METHODS FOR IDENTIFYING COMPOUNDS FOR MOTION SICKNESS, VERTIGO AND OTHER DISORDERS RELATED TO BALANCE AND THE PERCEPTION OF GRAVITY

Abstract: The present invention provides a method of identifying a compound that modulates a mammalian vestibular system. The method consists of administering a test compound to an invertebrate, and measuring a geotactic behavior of the invertebrate, where a compound tht modulates the geotactic behavior of said invertebrate is characterized as a compound that modulates a mammalian vestibular system. The invention also provides a method of identifying a gene that modulates a mammalian vestibular system consisting of obtaining a first and a second strain of an invertebrate; subjecting the first and second invertebrate strains to conditions in which the first strain exhibits a geotactic behavior different than a geotactic behavior exhibited by the second strain; measuring gene expression levels in the first and second strains, and identifying one or more genes that are differentially expressed in the first strain relative to the second strain, whereby a mammalian gene having substantially the same nucleic acid sequence as the one or more differentially expressed genes modulates the mammalian vestibular system.

Description: METHODS FOR IDENTIFYING COMPOUNDS FOR MOTION SICKNESS, VERTIGO AND OTHER DISORDERS RELATED TO BALANCE AND THE PERCEPTION OF GRAVITY BACKGROUND OF THE INVENTION Motion sickness is a condition produced by road, sea, air, or space travel, or by interacting with virtual environments. It is caused by the effect of any pronounced movement on the organ of balance in the inner ear or by sensory conflict about body motion as perceived by different receptors (visual, vestibular, and body proprioceptors) . Symptoms may include headache, excessive sweating and salivation, loss of appetite, malaise, nausea, vomiting, gastrointestinal disturbances and fatigue. Vertigo is the illusion that one's surroundings or self are spinning, either horizontally or vertically, resulting from a disturbance of the semicircular canals in the inner ear or nerve tracts leading from them. It can be induced by motion, zero gravity or disease, and may be accompanied by vomiting, ringing in the ears and unsteadiness. Travel related motion sickness is experienced by approximately 1% of air travelers and can be as high as 100% of ocean travelers on heavy seas. Children between the ages of 3 and 12 are the most susceptible. 50% of astronauts experience "space motion sickness" during space travel. While a source of discomfort, motion sickness and vertigo can also result in impaired performance by crew members on ships, planes or spacecraft, by drivers suffering from circulatory ailments, or by users of computer-based virtual environments . Currently available drugs to treat motion sickness and vertigo produce a variety of undesirable side effects, some producing drowsiness, blurred vision, impaired reaction time and pattern recognition, others negatively affecting mood and sleep. The genes that play important roles in the proper functioning of the vestibular system remain largely uncharacterized. Identification of such genes can provide methods for screening individuals with genetic susceptibility to motion sickness or vertigo and can also provide targets for developing new therapeutic agents that specifically modulate the expression or activity of genes associated with motion sickness or vertigo. Unfortunately, identification of such genes in mammals can be difficult and time consuming. Therefore, there is a need to identify drugs that alleviate motion sickness and vertigo without undesirable side effects. There also exists a need to identify genes whose expression or activity is associated with conditions such as motion sickness or vertigo. The present invention satisfies these needs and provides related advantages as well. SUMMARY OF THE INVENTION The present invention provides a method of identifying a compound that modulates a mammalian vestibular system. The method consists of administering a test compound to an invertebrate, andmeasuring a geotactic behavior of the invertebrate, where a compound that modulates the geotactic behavior of said invertebrate is characterized as a compound that modulates a mammalian vestibular system. The invention also provides a method of identifying a gene that modulates a mammalian vestibular system consisting of obtaining a first and a second strain of an invertebrate; subjecting the first and second invertebrate strains to conditions in which the first strain exhibits a geotactic behavior different than a geotactic behavior exhibited by the second strain; measuring gene expression levels in the first and second strains, and identifying one or more genes that are differentially expressed in the first strain relative to the second strain, whereby a mammalian gene having substantially the same nucleic acid sequence as the one or more differentially expressed genes modulates the mammalian vestibular system. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a schematic of the geotaxis maze used in measuring geotactic scores of Drosophila . DETAILED DESCRIPTION OF THE INVENTION The present invention provides methods of rapidly and efficiently identifying compounds that modulate a mammalian vestibular system, including compounds that decrease dizziness or nausea, or increase balance. The compounds identified by the methods of the invention can be used to treat individuals suffering from motion sickness, vertigo, or other graviperceptive disorders. The present invention also provides mammalian genes that modulate a mammalian vestibular system. A compound identified by the method of the invention can act to modulate the activity or expression of a mammalian gene of the invention. Genetic and molecular studies of perception and response to gravity have not been extensively pursued in multi-cell organisms. As a result, little knowledge exists regarding the molecules that play important roles in perception of gravity and motion. There has been no indication that the manner in which mammals perceive gravity resembles the manner in which invertebrates perceive gravity or that the relative genetic simplicity of invertebrates compared to mammals provides networks of genes controlling graviperceptive behavior in invertebrates that are similar to those operating in mammals. In fact, invertebrates have been shown to have dissimilar pharmaclolgical responses compared to mammals within the same class of receptors. Thus, the use of invertebrates to test compounds affecting mammalian behaviors including, for example, graviperception also has not been pursued. The methods and compounds disclosed herein are based on the discovery that administration of a compound used for treating motion sickness in humans can be effective in changing geotactic behavior of invertebrates and that the network of genes controlling the mammalian vestibular system is similar to the network of genes controlling geotactic behavior of invertebrates. The invention provides a method of identifying a compound that modulates a mammalian vestibular system. The method consists of administering a test compound to an invertebrate and measuring a geotactic behavior of the invertebrate. A candidate compound that modulates the geotactic behavior of the invertebrate is characterized as a compound that modulates a mammalian vestibular system. The methods of the invention provide a means to identify a compound that modulates a mammalian vestibular system because the methods are based on screening geotactic behavior of invertebrates which is a natural system that performs a similar function. Thus, the methods provide for screening compounds in a context similar to the context of the mammalian vestibular system. Additionally, compounds that modulate a mammalian system to various degrees can be identified by the methods of the invention because strains of invertebrates that have naturally evolved different geotactic behaviors and degrees of response can be used with the methods of the invention. According to the methods of the invention, changes in expression of one or more representative genes in a network of genes can be associated with changes in geotactic behavior of an invertebrate to identify compounds that modulate the mammalian vestibular system. Representative genes can include one gene, a set of all genes whose expression changes upon modulation of the mammalian vestibular system, or any subset of genes thereof. The methods of the invention can be used to identify compounds that modulate a mammalian vestibular system by identifying the effects of a compound on a subset of genes involved in the geotactic behavior of invertebrates because the change detected in the subset of genes occurs in the context of a natural network of genes controlling geotactic behavior. The invention provides a method of identifying a compound that modulates a mammalian vestibular system. The method consists of (a) administering a test compound to an invertebrate, and (b) measuring a geotactic behavior of the invertebrate, a compound that modulates the geotactic behavior of the invertebrate is characterized as a compound that modulates a mammalian vestibular system. The invention also provides a method of identifying a compound that modulates a mammalian vestibular system. The method consists of (a) administering a test compound to a test invertebrate; (b) measuring gene expression levels in the test invertebrate; (c) comparing an expression level of one or more genes in the test invertebrate relative to an expression level of one or more genes in a reference invertebrate, wherein a compound that has the effect of modulating the expression level of one or more genes associated with invertebrate geotactic behavior in the test invertebrate relative to the reference invertebrate is characterized as a compound that modulates the mammalian vestibular system. The invention also provides a method of identifying a compound that modulates a mammalian vestibular system. The method consists of (a) administering a test compound to a test invertebrate; (b) measuring gene expression levels in the test invertebrate, and (c) comparing the expression level of one or more genes in the first invertebrate relative to a second invertebrate, wherein a compound that modulates the expression profile of one or more genes comprising a sequence selected from the group consisting of SEQ ID NOS: 1-261 in the first invertebrate relative to the second invertebrate is characterized as a compound that modulates the mammalian vestibular system. As used herein, the term "modulate" refers to an increase, decrease or alteration. The term can be used to indicate an increase, decrease or alteration of a level, activity or function characteristic of a behavior, organ, protein, or other detectable phenomenon. For example, a mammalian vestibular system can be modulated by a compound that increases or decreases graviperception, increases or decreases neuronal response to a graviperceptive signal, and the like. As used herein, the term "compound" as used in regard to modulating invertebrate geotaxis, a mammalian vestibular system, or protein expression or activity, refers to an inorganic or organic molecule such as a drug; a peptide, or a variant or modified peptide or a peptide-like molecule such as a peptidomimetic or peptoid; or a protein such as an antibody, a growth factor, or cytokine, or a fragment thereof such as an Fv, Fd or Fab fragment of an antibody, which contains a binding domain; or a nucleic acid or chemically modified nucleic acid such as an antisense nucleic acid; or a carbohydrate or lipid. Methods of determining compounds useful for modulating invertebrate geotaxis, a mammalian vestibular system, or protein expression or activity are provided herein, and include administering a compound to an invertebrate and identifying whether the compound modulates invertebrate geotaxis, administering a compound to an invertebrate or invertebrate cell culture and identifying whether the compound modulates expression of one or more genes associated with invertebrate geotaxis, and administering a compound to a mammal or mammalian cell culture and identifying compounds that modulate the expression or activity of a protein that modulates the mammalian vestibular system. If desired, a candidate compound can be combined with, or dissolved in, an agent that facilitates uptake of the compound by the invertebrate, such as an organic solvent, for example, DMSO or ethanol; or an aqueous solvent, for example, water or a buffered aqueous solution; or food. A compound identified in the method of the invention modulates a mammalian vestibular system and also modulates geotactic behavior of an invertebrate. A compound that modulates invertebrate geotactic behavior can, for example, increase or decrease a geotactic behavior. Additionally, a compound can increase or decrease a first geotactic behavior while decreasing or increasing, respectively, a second geotactic behavior. For example, a compound can increase geotactic