁶A in memory consolidation

A single-base m ⁶A methylome detection was performed by miCLIP-m ⁶A-seq using CTRL mice hippocampus tissues collected at 0 min

30 min, 1 h, and 4 h after one-shock contextual fear conditioning training (FIG. 4A) . A total of 8941, 5995, 6367 and 10853 m ⁶A sites (with an RRACU motif and distributed around stop codon) corresponding to 4424, 3440, 3643, and 5063 expressed genes (referred as m ⁶A-tagged genes below) were identified at the above timepoints, respectively (FIG. 4B) . Among them, about 15-20%expressed genes were timepoint specifically modified by m ⁶A, and 1184 genes were consistently modified at all timepoints. Gene ontology analysis revealed an enrichment of functions in synaptic signaling and neural development among consistently modified genes, an enrichment of functions in membrane-related protein deposition among 30 min and 1 h specifically modified genes, and an enrichment 35 of functions in axon projection among 4 h specific genes (FIG. 4C) , which were in concert with the memory consolidation mechanisms. RNA-seq detected no significant expression difference of the m ⁶A-tagged genes between CTRL and cKO mice hippocampus tissues collected at 0 min

30 min, 1 h, and 4 h after contextual fear conditioning training (FIGs. 4D, 11A and 11B) , indicating that the transcriptional-level regulation of cells in cKO mice hippocampus remains intact.

To investigate the seemingly paradox between the functional defects and mRNA expression consistency among the CTRL and cKO mice, the protein abundance of 6 well-studied immediate-early genes (IEGs) (which should be rapidly activated after learning and are indispensable for LTM formation) was examined using western blot. M ⁶A modification was detected on transcripts of all the 6 genes by MeRIP-qPCR in the CTRL samples (FIGs. 5A and 12) . However, although all these genes showed similar learning induced expression changes in both the CTRL and cKO samples at the RNA level (FIG. 5B) , all of them produced less proteins in cKO mice than in the CTRL ones (FIGs. 5C-5F) , suggesting that the prolonged learning process in cKO mice may due to insufficient protein synthesis in the absence of m ⁶A. To further investigate, the expression of Arc and c-Fos was induced in cultured primary cortical neurons via KCl treatment. Consistent with the in vivo data, the Mettl3-KO neurons produced less ARC and c-FOS proteins than the CTRL ones, but such difference was rescued by introducing wildtype METTL3 into cKO neurons (FIGs. 5C-5E) . Again, METTL3 with mutated methyltransferase domain failed to rescue the protein translation deficiency, indicating the essential roles of m ⁶A in such regulation.

Example 6 Difference in RNA m ⁶A induction in hippocampus is responsible for the individual variation in memory formation efficacy

The above findings suggest that hippocampal METTL3 abundance among individuals may account for the variance of their spatial learning efficacy. Indeed, a moderate positive correlation (r=0.378) between basal hippocampal METTL3 protein abundance and learning efficacy was detected in wildtype mice (8 weeks, male) in Morris water maze test (FIG. 6A) . Mice with more METTL3 tended to spend more time in the target quadrant in the first probe test, but such correlation disappeared after adequate training (probe test II) (FIG. 6A) . To further characterize the relationship between METTL3 abundance and learning efficacy, AAV2/DJ virus carrying either wildtype Mettl3, methyltransferase domain-mutated Mettl3, or RFP was bilaterally injected into the dorsal hippocampus of wildtype mice (WT+M3, WT+Mut, and WT+RFP, respectively) (FIG. 13A) . As expected, overexpressing Mettl3 significantly improved the learning efficacy of mice in both Morris water maze test and one-shock contextual fear conditioning test, but overexpressing Mettl3 with mutated methyltransferase domain had no effect (FIGs. 6B-6D) , suggesting that METTL3 functions through modulating m ⁶A formation. Again, after adequate training (three-shock fear conditioning training) , no behavioral difference was detected among mettl3 overexpression and other groups (FIG. 6D) . Overexpressing Mettl3 in KCl treated primary cortical neurons also significantly enhanced the translation of IEGs Arc and c-Fos, as compared with the wildtype control (FIGs. 6E and 13B) .