behavior in response to light, while decreasing geotactic behavior in response to heat or humidity. A compound that modulates the activity or expression of a protein can, for example, increase or decrease the expression level or activity of a protein, or influence both expression and activity. For example, a compound can increase the activity but decreases the expression of a protein, as in the case of increased activity of a transcription factor that auto-regulates by feedback inhibition. As described in the present invention, a compound that modulates invertebrate geotaxis can also modulate a mammalian vestibular system. Accordingly, a compound that modulates invertebrate geotaxis can increase or decrease the sensitivity of a mammalian vestibular system. For example, a compound that increases negative geotaxis in an invertebrate can decrease the sensitivity of a mammalian vestibular system. As used herein, the term "mammalian vestibular system" refers to the organ of the inner ear of a mammal containing semicircular ducts and the nerve fibers extending therefrom. The nerve fibers can extend from the inner ear to the central parts of the brain and include, for example, the vestibular nuclei, trochlear nucleus, oculomotor nucleus, abducens nucleus, and vestibulospinal tracts. Typically, a mammalian vestibular system is used to maintain balance, perceive motion and perceive orientation relative to a force vector such as gravity or a physical force such as change in velocity or direction. A mammalian vestibular system can provide signals to the brain that result in graviperceptive disorders. As used herein, a "graviperceptive disorder" refers to any condition that disturbs normal perception of gravity, motion or orientation. A graviperceptive disorder can have genetic or familial basis or can be induced by sickness or other physical conditions such as high blood pressure, or can be brought about by motion, changes in amplitude or direction of a gravitational or physical force, or changes in orientation. Exemplary graviperceptive disorders include, but are not limited to, labyrinthitis, Meniere's disease, motion sickness, vertigo, acoustic neuroma, multiple sclerosis, syphilis, trauma, infection of the middle ear, exposure to ototoxic agents, epilepsy and the like. A graviperceptive disorder is characterized by one or more symptoms such as dizziness, nausea, headache, excessive sweating and salivation, loss of appetite, malaise, gastrointestinal disturbances and fatigue. A variety of graviperceptive disorders in humans are known in the art and are described in, for example, Brandt, Vertigo: Its Multisensory Syndromes, 2 nd Ed., Springer Verlag (1999) . Mammals are understood to refer to members of the class mammalia, and particularly include placental mammals such as sheep, goats, cows, horses, pigs, dogs, cats, rats, mice, primates, humans and the like. Modulation of a mammalian vestibular system can decrease or increase the sensitivity of a mammalian vestibular system, influencing the ability of an individual to maintain balance, perceive motion or perceive orientation, and can also result in, for example, a decrease in the symptoms associated with a graviperceptive disorder such as motion sickness, vertigo, labyrinthitis, Meniere's disease, acoustic neuroma, multiple sclerosis, syphilis, trauma, infection of the middle ear, exposure to ototoxic agents, epilepsy and the like. The term "sensitivity" when used in terms of a mammalian vestibular system refers to the responsiveness of semicircular ducts in sensing motion or orientation or the responsiveness in signaling of semicircular ducts or neurons connected thereto. Such sensitivity can influence symptoms of a graviperceptive disorder such as motion sickness, vertigo, labyrinthitis, Meniere's disease, acoustic neuroma, multiple sclerosis, syphilis, trauma, infection of the middle ear, exposure to ototoxic agents and epilepsy. Typically, decreased sensitivity of a mammalian vestibular system will result in a decrease in symptoms associated with a graviperceptive disorder. A mammalian vestibular system can be modulated by a gene whose expression increases or decreases graviperception, increases or decreases nueronal response to a graviperceptive signal, and the like. In accordance with the present invention, such a gene comprises a nucleic acid sequence substantially the same as an invertebrate gene which modulates invertebrate geotactic behavior. Examples of such genes are PROX1, comprising substantially the same sequence as SEQ ID NO: 15, mammalian tectorin-α, comprising substantially the same sequence as SEQ ID NO: 233; mammalian glycoprotein 330, comprising substantially the same sequence as SEQ ID NO: 108; mammalian protein inhibitor of nNOS, comprising substantially the same sequence as SEQ ID NO: 117; mammalian synaptic vesicle transporter, comprising substantially the same sequence as SEQ ID NO: 250; mammalian actin-binding double-zinc-finger protein, comprising substantially the same sequence as SEQ ID NO: 21; mammalian spinocerebellar ataxia type 2 protein, comprising substantially the same sequence as SEQ ID NO:l; mammalian APP-binding protein, comprising substantially the same sequence as SEQ ID NO: 225; and the like. Further examples are mammalian genes substantially the same as genes containing the nucleic acid sequences of SEQ ID NOS.1-261. The term "geotactic behavior" or "geotaxis" of an invertebrate refer to the behavioral response of an invertebrate to perception of a force vector such as gravity, a visual stimulus or a combination of the two. Geotactic behavior can be manifested by crawling, walking or flying in a specific direction and/or orientation in response to a force vector such as gravity. For example, an invertebrate having a walking pattern characterized as negative geotactic behavior walks in opposition to the force vector, or "upward." Conversely positive geotactic behavior is displayed by an invertebrate which walks in the same direction as the force vector, or "downward." As another example, the orientation of an invertebrate in flight with respect to a force vector, such as, upright, upside-down and the like, is a geotactic behavior. Wild type geotactic behavior refers to a geotactic behavior in an invertebrate which has not been selected for positive or negative geotactic behavior, abnormal flight behavior or other geotactic variant behavior. Exemplary wild type geotactic behavior can be manifest by an equal likelihood of a specific invertebrate to walk against a force vector "upward" as the likelihood of walking with the force vector "downward." Therefore, wild type geotactic behavior can result an invertebrate exhibiting, on average, neither positive nor negative geotactic behavior. Methods for determining geotactic behavior are disclosed herein and are well known in the art, as exemplified in the publications by Horn, "Gravity" in Comprehensive Insect Physiology biochemistry and Pharmacology Vol 6, Pergamon Press (1985) and Schwartzkopff, "Mechanoreception" in The Physiology of Insecta Academic Press (1974), which are incorporated herein by reference. These methods include monitoring the crawling direction of an invertebrate with respect to gravity, monitoring the static orientation of an invertebrate with respect to gravity and monitoring the orientation of flight with respect to gravity. An exemplary apparatus for measuring the crawling direction of an insect is provided in Example I. The modulation of invertebrate geotactic behavior results in increased geotactic behavior, decreased geotactic behavior, or otherwise altering a behavioral response in reaction to a force vector, such as altering flying behavior by, for example, attempting to fly upside-down. As used herein, "increased geotactic behavior" refers to a change from negative to positive geotactic behavior, a lessened extent of negative geotactic behavior, or an increased extent of positive geotactic behavior. Correspondingly, "decreased geotactic behavior" refers to an change from positive to negative geotactic behavior, a lessened extent of positive geotactic behavior, or an increased extent of negative geotactic behavior. Invertebrates are understood to refer to members of the division invertebrata . As disclosed herein, Drosophila melanogaster is an example of an invertebrate that exhibits geotactic behavior that can be measured. Those skilled in the art understand that other Drosophila species are also likely to exhibit similar geotactic behavior and express genes associated with geotactic behavior, including D. simulans , D. virilis , D. pseudoobscura D. funebris , D. immigrans , D. repleta , D. affinis , D. sal tans , D. sulphurigaster albostriga ta and D . nasuta albomicans . Likewise, other flies, including, sand flies, mayflies, blowflies, flesh flies, face flies, houseflies, screw worm-flies, stable flies, mosquitos, northern cattle grub, and the like will also exhibit geotactic behavior and express genes associated with geotactic behavior. Furthermore, insects other than flies can also exhibit geotactic behavior and express genes associated with geotactic behavior. For example, the invention can also be practiced with insects such as cockroaches, honeybees, wasps, termites, grasshoppers, moths, butterflies, fleas, lice, boll weevils, beetles, Apis mellifera , A . florea , A. cerana , Tenebrio moli tor, Bombus terrestris, B . lapidari us, and members of Hydrocorisae . Arthropods other than insects also can exhibit geotactic behavior and express genes associated with geotactic behavior. For example, the invention can also be practiced using arthropods such as scorpions, spiders, mites, crustaceans, centipedes and millipedes. Due to the high degree of genetic similarity across invertebrate species, invertebrates other than arthropods, such as flatworms, nematodes (e.g. C. elegans) , mollusks (e.g. Aplysia or Hermissenda ) , echinoderms and annelids will exhibit geotactic behavior and express genes associated with geotactic behavior, and can be used in the methods of the invention. Those skilled in the art can determine, using the assays described herein, whether a particular invertebrate exhibits geotactic behavior and expresses genes associated with geotactic behavior and, therefore, would be applicable for use in the methods of the invention. The choice of invertebrate will also depend on additional factors, for example, the availability of the invertebrates, the normal activity levels of the invertebrates, the availability of molecular probes for genes associated with geotactic behavior, the number of invertebrates and compounds one intends to use, the ease and cost of maintaining the invertebrates in a laboratory setting, the method of administering and type of compounds being tested, and the particular property being evaluated. Those skilled in the art can evaluate these factors in determining an appropriate invertebrate to use in the screening methods. For example, if it is desired to evaluate gene expression in the methods of the invention, an invertebrate that is genetically well-characterized, such that homologs of genes associated with geotactic behavior are known or can be readily determined, can be used. Thus, appropriate invertebrates in which to evaluate gene expression can include, for example, Drosophila and C. elegans . If it desired to evaluate behavioral properties in the methods of the invention, an invertebrate that exhibits one or more geotactic behaviors, such as fruit flies, cockroaches, honeybees, wasps, moths, mosquitos, scorpions, and the like, can be used. As used herein, a "strain" refers to a population of organisms of a species having at least one similar phenotype, typically a geotactic phenotype. This population of organisms can have either identical or a somewhat heterogeneous genetic makeup, although heterogeneous populations typically contain individuals that are homozygous for one or more chromosomes. For example, a population of organisms having a similar phenotype can be a population of organisms of a species sharing a similar genetic origin as the result of either being isolated from a particular geographic area, sharing particular chromosomes or alleles, or having been bred for multiple generations for a particular phenotype. The term "substantially the same" as used herein in reference to the relationship between a mammalian gene and an invertebrate gene refers to a mammalian nucleic acid or corresponding amino acid sequence that has a high degree of homology to an invertebrate nucleic acid or corresponding amino acid sequence and retains at least one function specific to the invertebrate nucleic acid or corresponding amino acid sequence. In the case of a nucleotide sequence, a first nucleic acid that is substantially the same as a second nucleic acid can selectively hybridize to a sequence complementary to the second nucleic acid under moderately stringent conditions or under highly stringent conditions. Therefore, a first nucleic acid molecule having substantially the same sequence compared to a second nucleic acid sequence can