As illustrated above, it was demonstrated that METTL3 enhances hippocampus-dependent LTM via promoting the translation efficacy of activity-induced IEGs. In the present disclosure, it is proved that METTL3 mediates LTM formation. In the present disclosure, it is found that knocking out Mettl3 in adult mouse hippocampus does not alter brain anatomical features or short-term memory related electrophysiological activities, such phenomena should be distinguished from developmental stage studies, in which depletion of Mettl3 causes severe defects in whole brain. In accordance with this, the dynamic functional preference of genes modified by m ⁶A at different post-training points (FIG. 4B) also indicate that m ⁶A modification can respond rapidly to stimuli, suggesting that other stimulus related physiological responses may also relate to m ⁶A. Intriguingly, although the absence of Mettl3/m ⁶A results in reduced learning efficacy, equal training outcomes can still be achieved after prolonged water maze training or overdose electric shocks, suggesting a beneficial but not indispensable role of Mettl3/m ⁶A in regulating memory consolidation. Such conclusion may be further supported by the expression evidence of IEGs, as induction of IEGs after training can still be detected in cKO mice at both the mRNA and protein levels, but much weaker at the protein level in cKO mice than in the CTRL ones. Thus, repetitive induction of IEG proteins at a reduced abundance may be able to achieve the required synaptic consolidation effects. The correlation of METTL3 abundance with mouse learning ability suggests that this molecule in hippocampus may be partially responsible for the individual variation in memory formation efficacy, and medicines enhancing Mettl3 expression may improve learning ability and slow down ageing-or disease-related memory loss.

FIGs. 1A-1F illustrate exemplary results indicating postnatal deletion of Mettl3 in hippocampus may prolong the process of LTM consolidation according to some embodiments of the present disclosure. FIG. 1A shows the characterization of Mettl3 conditional knockout in the CA1 region of 8-week male mice brains (scale bars, 100 μm) . FIG. 1B shows the discrimination index of the control (CTRL, Mettl3 ^f/f) and Mettl3 conditional knockout (cKO, Mettl3 ^f/f; CaMKIIα-Cre) mice in novel object recognition test (CTRL, n=13 mice; cKO, n=10 mice) . FIG. 1C shows the results of Morris water maze test on five consecutive training days. FIG. 1D shows the quadrant occupancy of the CTRL and cKO mice in two probe tests ( “a” represents CTRL and “b” represents cKO) . FIG. 1E shows the corresponding representative swimming paths. FIG. 1F shows the freezing behavior before

and 30 min after (short-term) one-shock fear conditioning, and the freezing behavior during contextual test 24 hours after one-shock training or three-shock training. In FIGs. 1D-1F, CTRL, n=14 mice; cKO, n=13 mice. Student’s t-test, *P<0.05, **P<0.01, ***P<0.001, N.S., not significant.

FIGs. 2A-2D illustrate exemplary results indicating electrophysiological tests of Mettl3-depleted hippocampus according to some embodiments of the present disclosure. FIG. 2A shows representative traces and numbers of action potentials responding to stimuli with different intensity in CTRL and cKO CA1 pyramidal neurons (n=10 hippocampal slices from 3 mice per group) . FIG. 2B shows representative traces of mESPCs and distribution of cumulative probability of mEPSCs amplitude and frequency. The insets show the comparison of mean values. FIG. 2C shows paired-pulse ratio at different inter-stimulus intervals in CTRL and cKO groups (n=9 hippocampal slices from 3 mice per group) . FIG. 2D shows field EPSP slope change in CTRL and cKO groups following a single theta-burst stimulation (TBS) . Insets show representative traces at baseline and 1 h after TBS induction (n=9 hippocampal slices from 3 mice per group) . Student’s t-test, N.S., not significant.