include, for example, one or more additions, deletions or substitutions with respect to the second sequence so long as it can selectively hybridize to a complement of that sequence. In the case of an amino acid sequence, a first amino acid sequence that is substantially the same as a second amino acid sequence can contain minor modifications with respect to the second amino acid sequence, so long as the polypeptide containing the first amino acid sequence retains one or more functional activities exhibited by the whole polypeptide containing the second amino acid sequence. Typically, a substantial similarity is represented by at least about 20% identity between mammalian and invertebrate sequences; mammalian and invertebrate sequences that are substantially the same can also share at least about 30% identity, at least about 40% identity, at least about 50% identity, at least about 60% identity, at least about 70% identity, at least about 80% identity, at least about 90% identity, at least about 95% identity, at least about 97% identity, or at least about 99% identity over the length of the two sequences being compared. Those skilled in the art know that two or more polypeptides having low overall sequence similarity can be substantially similar if the polypeptides have similar domains with substantial sequence similarity. For example, polypeptides having 20% overall identity can be substantially similar if the polypeptides contain one or more domains of substantial similarity. A larger number of similar domains between two or more polypeptides correlates with increased similarity. Therefore, substantial similarity can be identified according to sequence identity within similar domains of two or more polypeptides. Examples of methods for determining substantial similarity using sequence identity or a combination of sequence identity and similarity in domain structure are described below. The appropriate function to be retained will depend on the desired use of the nucleic acid molecule. For example, a mammalian gene substantially the same as an invertebrate gene associated with geotactic behavior can be a polypeptide having substantially the same immunogenicity, antigenicity, enzymatic activity, binding activity, or other biological property, including invertebrate geotactic behavior modulating activity which will correspond to mammalian vestibular system modulating activity, as the polypeptide encoded by the invertebrate nucleic acid molecule. Methods for determining that two sequences are substantially the same are well known in the art. For example, one method for determining if two sequences are substantially the same is BLAST, Basic Local Alignment Search Tool, which can be used according to default parameters as described by ' Tatiana et al., FEMS Microbiol Lett. 174:247-250 (1999) or on the National Center for Biotechnology Information web page at ncbi.nlm.gov/BLAST/. BLAST is a set of similarity search programs designed to examine all available sequence databases and can function to search for similarities in protein or nucleotide sequences. A BLAST search provides search scores that have a well-defined statistical interpretation. Furthermore, BLAST uses a heuristic algorithm that seeks local alignments and is therefore able to detect relationships among sequences which share only isolated regions of similarity including , for example, protein domains (Altschul et al., J. Mol. Biol. 215:403-410 (1990)). In addition to the originally described BLAST (Altschul et al., supra , 1990), modifications to the algorithm have been made (Altschul et al., Nucleic Acids Res. 25:3389-3402 (1997)). One modification is Gapped BLAST, which allows gaps, either insertions or deletions, to be introduced into alignments. Allowing gaps in alignments tends to reflect biologic relationships more closely. For example, gapped BLAST can be used to identify sequence identity within similar domains of two or more proteins. A second modification is PSI-BLAST, which is a sensitive way to search for sequence homologs . PSI-BLAST performs an initial Gapped BLAST search and uses information from any significant alignments to construct a position-specific score matrix, which replaces the query sequence for the next round of database searching. A PSI-BLAST search is often more sensitive to weak but biologically relevant sequence similarities . A second resource that can be used to determine if two sequences are substantially the same is PROSITE, available on the world wide web at ExPASy . PROSITE is a method of determining the function of uncharacterized proteins translated from genomic or cDNA sequences (Bairoch et al., Nucleic Acids Res. 25:217-221 (1997)). PROSITE consists of a database of biologically significant sites and patterns that can be used to identify which known family of proteins, if any, the new sequence belongs. In some cases, the sequence of an unknown protein is too distantly related to any protein of known structure to detect similarity by overall sequence alignment. However, a protein that is substantially the same as another protein can be identified by the occurrence in its sequence of a particular cluster of amino acid residues, which can be called a pattern, motif, signature or fingerprint, that is substantially the same as a particular cluster of amino acid residues in the other protein including, for example, those found in similar domains. PROSITE uses a computer algorithm to search for motifs that identify proteins as family members. PROSITE also maintains a compilation of previously identified motifs, which can be used to determine if a newly identified protein is a member of a known protein family. The term "moderately stringent conditions, " as used here is intended to refer to hybridization conditions equivalent to hybridization of filter-bound nucleic acid in 50% formamide, 5 X Denhart ' s solution, 5 X SSPE, 0.2% SDS at 42°C, followed by washing in 0.2 X SSPE, 0.2% SDS, at 50°. In contrast, "highly stringent conditions" are conditions equivalent to hybridization of filter-bound nucleic acid in 50% formamide, 5 X Denhart ' s solution, 5 X SSPE, 0.2% SDS at 42°C, followed by washing in 0.2 X SSPE, 0.2% SDS, at 65°. Other suitable moderately stringent and highly stringent hybridization buffers and conditions are well known to those of skill in the art and are described, for example, in Sambrook et al., Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory, New York (1992) and in Ausubel et al., Current Protocols in Molecular Biology, John Wiley and Sons, Baltimore, MD (1998). The sequences of corresponding genes associated with geotactic behavior of desired species can be determined by methods well known in the art, which include methods such as PCR or screening genomic, cDNA or expression libraries derived from that species. A modification of a nucleic acid molecule can also include substitutions that do not change the encoded amino acid sequence due to the degeneracy of the genetic code. Such modifications can correspond to variations that are made deliberately, or which occur as mutations during nucleic acid replication. Additionally, a modification of a nucleic acid molecule can correspond to a splice variant form of the recited sequence. Additionally, a fragment of a mammalian gene can be substantially the same as an invertebrate gene or a fragment of an invertebrate gene. As used herein, a "fragment" of a gene refers to a portion of a gene that retains at least one biological function of the wild type gene. A mammalian gene can be substantially the same as an invertebrate gene, for example, when one of several domains encoded by a mammalian gene corresponds to a domain encoded by an invertebrate protein. Such a fragment typically is encoded by at least 30 nucleotides, and the mammalian and invertebrate genes encoding that fragment share at least about 50% identity, at least about 60% identity, at least about 70% identity, at least about 80% identity, at least about 90% identity, at least about 95% identity or at least about 98% identity. Methods for determining that a fragment of a mammalian gene is substantially the same as an invertebrate gene or a fragment of an invertebrate gene include those described above for comparing mammalian and invertebrate genes. Such a fragment can be encoded by 30 or more nucleotides, for example, 45 or more nucleotides, 60 or more nucleotides, 90 or more nucleotides, 150 or more nucleotides, 210 or more nucleotides, or 300 or more nucleotides . Biological functions retained by a fragment can include the ability to modulate a mammalian vestibular system, the ability to modulate invertebrate geotaxis, the ability to bind an antibody that binds to a full-length protein which comprises the fragment, or an enzymatic or binding activity characteristic of the full length protein. For example, a 30 amino acid fragment of prospero interacts with miranda for subcellular localization as described in Hirata et al. Nature 377:627-630 (1995) and peptides corresponding to 30 amino acid domains of CaMKII and PKC inhibit the respective full length enzymes as described in Kane et al., Neuron 18:307-314 (1997), Broughton et al., J. Cell. Biochem. 62:484-494 (1996), Broughton et al., J. Cell. Biochem. 60:584-600 (1996) and Griffith et al., Neuron 10:501-509 (1993) . The term "administering" a compound refers to any method of delivering a compound to an invertebrate or mammalian subject in such a way that invertebrate geotaxis or a mammalian vestibular system can be modulated. Administration of a compound can be carried out using one of a variety of methods known to those of skill in the art. For example, a compound can be administered intravenously, intramuscularly, by ingestion, inhalation, absorption such as absorption through the skin or tear duct, or any other method of administration known in the art. A compound can be administered, for example, to a fruit fly by ingestion. An appropriate method of administering a compound to an invertebrate can be determined by those skilled in the art and will depend, for example, on the type and developmental stage of the invertebrate, whether the invertebrate is active or inactive at the time of administering, whether the invertebrate is exhibiting a geotactic behavior at the time of administering, the number of animals being assayed, and the chemical and biological properties of the compound (e.g. solubility, digestibility, bioavailability, stability and toxicity) . For example, as shown in Example I below, antihistamine can be administered to Drosophila melanogaster by dissolving the drugs in fly food and providing the food to the flies. A compound that can modulate a mammalian vestibular system, invertebrate geotaxis, or protein expression or activity can be administered to a subject in an effective amount. The term "effective amount" of a compound, as used herein, refers to an amount that causes a change in a mammalian vestibular system, invertebrate geotaxis, or protein expression or activity. Measurement of such a. change can be made by one of a variety of assay methods known to one of skill in the art and include monitoring invertebrate geotactic behavior, measurement of gene expression level, or measurement of activity levels of one or more proteins; measurements can also include clinical indices such as assessment of improvement of a graviperceptive disorder such as vertigo or motion sickness in a subject by decreased symptoms related to the graviperceptive disorder, for example, nausea, dizziness, fatigue and the like. A candidate compound can be administered to an invertebrate in a single dose, or in multiple doses. The modulation of invertebrate geotactic behavior will be dose dependent. An effective amount of a compound used in the methods of the invention can be determined by those skilled in the art, and can depend on the chemical and biological properties of the compound and the method of contacting. Exemplary concentration ranges to test include from about 10 μg/ml to about 500 mg/ml, such as from about 100 μg/ml to 250 mg/ml, including from about 1 mg/ml to 200 mg/ml. A candidate compound can also be administered to a mammal. Administration to a mammal can be in a single dose, or in multiple doses. The modulation of a mammalian vestibular system will be dose dependent. An effective amount of a compound used in the methods of the invention can be determined by those skilled in the art, and can depend on the chemical and biological properties of the compound and the method of contacting. Exemplary concentration ranges to test include from about 10 μg/ml to about 500 mg/ml, such as from about 100 μg/ml to 250 mg/ml, including from about 1 mg/ml to 200 mg/ml. Exemplary mammals to which a candidate compound can be administered include mice, rats, rabbits, pigs, dogs, cats, non-human primates, an other animals known to be useful for laboratory testing. A subject with a graviperceptive disorder such as motion sickness, vertigo, labyrinthitis, Meniere's disease, acoustic neuroma, multiple sclerosis, syphilis, trauma, infection of the middle ear, exposure to