FIGs. 3A-3D illustrate exemplary results indicating METTL3 regulates long-term memory formation via its m ⁶A methyltransferase function according to some embodiments of the present disclosure. FIG. 3A shows restoration of METTL3 and m ⁶A in the hippocampus of cKO mice. #1 and #2 represent two biological replicates. FIG. 3B shows re-introducing wildtype Mettl3 (M3) , but not Mettl3 with deficient m ⁶A methyltransferase function (Mut) , to hippocampus rescued the learning delay of cKO mice in Morris water maze test. FIG. 3C shows probe tests of groups in FIG. 3B ( “a” represents CTRL+RFP, “b” represents cKO+M3, “c” represents cKO+Mut, and “d” represents cKO+RFP) . Upper panel, occupancy frequency the target and nontarget quadrants; lower panel, representative swimming paths of the upper panel. In FIGs. 3B and 3C, RFP: injection control; CTRL+RFP, n=10 mice; cKO+M3, n=10 mice; cKO+Mut, n=8 mice; cKO+RFP, n=9 mice. FIG. 3D shows re-introducing wildtype Mettl3 rescues the learning defect of cKO mice in fear-conditioning test (CTRL+RFP, n=10 mice; cKO+M3, n=9 mice; cKO+Mut, n=10 mice; cKO+RFP, n=10 mice) . In FIGs. 3B-3D, ANOVA and Tukey’s HSD post hoc test, *P<0.05, **P<0.01, ***P<0.001, N.S., not significant.

FIGs. 4A-4D illustrate exemplary results indicating m ⁶A methylome is dynamically regulated during memory consolidation. FIG. 4A shows experimental design of sampling strategy. FIG. 4B shows m ⁶A distribution (top panel) , motif (middle panel) and number of m ⁶A-tagged genes (down panel) before and after fear conditioning training. FIG. 4C shows gene ontology (GO) enrichment analysis of common and timepoint specific m ⁶A-tagged genes. Node size is proportionate to related gene numbers, color scales represent term enrichment significance. FIG. 4D shows expression comparison of m ⁶A-tagged genes between CTRL and cKO hippocampus at different timepoints. r refers to Pearson correlation coefficient.

FIGs. 5A-5F illustrate exemplary results indicating m ⁶A promotes the translation of immediate-early genes upon activity induction according to some embodiments of the present disclosure. FIG. 5A shows immediate-early genes (IEGs) are m ⁶A-tagged and are comparably induced by fear conditioning training in hippocampus of both CTRL and cKO mice (FIG. 5B) . FIGs. 5C-5E show translation of IEGs is impaired in cKO mice after training and can be rescued by the m ⁶A methyltransferase activity of METTL3 in Mettl3 ^f/f primary neurons. FIG. 5C shows western blot and FIG. 5D-5E show relative quantification. FIG. 5F shows immunofluorescent image of EGR1 in CA1 region before and after fear conditioning training (1 h and 4 h) . Student’s t-test, *P<0.05, **P<0.01, ***P<0.001, N.S., not significant, in FIGs. 5A and 5C-5E, n=3 replicates, in FIG. 5B n=2 replicates.

FIGs. 6A-6E illustrate exemplary results indicating overexpression of METTL3 enhances long-term memory formation according to some embodiments of the present disclosure. FIG. 6A shows correlation between hippocampal METTL3 level with mice performance in two probe tests. n=20 mice. r, Pearson correlation coefficient. FIGs. 6B-6C show Morris water maze test. FIGs. 6D shows fear conditioning test showing the outperformance learning efficacy of WT+M3 mice vs. WT+Mut and WT+RFP mice in one-shock training but not three-shock training. FIG. 6E shows overexpressing Mettl3 enhanced IEGs translation in primary neurons upon KCl treatment. In FIGs. 6B-6E, Student’s t-test, **P<0.01, ***P<0.001. N.S., not significant, in FIGs. 6B-6D, n=10 mice per group, in FIG. 6E, n=3 replicates.

FIG. 7 illustrates an exemplary proposed model according to some embodiments of the present disclosure. In FIG. 7, METTL3-mediated m ⁶A modification may regulate long-term memory consolidation via promoting the translation efficacy of immediate-early genes in mouse hippocampus. As illustrated, prolonged training may compensate m ⁶A-deficiency induced learning defects, and overexpression of METTL3 may enhance learning efficacy.

FIGs. 8A-8H illustrate exemplary results indicating characterization of brain gross morphology of Mettl3 cKO mice according to some embodiments of the present disclosure. FIG. 8A shows CaMKIIα-Cre-mediated KO of Mettl3 decreases m ⁶A abundance in hippocampus (n=3 replicates) . cKO mice developed normally into adulthood with normal (FIG. 8B) body weight, (FIG. 8C) brain weight, (FIGs. 8D-8G) brain morphology and (FIG. 8H) without observable apoptosis in hippocampus (8 weeks) . Student’s t-test, *P<0.05, **P<0.01, N.S., not significant; in FIGs. 8B-8C, n=8 mice per group.