ototoxic agents or epilepsy sickness can be treated for such a disorder by administering to the subject an effective amount of a compound that modulates a mammalian vestibular system. In treatment of the disorder, administration of an effective amount of the compound can be carried out upon a single occasion or multiple occasions. Administration can be regular, periodic administration such as one administration per day, symptomatic administration such as upon experiencing increasing nausea or dizziness, or prophylactic administration, such as prior to road, sea, air or space travel . It will be understood that the efficacy and safety of a compound in laboratory mammals can be evaluated before administering the compound to humans or veterinary animals. For example, the compound can be tested for its maximal efficacy and any potential side-effects using several different invertebrates or laboratory mammals, across a range of doses, in a range of formulations, and at various times of day, such as before or after sleeping, before or after eating, and the like. Generally, a compound identified using the methods of the invention will cause few or no deleterious or unwanted side effects. The term "conditions" when used in the context of invertebrate geotactic behavior refers to environmental and biological factors that can increase, decrease or otherwise modify invertebrate geotactic behavior. Environmental factors encompass the physical environment such as temperature, pressure, light intensity, light position, and the like; components of the gaseous environment such as humidity, % oxygen, presence of a compound such as a drug or hormone, and the like; and the structural makeup of the chamber in which the invertebrate is housed, including volume, particularly as it influences density of invertebrates, shape, composition of the chamber, and the like. Typical environmental conditions are about 20°C, 1 atmosphere, in the presence of a horizontal 15 W fluorescent light source, at ambient air conditions. An exemplary chamber is provided in the Examples below. Biological factors that can influence invertebrate geotaxis can include genetic factors including presence of particular alleles of genes or chromosomes, either naturally occurring or induced in the laboratory, biorhythmic factors such as time of day, relative activity level of an invertebrate, length of time an invertebrate has been active, and the like, also include biochemical factors such as developmental and hormonal state of an invertebrate, fasting state of the invertebrate, presence in the invertebrate of a compound administered by, for example, ingestion, and the like, and further include factors such as gender and age of the invertebrate. Typically, geotactic behavior experiments are carried out on adult invertebrates during the daytime, at least about two hours after sunrise and at least about two hours before sunset, and at least two hours after invertebrates have been at a relatively increased level of activity. An "increased level of activity" as used herein refers to the "alert" state of an invertebrate that often occurs in the daytime in contrast to the "resting" state of an invertebrate that often occurs during the nighttime. Change of some of these conditions can result in a change in geotactic behavior of an invertebrate. For example, addition of a compound such as a drug to the gaseous environment can result in modulated invertebrate geotaxis . Conditions in which a first invertebrate strain can exhibit a geotactic behavior different than a geotactic behavior in a second invertebrate strain refers to environmental or biorhythmic factors that, when imposed on two different invertebrate strains, results in the two strains exhibiting dissimilar geotactic behavior. For example, conditions can cause a first invertebrate strain to exhibit negative geotaxis while cause a second strain to exhibit positive geotaxis. The first and second strain can be any combination of strains, including a mutant strain and a wild type strain, two different mutant strains, and also can be two different or even identical strains, where the two strains differ in, for example, age, gender, presence of a drug in one strain or different drugs in the two strains, and the like. These conditions also include the structure of the chamber in which the invertebrates are housed. For example, two strains can be placed in a chamber that is so shaped as to have pathways that lead upwards, against the force of gravity, as well as pathways that lead downwards, with the force of gravity. In such a chamber, a first strain can demonstrate strongly negative geotaxictic behavior, thereby rising along the upward pathways, while a second strand can demonstrate normal or "wild-type" geotaxictic behavior, in which no particular preference is manifest for either rising or descending along the various pathways. In a chamber of such a shape, further environmental or biorhythmic factors can be changed, for example, by administering a compound to the invertebrates, which can change the geotactic behavior of one or both invertebrate strains. Determination of a geotactic behavior of a first invertebrate that is termed "different" than a geotactic behavior of a second invertebrate can be accomplished by analysis of a geotactic behavior of the two invertebrates. For example, in order for a geotactic behavior of a first invertebrate to be different than a geotactic behavior of a second invertebrate, the mean geotatic measurement, typically termed the geotaxis score, of the first invertebrate will differ from the geotaxis score of the second invertebrate strain if a pairwise t-test of two scores is significantly different at the 0.05 level, or if multiple pairwise comparisons between strains are significantly different after applying a correction for experiment wise-error. A significantly different score refers to a score that is different by a statistically meaningful amount. Alternatively, two geotactic scores are considered different if a first mean geotactic score is not within as desired region of the probability distribution of the second geotactic score. For example, a first mean geotactic score can be different if it is not within the 80% probable region of a probability distribution of the second geotactic score, or within the 85%, 90%, 95% or 98% probable region of the distribution of the second geotactic score. Correspondingly, geotactic scores considered to be substantially the same are geotactic scores that do not differ by a more than a desired standard deviation or are within a desired probable region of a probability distribution. Methods for the determination of mean, standard deviation and characteristics of normal distributions are known in the art as demonstrated by texts such as Biostatistical Analysis, 4th ed. , Zar, Prentice-Hall Inc. (1999) . Measuring gene expression levels can be carried out by determining the amount of RNA transcribed or protein translated from each of one or more genes. This amount can be relative to another amount, for example, the RNA transcribed from a constitutively expressed gene, relative to total RNA or protein, or can be an absolute measure of the amount of RNA transcribed or protein translated. A variety of assays well known in the art can be used to evaluate expression of particular genes, including the invertebrate genes comprising SEQ ID NOS: 1-261, and mammalian genes substantially the same as invertebrate genes comprising SEQ ID NOS: 1-261. Assays that detect mRNA expression generally involve hybridization of a detectable agent, such as a complementary primer or probe, to the nucleic acid molecule. Such assays include, for example, RNA or dot blot analysis, primer extension, RNase protection assays, reverse-transcription PCR, competitive PCR, real-time quantitative PCR (TaqMan PCR) , nucleic acid array analysis, and the like. Additionally, constructs containing the promoter of a gene and a reporter gene (e.g. β-galactosidase, green fluorescent protein, luciferase) can be made by known methods, and used to generate transgenic non-human mammals and invertebrates. In transgenic non-human mammals, expression of the reporter gene is a marker for expression of a gene that modulates a mammalian vestibular system. Likewise, expression of a reporter gene in transgenic invertebrates is a marker for expression of a gene that modulate a geotactic behavior. Assays that detect protein expression can also be used to evaluate expression of particular genes. Such assays generally involve binding of a detectable agent, such as an antibody or selective binding agent, to the polypeptide in a sample of cells or tissue from the animal. Protein assays include, for example, immunohistochemistry, immunofluorescence, ELISA assays, immunoprecipitation, immunoblot or other protein-blot analysis, and the like. Those skilled in the art will appreciate that the methods of the invention can be practiced in the absence of knowledge of the sequence or function of the genes associated with a geotactic behavior or genes that modulate the mammalian vestibular system whose expression is evaluated. Expression of such genes can thus be evaluated using assays that examine overall patterns of gene expression characteristic of a geotactic behavior. It will be understood that as these genes are identified or sequenced, specific probes, primers, antibodies and other binding agents can be used to evaluate their expression more specifically using any of the above detection methods. One assay to examine patterns of expression of genes associated with a geotactic behavior or genes that modulate the mammalian vestibular system, that does not require prior knowledge of their sequence, is mRNA differential display, which is described, for example, in Cirelli et al., Mol. Brain Res. 56:293 (1998) and Liang and Pardee, Mol. Biotech. 10:261-7 (1998). In such a method, RNA from the animal is reverse-transcribed and amplified by PCR using a particular combination of arbitrary primers. A detectable label, such as an enzyme, biotin, fluorescent dye or a radiolabel, is incorporated into the amplification products. The labeled products are then separated by size, such as on acrylamide gels, and detected by any method appropriate for detecting the label, including autoradiography, phosphoimaging or the like. Such a method allows concurrent examination of expression of thousands of RNA species. Methods for determining which RNA species correspond to a gene associated with a geotactic behavior or a gene that modulates the mammalian vestibular system, are disclosed herein, for example, comparing gene expression levels in invertebrates that exhibit different geotactic behavior. It can be readily determined whether a particular compound alters this pattern of gene expression, such as by increasing or decreasing the intensity of bands corresponding to genes associated with a geotactic behavior or genes that modulate the mammalian vestibular system. A further assay to examine patterns of expression of genes is array analysis, in which nucleic acids representative of all or a portion of the genome of an invertebrate or mammal, or representative of all or a portion of expressed genes of an invertebrate or mammal, are attached to a solid support, such as a filter, glass slide, chip or culture plate. Detectably labeled probes, such as cDNA probes, are then prepared from mRNA of an animal, and hybridized to the array to generate a characteristic, reproducible pattern of spots associated with, for example, a geotactic behavior. It can be readily determined whether a particular candidate compound alters this pattern of gene expression, such as by increasing or decreasing the intensity of one or more spots . Following identification of patterns of gene expression, those skilled in the art can clone the genes, if desired, using standard molecular biology approaches. For example, a band identified by differential display can be eluted from a gel and sequenced, or used to probe a library to identify the corresponding cDNA or genomic DNA. Likewise, a gene from an array can be identified based on its known position on the array, or cloned by PCR or by probing a library. If desired, any of the expression and activity assays described above can be used in combination, either sequentially or simultaneously. Such assays can also be partially or completely automated, using methods known in the art. Samples of the invertebrate collected for measuring gene expression levels can include any organ known or suspected of influencing geotaxis. Exemplary organs can be found in the head, neck, legs and antennae, and include, for example, a brain. Samples can be collected from an invertebrate at various occasions, including before and/or after feeding, before and/or after administration of a compound, before, during and/or after a period of high activity level, or before and/or after participating in a measurement of the geotactic behavior of the invertebrate. Typically, samples are collected under the same conditions as the conditions that geotactic measurements are