FIGs. 9A-9F illustrate exemplary results indicating Mettl3 cKO mice show no difference in locomotion, exploration and anxiety as compared to CTRL according to some embodiments of the present disclosure. FIG. 9A shows Rotarod test measures animals’motor coordination (CTRL, n=14 mice; cKO, n=11 mice) . FIG. 9B shows total moved distance within 10 min in an open field arena. FIG. 9C shows duration of mice spent in central zone and representative moving traces (n=10 mice per group) . FIG. 9D shows duration of mice spent in open or closed arms and representative traces (CTRL, n=12 mice; cKO, n=11 mice) . FIG. 9E shows representative heatmaps showing animals’preference for the novel object (solid circle) over the old object (dashed circle) . FIG. 9F shows total swimming distance of mice (CTRL, n=11 mice; cKO, n=10 mice) . Student’s t-test, N.S., not significant.

FIGs. 10A-10C illustrate exemplary results indicating characterization of electrophysiological properties of cKO mice according to some embodiments of the present disclosure. FIG. 10A shows measurements from whole cell recordings of CA1 pyramidal neurons. fAHP, fast after-hyperpolarization; sAHP, slow after-hyperpolarization. FIG. 10B shows input-output curve of fEPSP in responding to different stimulus in CA1 region. FIG. 10C shows slope of fEPSP during the last 10 min of LTP recording. Baseline is measured during the last 10 min before theta-burst stimulation. In FIG. 10A, n=10 brain slices from 3 mice per group. In FIGs. 10B-10C, n=9 brain slices from 3 mice per group. Student’s t-test, ***P<0.001, N.S., not significant.

FIGs. 11A-11B illustrate exemplary results indicating analysis of transcriptomic change during early timepoints after training according to some embodiments of the present disclosure. FIG. 11A shows Volcano plots showing no dramatic transcriptomic abundance change (FPKM) between CTRL and cKO mice at all timepoints. m ⁶A-tagged genes are color-coded, respectively. FIG. 11B shows expression heatmaps of key genes related to synaptic functions between cKO and CTRL mice at respective timepoints (all genes listed are modified by m ⁶A except for Cdk5, which is not identified from miCLIP-m6A-seq) . Two RNA-seq replicates are included in both the CTRL and cKO groups.

FIG. 12 illustrates exemplary results indicating validation of MeRIP-qPCR according to some embodiments of the present disclosure. Positive and negative control of MeRIP-qPCR experiments (related to FIG. 5A) . n=3 replicates.

FIGs. 13A-13B illustrate exemplary results indicating overexpression of Mettl3 in hippocampus or primary neurons according to some embodiments of the present disclosure. FIG. 13A shows overexpression of Mettl3 in mice hippocampus increases m ⁶A abundance. Student’s t-test, **P<0.01, ***P<0.001, N.S., not significant. FIG. 13B shows overexpressing of Mettl3 in primary neurons enhances translation of IEGs (induced by KCl treatment) . n=3 replicates.

It should be noted that the examples described above are merely provided for the purposes of illustration, and not intended to limit the scope of the present disclosure. For persons having ordinary skill in the art, multiple variations and modifications may be made under the teachings of the present disclosure. However, those variations and modifications do not depart from the scope of the present disclosure.

Having thus described the basic concepts, it may be rather apparent to those skilled in the art after reading this detailed disclosure that the foregoing detailed disclosure is intended to be presented by way of example only and is not limiting. Various alterations, improvements, and modifications may occur and are intended to those skilled in the art, though not expressly stated herein. These alterations, improvements, and modifications are intended to be suggested by this disclosure, and are within the spirit and scope of the exemplary embodiments of this disclosure.

Moreover, certain terminology has been used to describe embodiments of the present disclosure. For example, the terms “one embodiment, ” “an embodiment, ” and “some embodiments” mean that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present disclosure. Therefore, it is emphasized and should be appreciated that two or more references to “an embodiment” or “one embodiment” or “an alternative embodiment” in various portions of this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures or characteristics may be combined as suitable in one or more embodiments of the present disclosure.

Furthermore, the recited order of processing elements or sequences, or the use of numbers, letters, or other designations, therefore, is not intended to limit the claimed processes and methods to any order except as may be specified in the claims. Although the above disclosure discusses through various examples what is currently considered to be a variety of useful embodiments of the disclosure, it is to be understood that such detail is solely for that purpose and that the appended claims are not limited to the disclosed embodiments, but, on the contrary, are intended to cover modifications and equivalent arrangements that are within the spirit and scope of the disclosed embodiments. For example, although the implementation of various components described above may be embodied in a hardware device, it may also be implemented as a software-only solution, e.g., an installation on an existing server or mobile device.

Similarly, it should be appreciated that in the foregoing description of embodiments of the present disclosure, various features are sometimes grouped together in a single embodiment, figure, or description thereof to streamline the disclosure aiding in the understanding of one or more of the various embodiments. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed subject matter requires more features than are expressly recited in each claim. Rather, claim subject matter lie in less than all features of a single foregoing disclosed embodiment.

Claims

A method, comprising:

administering, to a subject to improve brain function or enhance learning ability or memory of the subject, a composition including one or more agents that increase METTL3 (N ⁶-adenosine-methyltransferase 70 kDa subunit) potency in at least one body part of the subject.
The method of claim 1, wherein the subject is a human or animal.
The method of any of claims 1-2, wherein the subject is suffering from a learning or memory disorder.
The method of any of claims 1-2, wherein the subject has a learning or memory deficit.
The method of any of claims 1-2, wherein the subject is suffering from agnosia, Alzheimer's disease, amnesia, traumatic brain injury, or dementia.
The method of any of claims 1-2, wherein the subject is mentally healthy.
The method of any of claims 1-6, wherein the at least one body part of the subject includes the brain of the subject.
The method of any of claims 1-6, wherein the at least one body part of the subject includes the hippocampus of the subject.
The method of any of claim 1-8, wherein the one or more agents are configured to increase METTL3 amount in the at least one body part.
The method of claim 9, wherein the one or more agents include a METTL3 peptide.
The method of claim 9, wherein the one or more agents include a Mettl3 cDNA sequence or a fragment of the Mettl3 cDNA sequence.
The method of claim 9, wherein the one or more agents include an engineered carrier vector comprising a Mettl3 cDNA sequence or a fragment of the Mettl3 cDNA sequence.
The method of claim 9, wherein the one or more agents include an engineered virus comprising Mettl3 cDNA sequence or a fragment of the Mettl3 cDNA sequence.
The method of claim 13, wherein the virus includes adenosine associated virus, adenosine virus, lentivirus, or sendai virus.
The method of claim 9, wherein the one or more agents are configured to increase METTL3 expression by stimulating a positive factor that enhances METTL3 expression.
The method of claim 9, wherein the one or more agents are configured to increase METTL3 expression by inhibiting a negative factor that reduces METTL3 expression.
The method of claim 16, wherein the one or more agents include an antibody.
The method of any of claims 1-8, wherein the one or more agents are configured to stimulate METTL3 activity in the at least one body part.
The method of claim 18, wherein the one or more agents include a METTL3 agonist.
The method of claim 18, wherein the one or more agents are configured to increase METTL3 activity by stimulating a positive factor that enhances METTL3 activity.
The method of claim 9, wherein the one or more agents are configured to increase METTL3 activity by inhibiting a negative factor that reduces METTL3 activity.
The method of any of claims 1-21, wherein administering to a subject a composition comprises administering the composition to the skin of the subject.
The method of any of claims 1-21, wherein administering to a subject a composition comprises injecting the composition to the subject.
The method of any of claims 1-21, wherein administering to a subject a composition comprises administering orally the composition to the subject.
The method of any of claims 1-21, wherein the composition is configured as a suppository.
A method, comprising:

administering, to a subject to enhance learning ability of the subject, a composition including one or more agents that increase METTL3 (N ⁶-adenosine-methyltransferase 70 kDa subunit) potency in at least one body part of the subject.
A method, comprising:

administering, to a subject to enhance memory of the subject, a composition including one or more agents that increase METTL3 (N ⁶-adenosine-methyltransferase 70 kDa subunit) potency in at least one body part of the subject.
A method, comprising:

administering, to a subject to enhance long term memory consolidation of the subject, a composition including one or more agents that increase METTL3 (N ⁶-adenosine-methyltransferase 70 kDa subunit) potency in at least one body part of the subject.
A method, comprising:

administering, to a subject to enhance long term memory consolidation of the subject, a composition including one or more agents that increase METTL3 (N ⁶-adenosine-methyltransferase 70 kDa subunit) potency in the hippocampus of the subject.
A method, comprising:

administering, to a subject to improve brain function of the subject suffering from a mental disorder, a composition including one or more agents that increase METTL3 (N ⁶-adenosine-methyltransferase 70 kDa subunit) potency in the hippocampus of the subject.
A method, comprising:

administering, to a subject to enhance long term memory consolidation of the subject suffering from a memory deficit, a composition including one or more agents that increase METTL3 (N ⁶-adenosine-methyltransferase 70 kDa subunit) potency in the hippocampus of the subject.
A method, comprising:

administering, to a subject to enhance long term memory consolidation of the subject that is not suffering from memory deficit, a composition including one or more agents that increase METTL3 (N ⁶-adenosine-methyltransferase 70 kDa subunit) potency in the hippocampus of the subject.
A method, comprising:

administering, to a subject to improve brain function or enhance learning ability or memory of the subject, a composition including one or more agents that increase N ⁶-methyladenosine (m ⁶A) abundance in at least one body part of the subject.
A method for assessing learning ability or memory ability of a subject comprising:

(a) assessing the level of an N ⁶-methyladenosine (m ⁶A) -related protein in at least one body part of the subject;

(b) comparing the level of m ⁶A or the m ⁶A-related protein to a standard level; and

(c) determining the learning ability or memory ability of the subject based on the comparison of (b) .
The method of claim 34, wherein the m ⁶A-related protein is the METTL3 protein.
The method of claim 34, wherein the at least one body part of the subject includes the hippocampus of the subject.
The method of claim 34, wherein the standard level is obtained by assessing the level of the m ⁶A-related protein in the at least one body part of subjects in a control group.
A composition configured to improve brain function or enhance learning ability or memory of a subject, comprising one or more agents that increase METTL3 (N ⁶-adenosine-methyltransferase 70 kDa subunit) potency in at least one body part of the subject.
The composition of claim 38, wherein the subject is a human or animal.
The composition of any of claims 38-39, wherein the subject is suffering from a learning or memory disorder.
The composition of any of claims 38-39, wherein the subject has a learning or memory deficit.
The composition of any of claims 38-39, wherein the subject is suffering from agnosia, Alzheimer's disease, amnesia, traumatic brain injury, or dementia.
The composition of any of claims 38-39, wherein the subject is mentally healthy.
The composition of any of claims 38-43, wherein the at least one body part of the subject includes the brain of the subject.
The composition of any of claims 38-43, wherein the at least one body part of the subject includes the hippocampus of the subject.
The composition of any of claim 38-45, wherein the one or more agents are configured to increase METTL3 amount in the at least one body part.
The composition of claim 46, wherein the one or more agents include a METTL3 peptide.
The composition of claim 46, wherein the one or more agents include a Mettl3 cDNA sequence or a fragment of the Mettl3 cDNA sequence.
The composition of claim 46, wherein the one or more agents include an engineered carrier vector comprising Mettl3 cDNA sequence or a fragment of the Mettl3 cDNA sequence.
The composition of claim 46, wherein the one or more agents include an engineered virus comprising Mettl3 cDNA sequence or a fragment of the Mettl3 cDNA sequence.
The composition of claim 50, wherein the virus includes adenosine associated virus, adenosine virus, lentivirus, or sendai virus.
The composition of claim 46, wherein the one or more agents are configured to increase METTL3 expression by stimulating a positive factor that enhances METTL3 expression.
The composition of claim 46, wherein the one or more agents are configured to increase METTL3 expression by inhibiting a negative factor that reduces METTL3 expression.
The composition of claim 53, wherein the one or more agents include an antibody.
The composition of any of claims 38-45, wherein the one or more agents are configured to stimulate METTL3 activity in the at least one body part.
The composition of claim 55, wherein the one or more agents include a METTL3 agonist.
The composition of claim 55, wherein the one or more agents are configured to increase METTL3 activity by stimulating a positive factor that enhances METTL3 activity.
The composition of claim 46, wherein the one or more agents are configured to increase METTL3 activity by inhibiting a negative factor that reduces METTL3 activity.