carried out, for example at about the same time of day, about the same amount of time after feeding, about the same environmental conditions, and the like. Samples can also be collected immediately following measurement of geotactic behavior. For example, samples from a first and a second invertebrate can be collected immediately after subjecting the first and second invertebrates to conditions in which the first invertebrate exhibits a geotactic behavior different than a geotactic behavior exhibited by the second invertebrate. In the context of sample collection, "immediately after" refers to a short time period following measurement of geotactic behavior in which little or no manipulation of the invertebrate occurs after geotactic measurement but prior to sample collection. Typically, this time period is less than 5 minutes after measuring geotactic behavior, but the time period can also be less than 10 minutes, less than 20 minutes or less than 30 minutes after measuring geotactic behavior. Assays to evaluate expression of genes can involve sacrificing the animal at a selected time, homogenizing the entire animal, or a portion containing the brain or sensory organs, and extracting either mRNA or proteins therefrom. Alternatively, such assays can be performed in biopsied tissue from the invertebrate. Gene expression levels can be measured on two or more occasions or in two or more groups of invertebrates, and compared to each other. For example, gene expression can be measured in a strain that exhibits negative geotaxis and gene expression can be measured in a strain showing "normal" (wild type) geotaxis. Gene expression levels of the two strains can then be compared, and genes expressed at significantly different levels identified. Genes that are expressed at significantly different levels can be termed "differentially expressed" genes. Significantly different levels are levels that vary from each other by an amount greater than a reference amount. A reference amount can be, for example, based on the variability of expression levels between invertebrates that ideally would have identical expression levels (i.e., having identical genetic makeup, age, gender, raised under identical conditions, and the like) . In such a situation, a significantly different level can be a difference that is greater than the mean difference observed between expression levels, or greater than the largest expression level difference observed between most or all genes in the ideally identical organisms. Alternatively, significantly different levels can be based on the composite variability of gene expression levels between two or more strains. For example, the mean or median difference between gene expression levels can be determined between a large number of different strains. Any difference in expression that is greater than the mean or median difference can be considered differentially expressed. Other reference levels defining a significant difference can be determined by one of skill in the art according to the desired comparison between two or more invertebrates. Differential expression can also be determined for invertebrates of the same strain that have been subjected to conditions in which a first group of members of a strain exhibit a geotactic behavior different from the geotactic behavior of a second group of members of the strain. This can be carried out, for example, by administration of a compound, presence of light, time of day, and the like. Differential expression is then determined by measuring expression levels in the two groups and identifying genes expressed at significantly different levels. A gene that is differentially expressed in two invertebrate groups that exhibit different levels of geotactic behavior can be considered a gene associated with invertebrate geotactic behavior. As used in regard to invertebrate geotactic behavior, "associated" refers to the correlation of a gene with a modulation in invertebrate geotactic behavior. For example, a gene associated with geotactic behavior can be a gene identified as more highly expressed in invertebrates that exhibit negative geotactic behavior than in invertebrates that exhibit positive geotactic behavior, or alternatively, wild type geotactic behavior. The sequence and function of such an associated gene can be previously known or unknown. Exemplary genes associated with invertebrate geotactic behavior are protein tyrosine phosphatase, non-muscle myosin heavy-chain, cysteine proteinase-1, serine/threonine protein kinase, macrophage receptor protein, cryptochrome, prospero, pigment- dispersing-factor, cyclin A and pendulin. Additional exemplary genes associated with invertebrate geotactic behavior are genes that contain a nucleic acid sequence selected from SEQ ID NOS: 1-261. Such a gene associated with invertebrate geotactic behavior can be substantially the same as at least one mammalian gene that modulates a mammalian vestibular system. Therefore, genes such as protein tyrosine phosphatase, non-muscle myosin heavy- chain, cysteine proteinase-1, serine/threonine protein kinase, macrophage receptor protein, cryptochrome, prospero, Pigment-dispersing factor, cyclin A and pendulin, and genes that contain a nucleic acid sequence selected from SEQ ID NOS: 1-261 can be substantially the same as genes that modulate a mammalian vestibular system. As used herein, the term "expression profile" refers to any read-out that provides a qualitative or quantitative indication of the expression or activity of a single gene, or of multiple genes. An expression profile can, for example, indicate the expression or activity of one, or of least 2, 5, 10, 20, 50, 100, 265, or more genes. An expression profile can, for example, indicate the expression or activity in a mammal of mammalian homologs of one or more genes associated with invertebrate geotactic behavior. An expression profile can also, for example, indicate the expression or activity in an invertebrate of one more genes associated w th invertebrate geotactic behavior. An expression profile can indicate expression or activity of one, a few, many, or all of these genes. An expression profile can also indicate expression or activity of other genes not previously associated with geotactic behavior. The methods of the invention can be used to identify expression levels of any subset of genes desired to characterize a particular graviperceptive disorder. A subset of genes can be chosen based on functional linkage of the genes including, for example, genes expressing proteins that interact in a signal transduction system or a metabolic system; physical linkage of the genes including, for example, proximity on a chromosome or any other criteria. An expression profile can be, for example, a quantitative or qualitative measure of expression of mRNA expressed by one or more genes. A variety of methods of detecting or quantitating mRNA expression have been described above in connection with invertebrate screening assays and include, but are not limited to, Northern or dot blot analysis, primer extension, RNase protection assays, differential display, reverse-transcription PCR, competitive PCR, real-time quantitative PCR (TaqMan PCR) , and nucleic acid array analysis. An expression profile can also be a quantitative or qualitative measure of expression of polypeptides encoded by one or more genes. Methods of detecting or quantitating protein expression have been described above in connection with invertebrate screening assays, and include, but are not limited to, immunohistochemistry, immunofluorescence, immunoprecipitation, immunoblot analysis, and various types of ELISA analysis, including ELISA analysis using arrays of polypeptide-specific antibodies bound to solid supports. Additional methods include two-dimensional gel electrophoresis, MALDI-TOF mass spectrometry, and ProteinChip™/SELDI mass spectrometry technology. An expression profile can also be a direct or indirect measure of the biological activity of polypeptides encoded by one or more genes. A direct measure of the biological activity of a polypeptide can be, for example, a measure of its enzymatic activity, using an assay indicative of such enzymatic activity. An indirect measure of the biological activity of a polypeptide can be its state of modification (e.g. phosphorylation, glycosylation, or proteolytic modification) or localization (e.g. nuclear or cytoplasmic) , where the particular modification or localization is indicative of biological activity. A further indirect measure of the biological activity of a polypeptide can be the abundance of a substrate or metabolite of the polypeptide, such as a neurotransmitter, where the abundance of the substrate or metabolite is indicative of the biological activity of the polypeptide. Appropriate assays for measuring enzyme activity, polypeptide modifications, and substrates and metabolites or polypeptides, will depend on the biological activity of the particular polypeptide. The appropriate method to use in determining an expression profile can be determined by those skilled in the art, and will depend, for example, on the number of genes being profiled; whether the method is performed in vivo or in a sample; the type of sample obtained; whether the assay is performed manually or is automated; the biological activity of the encoded polypeptide; the abundance of the transcript, protein, substrate or metabolite being detected; and the desired sensitivity, reproducibility and speed of the method. An expression profile can be established in vivo, such as by diagnostic imaging procedures using indicative of the biological activity of the polypeptide. Appropriate assays for measuring enzyme activity, polypeptide modifications, and substrates and metabolites or polypeptides, will depend on the biological activity of the particular polypeptide. The appropriate method to use in determining an expression profile can be determined by those skilled in the art, and will depend, for example, on the number of genes being profiled; whether the method is performed in vivo or in a sample; the type of sample obtained; whether the assay is performed manually or is automated; the biological activity of the encoded polypeptide; the abundance of the transcript, protein, substrate or metabolite being detected; and the desired sensitivity, reproducibility and speed of the method. An expression profile can be established in vivo, such as by diagnostic imaging procedures using detectably labeled antibodies or other binding molecules, or from a sample obtained from an individual. As changes in gene expression in the brain are likely to be most relevant to modulation of geotactic behavior or of a mammalian vestibular system, appropriate samples can contain neural tissue, cells derived from neural tissues, or extracellular medium surrounding neural tissues, in which polypeptides to be detected or their metabolites are present. Thus, an appropriate sample for establishing a expression profile in humans can be, for example, cerebrospinal fluid, whereas in laboratory animals an appropriate sample can be, for example, a biopsy of the brain. follicles, cervix or cheek. Additionally, cells can readily be obtained using slightly more invasive procedures, such as punch biopsies of the breast or muscle, from the bone marrow or, during surgery, from essentially any organ or tissue of the body. An expression profile can also be determined from cells in culture. These cells can be immortalized cells from a selected individual invertebrate or mammal, or can be cells from any known established invertebrate or mammalian cell line, such as those available from ATCC (Mannassas, VA) . The expression profile of these cells can be measured, for example, in the absence and presence of a compound. A compound that modulates the expression of an invertebrate gene associated with geotactic behavior or of a mammalian gene substantially the same as an invertebrate gene associated with geotactic behavior can be a compound that modulates the mammalian vestibular system. The number of different compounds to screen in the methods of the invention can be determined by those skilled in the art depending on the application of the method. For example, a smaller number of candidate compounds would generally be used if the type of compound that is likely to modulate geotactic behavior is known or can be predicted, such as when derivatives of a lead compound are being tested. However, when the type of compound that is likely to modulate geotactic behavior is unknown, it is generally understood that the larger the number of candidate compounds screened, the greater the likelihood of identifying a compound that modulates geotactic behavior. Therefore, the methods of the invention can employ screening individual compounds separately or populations of compounds including small populations and large or diverse populations, to identify a compound that modulates geotactic behavior, and thereby also modulates a mammalian vestibular system. Methods for producing libraries of candidate compounds to use in the methods of the invention, including chemical or biological molecules such as simple or complex organic molecules, metal-containing compounds, carbohydrates, peptides, proteins, peptidomimetics, glycoproteins, lipoproteins, nucleic acids, antibodies, and the like, are well known in the art. Libraries containing large numbers of natural and synthetic compounds also can be obtained from a variety of commercial sources. Genetic methods of identifying new genes associated with invertebrate geotactic behavior that are applicable to a variety of invertebrates are known in the art. For example, the invertebrate can be mutagenized using chemicals, radiation or insertions (e.g. transposons, such as P element mutagenesis) , appropriate crosses performed, and the progeny screened for phenotypic differences in geotatic behavior compared with normal controls. The gene can then be identified by a variety of methods including, for example, linkage analysis or rescue of the gene targeted by the inserted element. Genetic methods of identifying genes are described for Drosophila, for example, in Greenspan, Fly Pushing: The Theory and Practice of Drosophila Genetics, Cold Spring Harbor Laboratory Press (1997). In accordance with another embodiment of the invention, a method is provided for identifying a gene that modulates a mammalian vestibular system. The invention is carried out by obtaining a first and a second strain of an invertebrate, subjecting the first and second invertebrate strains to conditions in which said first strain exhibits a geotactic behavior different than a geotactic behavior exhibited by the second strain, measuring gene expression levels in the first and second strains, and identifying one or more genes that are differentially expressed in the first strain relative to the second strain, where a mammalian gene containing substantially the same nucleic acid sequence as the one or more differentially expressed genes modulates the mammalian vestibular system. There are numerous important diagnostic, therapeutic, and screening applications that arise from identification of novel genes that modulate a mammalian vestibular system, together with knowledge that modulation of expression or activity of such genes that modulate a mammalian vestibular system is an effective method of modulating a mammalian vestibular system. For example, an expression or activity profile of one or many genes that modulate a mammalian vestibular system can be established .that is a molecular fingerprint of the sensitivity of a mammalian vestibular system or disorder thereof. Thus, in diagnostic applications, it can readily be determined, by comparing the expression profile of an individual to one or more reference profiles, whether that individual suffers from, or is susceptible to, a particular graviperceptive disorder. Likewise, the sensitivity of a mammalian vestibular system and the effect of medications or medical procedures on the sensitivity of a mammalian vestibular system, can be determined at the molecular level. Such determinations allow for more appropriate determination and use of therapeutics for treating graviperceptive disorders . In screening applications, identification of genes that modulate a mammalian vestibular system and their role in the sensitivity of a mammalian vestibular system allows novel compounds that modulate a mammalian vestibular system to be identified, lead compounds to be validated, and the molecular effects of these compounds and other known compounds that modulate a mammalian vestibular system to be characterized, by determining the effect of these compounds on an expression profile. For example, the ability of a compound to alter an expression profile of an individual to correspond more closely to a desired sensitivity of a mammalian vestibular system can be determined. Likewise, the ability of a compound, administered to an individual with a particular graviperceptive disorder, to alter the expression profile to correspond more closely to the profile of an unaffected or normal individual can be determined. The compounds so identified, validated or characterized from such assays can be administered to unaffected or normal individuals to enhance or reduce sensitivity of a mammalian vestibular system, as desired, or to individuals having a graviperceptive disorder to treat the disorder or induce more normal mammalian vestibular system sensitivity. The invention thus provides an isolated nucleic acid having mammalian vestibular system-modulating activity, or fragment thereof, comprising substantially the same nucleic acid sequence as a nucleic acid selected from the group consisting of SEQ ID NOS: 1-261. The isolated nucleic acid molecules of the invention having mammalian vestibular system modulating activity contain sequences substantially the same as sequences from genes associated with invertebrate geotactic behavior identified from mRNA differential display analysis performed in Drosophila melanogaster (SEQ ID NOS:l-258). SEQ ID NOS: 1-23 correspond to genes that are downregulated in invertebrates that exhibit negative geotactic behavior relative to invertebrates that exhibit positive geotactic behavior. SEQ ID NOS: 24-258 correspond to genes that are upregulated in invertebrates that exhibit negative geotactic behavior relative to invertebrates that exhibit positive geotactic behavior. In accordance with the present invention, various nucleic acids selected from SEQ ID NOS: 1-261 are homologous to known genes. For example, SEQ ID NO: 233 is similar to mouse α-tectorin, which is one of the major noncollagenous components of the tectorial membrane of the inner ear (Legan et al., J. Biol. Chem. 272:8791-8801 (1997)). Mutations in human α-tectorin cause a variety of hereditary forms of deafness and inner ear disorders (Verhoeven et al., Nature Genet. 19:60-62 (1998); Mustapha et al., Hum. Molec. Genet. 8:409-412 (1999)). The nucleic acid of SEQ ID NO: 108 is similar to the protein gp330/megalin/SGP2, which encodes an endocytic receptor for apolipoprotein J/clusterin (Kirszbaum et al . , EMBO J. 8:711-718 (1989)) and is widely expressed in the brain (Danik et al., J. Com . Neurol. 334:209-227 (1993)). Knockout mice die perinatally with altered development of the brain (Wilnow et al., Proc. Natl. Acad. Sci. USA 93:8460-8464 (1996)). SEQ ID NOS: 117 and 250 are similar to two human genes involved in regulating synaptic function which are respectively termed PIN, protein inhibitor of neuronal nitric oxide synthase (Jaffrey and Snyder, Science 274:774-777 (1996)), and SV2, synaptic vesicle transporter-2 (Schivell et al., J. Biol. Chem. 271:7770- 7775 (1996)). SEQ ID NO: 225 is similar to a human gene, APP- binding protein, which can be associated with synaptic mechanisms (Russo et al., FEBS Lett. 434:1-7 (1998)). The SCA2/ataxin-2 gene, which is similar to SEQ ID NO:l, is responsible for a hereditary spinocerebellar ataxia in humans and mice (Imbert et al., Nature Genet. 14:285-291 (1997)). It is expressed throughout brain especially in the trochlear nuclei which receive projections from the ear (Pulst et al., Nature Genet. 14:269-276 (1996)). The protein contains a consensus cleavage site for an obligatory processing step by apopain, a cysteine protease (Sanpei et al., Nature Genet. 14:277-284 (1996)). Thus this gene not only plays a role in a hereditary ataxia, but also requires cleavage by a cysteine-protease . SEQ ID NO: 113 corresponds to Cpl , the fly's cysteine protease (Blake et al., Dev. Biol. 203:177-188 (1998)). In this context, it may be significant that SEQ ID NO:l and 113 are reciprocally regulated in the two different geotactic strains. SEQ ID NO: 98 corresponds to protein tyrosine phosphorylase Ptp6lF. Protein tyrosine phosphatases regulate the cytoskeleton (Helmke et al, J. Cell. Sci. Ill :2465-2475 (1998); Guvakova and Surmacz, Exp. Cell. Res. 251:244-255 (1999); Boonstra, FASEB J. 13:S35-S42 (1999)), which is key in the mechanotransduction events associated with gravity perception (Ingber, FASEB J. 13:S3-S15 (1999)). Non-muscle myosin heavy chain zip, corresponding to SEQ ID NO: 37, is another regulator of the cytoskeleton (Young et al., Genes Dev. 7:29-41 (1993) ) . Non-muscle myosins have also been identified in hereditary ataxias and inner ear disorders such as Usher Syndrome in humans (Weil et al., Proc Natl. Acad. Sci. USA 93:3232-3237 (1995)) and Snell's walzer in mice (Avraham et al., Hum. Molec. Genet. 6:1225-1231 (1997)). SEQ ID NO: 191 is similar to α-tubulin, which also fits into this cytoskeletal group, as does the actin-binding double- zinc-finger protein, similar to SEQ ID NO: 21 (Roof et al., J. Cell. Biol. 138:575-588 (1997)). Also relevant as a source of phenotypic differences between the selected strains is axon guidance, which is influenced by proteins such as protein tyrosine phosphatases (Desai et al., Cell 84:599-609 (1996)), actin-binding double zinc-finger proteins (Lundquist et al., Neuron 21:385-392 (1998)) and serine/threonine kinases, such as the serine/threonine kinase nemo, similar to SEQ ID NO: 256 (Broughton et al., J. Cell. Biochem. 60:584-600 (1996); Broughton et al., J ^ Cell. Biochem. 62:484-494 (1996)). SEQ ID NO:174 corresponds to the mfas (midline fasciclin) gene, which is also involved in axon guidance (Hu et al., J. Neurobiol. 35:77-93 (1998)). The croquemort gene in Drosophila , corresponding to SEQ ID NO: 8, encodes a macrophage receptor for apoptotic cells (Franc et al., Immunity 4:431-443 (1996)) and is involved both in apoptosis and in tissue modeling. Of possible relevance to graviperception and response is the onset of apoptosis in vestibular nuclei after prolonged stimulation (Mitchell et al., Neurosci. Lett. 198:153-156 (1995)) and in lymphocytes after space-flight (Lewis et al., FASEB J. 12:1007-1018 (1998)). SEQ ID NO: 166 is similar to DnaJ, a highly conserved protein that mediates gravity responsiveness in plants (Sedbrook et al., Proc. Natl. Acad. Sci. USA 96:1140-1145 (1999)). DNAJ is also associated with spinocerebellar ataxia in humans (Cummings et al., Nat . Genet. 19:148-54 (1998)). Cryptochrome (cry) , which corresponds to SEQ ID NO: 17, is a flavo-protein highly conserved from flies to plants to humans that is involved in responses to environmental stimuli (Cashmore et al., Science 284:760-765 (1999)). Several sequences corresponding to Drosophila genes with roles in neuronal development or signaling also showed differential expression. These include SEQ ID NO: 15, corresponding to the prospero gene, a homeobox gene important for sensory neuron specification (Vaessin et al., Cell 67:941-953 (1991), Reddy and Rodrigues, Development 126:2083-2092 (1999)) SEQ ID NO:3, and homologous to PROX1 (human homolog NP_002754) corresponding to pigmen t dispersing factor which is involved in mediating circadian rhythms and interacting with circadian clock components, such as cryptochrome (Park and Hall, J. Biol. Rhythms 13:219-228 (1998), Ceriani et al., Science 285:553-556 (1999)); SEQ ID NO: 128, corresponding to the cell cycle gene cyclin A; and SEQ ID NO: 258, corresponding to the Pendulin gene homolog of a nuclear import protein (Torok et al., J. Cell Biol. 129:1473-1489 (1995)). The isolated nucleic acid molecules comprising SEQ ID NO: 1-261 hybridize to mammalian genes, and thus can be used in the diagnostic and screening methods described below. Additionally, the isolated nucleic acid molecules containing sequences substantially the same as one of SEQ ID NOS: 1-261 can be administered in gene therapy methods, including antisense and ribozyme methods, to increase or decrease expression of polypeptides that modulate a mammalian vestibular system. The isolated nucleic acid molecules of the invention can also be used as probes or primers to identify larger cDNAs or genomic DNA, or to identify homologs of the nucleic acid molecules in other species. The isolated nucleic acid molecules can further be expressed to produce polypeptides for use in producing antibodies or for rationally designing inhibitory or stimulatory compounds. Other uses for the isolated nucleic acid molecules of the invention can be determined by those skilled in the art. As used herein, the term "nucleic acid molecule" refers to both deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) molecules, and can optionally include one or more non-native nucleotides, having, for example, modifications to the base, the sugar, or the phosphate portion, or having a modified phosphodiester linkage. The term nucleic acid molecule includes both single-stranded and double-stranded nucleic acids, representing the sense strand, the anti-sense strand, or both, and includes linear, circular or branched molecules. Exemplary nucleic acid molecules include genomic DNA, cDNA, mRNA and oligonucleotides, corresponding to either the coding or non-coding portion of the molecule, and optionally containing sequences required for expression. A nucleic acid molecule of the invention, if desired, can additionally contain a detectable moiety, such as a radiolabel, a fluorochrome, a ferromagnetic substance, a luminescent tag or a bindably detectable agent such as biotin. The term "isolated" in reference to a nucleic acid molecule is intended to mean that the molecule is substantially removed or separated from components with which it is naturally associated, or otherwise modified by a human hand, thereby excluding nucleic acid molecules as they exist in nature. An isolated nucleic acid molecule of the invention can be in solution or suspension, or immobilized on a filter, glass slide, chip, culture plate or other solid support. The degree of purification of the nucleic acid molecule, and its physical form, can be determined by those skilled in the art depending on the intended use of the molecule. The term "comprising" or "containing" in reference to a nucleic acid molecule of the invention, is intended to mean that the nucleic acid molecule can contain additional nucleotide sequences at either the 5' or 3' end of the recited sequence, or branching from an internal position within the recited sequence. The additional nucleotide sequences can, if desired, correspond to sequences that naturally occur within the gene, including intron or exon sequences, promoter sequences, coding sequence, or untranslated regions. Alternatively, the additional nucleotide sequence can correspond to linkers or restriction sites useful in cloning applications; to other regulatory elements such as promoters and polyadenylation sequences that can be useful in gene expression; to epitope tags or fusion proteins useful in protein purification; or the like. Those skilled in the art can determine appropriate sequences flanking the recited nucleotide sequences for a particular application of the method. The invention also provides isolated oligonucleotides containing at least 15 contiguous nucleotides of a nucleotide sequence referenced as SEQ ID NOS: 1-261, or the antisense strand thereof. The isolated oligonucleotides of the invention are able to specifically hybridize to nucleic acid molecules associated with invertebrate geotaxis or with modulation of a mammalian vestibular system under moderately or highly stringent hybridization conditions and thus can be advantageously used, for example, as probes to detect DNA or RNA of a gene associated with invertebrate geotaxis or with modulation of a mammalian vestibular system in a sample; as sequencing or PCR primers; as antisense reagents to administer to an individual to block translation of RNA in cells; or in other applications known to those skilled in the art in which hybridization to a nucleic acid molecule associated with invertebrate geotaxis or with modulation of a mammalian vestibular system is desirable. As used herein, the term "oligonucleotide" refers to a nucleic acid molecule that includes at least 15 contiguous nucleotides from the reference nucleotide sequence, can include at least 16, 17, 18, 19, 20 or at least 25 contiguous nucleotides, and often includes at least 30, 40, 50, 60, 70, 80, 90, 100, 125, 150, 175, 200 or more contiguous nucleotides from the reference nucleotide sequence. As used herein, the term "specifically hybridize" refers to the ability of a nucleic acid molecule to hybridize, under moderately or highly stringent conditions as described above, to a desired nucleic acid molecule, without substantial hybridization under the same conditions with nucleic acid molecules that are not the desired nucleic acid molecule. Those skilled in the art can readily determine whether an oligonucleotide of the invention hybridizes to the recited nucleic acid sequence under moderately or highly stringent conditions by performing a hybridization assay in the presence of other nucleic acid molecules, such as total cellular nucleic acid molecules, and detecting the presence or absence of hybridization to the other nucleic acid molecules. Depending on the intended use of the oligonucleotides of the invention, those skilled in the art can determine whether it is necessary to use an oligonucleotide that specifically hybridizes to the recited nucleic acid molecules. For example, when there are a large number of potential contaminating nucleic acid molecules in the sample, it may be desirable to use an oligonucleotide that specifically hybridizes to the recited nucleic acid molecules. However, when background hybridization is not considered detrimental, when there are few contaminating molecules, or when the oligonucleotide is being used in conjunction with a second molecule, such as a second primer, an oligonucleotide of the invention can be used that does not specifically hybridize to the recited nucleic acid molecules . If desired, the oligonucleotide containing at least 15 contiguous nucleotides of a nucleotide sequence referenced as SEQ ID NOS: 1-261 can further be capable of specifically hybridizing with a reference nucleic acid molecule. Such a reference nucleic acid sequence can be any pre-determined sequence such as a ployA sequence, a sequence containing a restriction site sequence or a sequence that uniquely identifies the invention oligonucleotice (e.g. a "zip code" sequence). In one embodiment, the invention provides a primer pair for detecting nucleic acid molecules associated with invertebrate geotaxis or with modulation of a mammalian vestibular system. The primer pair contains two isolated oligonucleotides, each containing at least 15 contiguous nucleotides of one of the nucleotide sequences referenced as SEQ ID NOS: 1-261, with one sequence representing the sense strand, and one sequence representing the anti-sense strand. The primer pair can be used, for example, to amplify nucleic acid molecules associated with invertebrate geotaxis or with modulation of a mammalian vestibular system by RT-PCR or PCR. The isolated nucleic acid molecules and oligonucleotides of the invention can be produced or isolated by methods known in the art. The method chosen will depend, for example, on the type of nucleic acid molecule one intends to isolate. Those skilled in the art, based on knowledge of the nucleotide sequences disclosed herein, can readily isolate the nucleic acid molecules of the invention as genomic DNA, or desired introns, exons or regulatory sequences therefrom; as full-length cDNA or desired fragments therefrom; or as full-length mRNA or desired fragments therefrom, by methods known in the art. One useful method for producing an isolated nucleic acid molecule of the invention involves amplification of the nucleic acid molecule using the polymerase chain reaction (PCR) and oligonucleotide primers specific for the desired nucleic acid molecule and, optionally, purification of the resulting product by gel electrophoresis. Either PCR or reverse-transcription PCR (RT-PCR) can be used to produce a nucleic acid molecule having any desired nucleotide boundaries. Desired modifications to the nucleic acid sequence can also be introduced by choosing an appropriate primer with one or more additions, deletions or substitutions. Such nucleic acid molecules can be amplified exponentially starting from as little as a single gene or mRNA copy, from any cell, tissue or species of interest. A further method of producing an isolated nucleic acid molecule of the invention is by screening a library, such as a genomic library, cDNA library or expression library, with a detectable agent. Such libraries are commercially available or can be produced from any desired tissue, cell, or species of interest using methods known in the art. For example, a cDNA or genomic library can be screened by hybridization with a detectably labeled nucleic acid molecule having a nucleotide sequence disclosed herein. Additionally, an expression library can be screened with an antibody raised against a polypeptide encoded by a nucleic acid disclosed herein. The library clones containing nucleic acid molecules of the invention can be isolated from other clones by methods known in the art and, if desired, fragments therefrom can be isolated by restriction enzyme digestion and gel electrophoresis. Furthermore, isolated nucleic acid molecules and oligonucleotides of the invention can be produced by synthetic means. For example, a single strand of a nucleic acid molecule can be chemically synthesized in one piece, or in several pieces, by automated synthesis methods known in the art. The complementary strand can likewise be synthesized in one or more pieces, and a double-stranded molecule made by annealing the complementary strands. Direct synthesis is particularly advantageous for producing relatively short molecules, such as oligonucleotide probes and primers, and nucleic acid molecules containing modified nucleotides or linkages . In one embodiment, the isolated nucleic acid molecules or oligonucleotides of the invention are attached to a solid support, such as a chip, filter, glass slide or culture plate, by either covalent or non-covalent methods. Methods of attaching nucleic acid molecules to a solid support, and the uses of nucleic acids in this format in a variety of assays, including manual and automated hybridization assays, are well known in the art. A solid support format is particularly appropriate for automated diagnostic or screening methods, where simultaneous hybridization to a large number of genes associated with invertebrate geotaxis or with modulation of a mammalian vestibular system is desired, or when a large number of samples are being handled. In another embodiment, the invention provides kits containing two or more isolated nucleic acid molecules or oligonucleotides. At least one nucleic acid molecule of the kit contains a nucleotide sequence selected from the group consisting of SEQ ID NOS: 1-261, or modification thereof or at least 15 contiguous nucleotides of a nucleic acid sequence referenced as SEQ ID NO: 1-261. An exemplary kit is a solid support containing an array of isolated nucleic acid molecules or oligonucleotides of the invention, including, for example, at least 3, 5, 10, 20, 30, 40, 50, 75, 100, 265 or more isolated nucleic acid molecules or oligonucleotides . A further exemplary kit contains one or more PCR primer pairs, or two or more hybridization probes, which optionally can be labeled with a detectable moiety for detection of nucleic acid molecules. The kits of the invention can additionally contain instructions for use of the molecules for diagnostic purposes in a clinical setting, or for drug screening purposes in a laboratory setting. If desired, the kits containing two or more isolated nucleic acid molecules or oligonucleotides can contain nucleic acid molecules corresponding to genes that are upregulated in invertebrates exhibiting negative geotactic behavior, or are downregulated in invertebrates exhibiting negative geotactic behavior. Additionally, the kits containing two or more isolated nucleic acid molecules or oligonucleotides can contain nucleic acid molecules corresponding to sequences identified from Drosophila screens or other invertebrate screens, from rat screens, from screens in other mammals, or any combination thereof. The invention also provides a vector containing an isolated nucleic acid molecule associated with invertebrate geotaxis or with modulation of a mammalian vestibular system. The vectors of the invention are useful for subcloning and amplifying an isolated nucleic acid molecule, for recombinantly expressing a polypeptide, and in gene therapy applications, described further below. A vector of the invention can include a variety of elements useful for cloning and/or expression of nucleic acid molecules associated with invertebrate geotaxis or with modulation of a mammalian vestibular system, such as enhancer sequences and promoter sequences from a viral, bacterial, invertebrate or mammalian gene, which provide for constitutive, inducible or cell-specific RNA transcription; transcription termination and RNA processing signals, including polyadenylation signals, which provide for stability of a transcribed mRNA sequence; an origin of replication, which allows for proper episomal replication; selectable marker genes, such as a neomycin or hygromycin resistance gene, useful for selecting stable or transient transfectants in mammalian cells, or an ampicillan resistance gene, useful for selecting transformants in prokaryotic cells; and versatile multiple cloning sites for inserting nucleic acid molecules of interest. A variety of cloning and expression vectors are commercially available, and include, for example, viral vectors such as a bacteriophage, baculovirus, adenovirus, adeno-associated virus, herpes simplex virus and retrovirus; cosmids or plasmids; bacterial artificial chromosome vectors (BACs) and yeast artificial chromosome vectors (YACs) . Such vectors and their uses are well known in the art . The invention also provides host cells that contain a vector containing a nucleic acid molecule of the invention. Exemplary host cells include mammalian primary cells; established mammalian cell lines, such as COS, CHO, HeLa, NIH3T3, HEK 293-T and PC12 cells; amphibian cells, such as Xenopus embryos and oocytes; and other vertebrate cells. Exemplary host cells also include insect cells (e.g. Drosophila ) , yeast cells (e.g. S . cerevisiae, S . pombe, or Pichia pastoris) and prokaryotic cells (e.g. E. coli ) . Further exemplary host cells are cells publicly available through sources such as ATCC (Manassas, VA) . Methods of introducing a vector of the invention into such host cells are well known in the art. The methods of isolating, cloning and expressing nucleic acid molecules of the invention referred to herein are routine in the art and are described in detail, for example, in Sambrook et al., Molecular Cloning: A Laboratory Manual, Cold Spring Harbor Laboratory, New York (1992) and in Ansubel et al . , Current Protocols in Molecular Biology, John Wiley and Sons, Baltimore, MD (2000) , which are incorporated herein by reference. The invention further provides transgenic non-human animals that are capable of expressing wild-type nucleic acids, dominant-negative nucleic acids, antisense nucleic acids, or ribozymes that target nucleic acids, where the nucleic acids are associated with invertebrate geotaxis or with modulation of a mammalian vestibular system. Such animals have correspondingly altered expression of polypeptides associated with invertebrate geotaxis or with modulation of a mammalian vestibular system, and can thus be used to elucidate or confirm the function of such polypeptides, or in whole-animal assays to determine or validate the physiological effect of compounds that potentially modulate a mammalian vestibular system. The transgene may additionally comprise an inducible promoter and/or a tissue specific regulatory element, so that expression can be induced or restricted to specific cell types. Exemplary transgenic non-human animals expressing nucleic acids and nucleic acids that alter gene expression include mouse and Drosophila . Methods of producing transgenic animals are well known in the art. The invention also provides an isolated polypeptide having mammalian vestibular system-modulating activity, or fragment thereof, containing substantially the same amino acid sequence as an amino acid sequence encoded by a nucleic acid sequence selected from the group consisting of SEQ ID NOS: 1-261. Isolated polypeptides of the invention can be used in a variety of applications. For example, isolated polypeptides can be used to generate specific antibodies, or in screening or validation methods where it is desired to identify or characterize compounds that alter the activity of polypeptides that with modulate a mammalian vestibular system. The isolated polypeptides of the invention can be prepared by methods known in the art, including biochemical, recombinant and synthetic methods. For example, invention polypeptides can be purified by routine biochemical methods from neural cells or other cells that express abundant amounts of the polypeptide. An invention polypeptide having any desired boundaries can also be produced by recombinant methods. Recombinant methods involve expressing a nucleic acid molecule encoding the desired polypeptide in a host cell or cell extract, and isolating the recombinant polypeptide, such as by routine biochemical purification methods described above. To facilitate identification and purification of the recombinant polypeptide, it is often desirable to insert or add, in-frame with the coding sequence, nucleic acid sequences that encode epitope tags or other binding sequences, or sequences that direct secretion of the polypeptide. Methods for producing and expressing recombinant polypeptides in vi tro and in prokaryotic and eukaryotic host cells are well known in the art. Furthermore, invention polypeptides can be produced by chemical synthesis. If desired, such as to optimize their functional activity, stability or bioavailability, such molecules can be modified to include D-stereoisomers, non-naturally occurring amino acids, and amino acid analogs and mimetics. Also provided are antibodies that specifically bind polypeptides encoded by the nucleic acid molecules of the invention. Such antibodies can be used, for example, in diagnostic assays such as ELISA assays to detect or quantitate the expression of polypeptides of the invention; to purify polypeptides of the invention; or as therapeutic compounds to selectively target polypeptide of the invention. Such antibodies, if desired, can be bound to a solid support, such as a chip, filter, glass slide or culture plate. As used herein, the term "antibody" is used in its broadest sense to include polyclonal and monoclonal antibodies, as well as antigen binding fragments of such antibodies. An antibody of the invention is characterized by having specific binding activity for a polypeptide associated with invertebrate geotaxis or with modulation of a mammalian vestibular system or fragment thereof of at least about 1 x IO 5 M "1 . Thus, Fab, F(ab') 2 , Fd and Fv fragments of a polypeptide-specific antibody of the invention, which retain specific binding activity for the polypeptide associated with invertebrate geotaxis or with modulation of a mammalian vestibular system, are included within the definition of an antibody. Methods of preparing polyclonal or monoclonal antibodies against polypeptides are well known in the art (see, for example, Harlow and Lane, Antibodies: A Laboratory Manual, Cold Spring Harbor Laboratory Press (1988)). In addition, the term "antibody" as used herein includes naturally occurring antibodies as well as non-naturally occurring antibodies, including, for example, single chain antibodies, chimeric, bifunctional and humanized antibodies, as well as antigen-binding fragments thereof. Such non-naturally occurring antibodies can be produced or obtained by methods known in the art, including constructing the antibodies using solid phase peptide synthesis, recombinant production, or screening combinatorial libraries consisting of variable heavy chains and variable light chains. The invention provides diagnostic methods based on the newly identified and characterized genes described herein. In one embodiment, the invention provides a method of diagnosing a graviperceptive disorder in an individual. The method consists of determining an expression profile of the individual, and comparing that profile to a reference profile indicative of the graviperceptive disorder. Correspondence between the profile of the individual and the reference profile indicates that the individual has the graviperceptive disorder. In one embodiment, at least one of the genes profiled is a gene containing a nucleic acid sequence substantially the same as one of SEQ ID NOS: 1-261. Typically, at least one of the genes profiled is selected from the group consisting of α-tectorin, gp 390, PIN, SV2, PROX1, actin-binding double-zinc-finger protein, SCA2 and APP-binding protein. The methods of diagnosing graviperceptive disorders have numerous applications. For example, a variety of different types of graviperceptive disorders are known, many of which are extremely common in a given population, some of which are more rare. Appropriate diagnosis of a graviperceptive disorder will allow more effective treatments: using currently available mammalian vestibular system modulating compounds or methods; using compounds identified from the screens described herein; using the therapeutic methods described herein; or any combination of these treatments. Likewise, the methods of diagnosing graviperceptive disorders are applicable to monitoring the course of therapy for the disorder, such that appropriate modifications can be made if needed. Furthermore, the methods of diagnosing graviperceptive disorders are applicable to screening for graviperceptive disorders among the general population, or among populations in whom graviperception influences the safety of the individual or the general population (e.g. transportation workers, individual operating heavy machinery, and the like) . Additional useful applications of the diagnostic methods of the invention can be determined by those skilled in the art. Appropriate laboratory animal • models of human graviperceptive disorders of interest are known in the art or can readily be developed by transgenic and knockout methods that alter expression or activity of genes associated with invertebrate geotaxis or with modulation of a mammalian vestibular system, or by pharmacological, surgical or environmental manipulation. The diagnostic methods of the invention can also advantageously be used to characterize previously unrecognized graviperceptive disorders, or to newly categorize graviperceptive disorders, based on characteristic patterns of expression or activity of genes associated with invertebrate geotaxis or modulation of a mammalian vestibular system. Such newly characterized or categorized disorders are also encompassed by the term "graviperceptive disorder." The diagnostic methods of the invention can also be advantageously used to identify the specific genes most closely associated with, and thus likely to play a causative role, in particular graviperceptive disorders. Such genes are targets for modulation by gene therapy methods or by selective targeting of the encoded product with therapeutic compounds. In a further embodiment of the diagnostic methods of the invention, there is also provided a method of determining sensitivity of the vestibular system in an individual. The method consists of determining an expression profile of the individual, and comparing that profile to a reference profile indicative of a predetermined sensitivity of a vestibular system. Correspondence between the profile of the individual and the reference profile indicates that the individual exhibits the predetermined sensitivity of a vestibular system. At least one of the vigilance genes profiled is a gene containing a nucleic acid sequence substantially the same as one of SEQ ID NOS: 1-261. Those skilled in the art understand that the methods described above for diagnosing graviperceptive disorders and determining sensitivity of a vestibular system can readily be applied to methods of screening for novel mammalian vestibular system-modulating compounds; to methods of validating the efficacy of mammalian vestibular system-modulating compounds identified by other methods, such as by the invertebrate screening methods described above; to methods of determining effective dose, time and route of administration of known mammalian vestibular system-modulating compounds; to methods of determining the effects of mammalian vestibular system-modulating compounds on homeostatic regulation of graviperception; to methods of determining the molecular mechanisms of action of known mammalian vestibular system-modulating compounds; and the like. Such methods can be performed in laboratory animals, such as mice, rats, rabbits, dogs, cats, pigs or primates, in veterinary animals, or in humans. Thus, in one embodiment, the invention provides a method of determining the efficacy of a compound in treating a graviperceptive disorder. The method consists of administering a compound to an individual having a graviperceptive disorder, and determining an effect of the compound on the expression profile of the individual. A compound that modulates the expression profile of the individual to correspond to an unaffected or normal profile indicates that the compound is effective in treating the graviperceptive disorder. At least one of the vigilance genes profiled is a gene containing a nucleic acid sequence substantially the same as one of SEQ ID NOS: 1-261. As used herein, the term "treating" is intended to include preventing, ameliorating, curing, and reducing the severity of the graviperceptive disorder or symptoms associated with a graviperceptive disorder. Those skilled in the art understand that any degree of reduction in severity of a graviperceptive disorder can improve the health or quality of life of the individual. The effect of the therapy can be determined by those skilled in the art, by comparison to baseline values for symptoms or clinical or diagnostic markers associated with the disorder. In another embodiment, the invention provides a method of determining the efficacy of a compound in modulating a mammalian vestibular system. The method consists of administering the compound to an individual, and determining an effect of the compound on the expression profile of the individual. A compound that modulates the expression profile indicates that the compound modulates a mammalian vestibular system. At least one of the genes profiled is a gene containing a nucleic acid sequence substantially the same as one of SEQ ID NOS: 1-261. The genes to profile can be determined by those skilled in the art, depending on the type of mammalian vestibular system-modulating compound it is desired to identify or characterize. For example, it may be advantageous to examine the effect of a compound primarily on single genes such as α-tectorin, gp330, PIN, SV2, PROX1, actin-binding double-zinc-finger protein, SCA2 and APP-binding protein; or only primarily on a gene substantially the same as an invertebrate gene whose upregulated expression or activity corresponds to negative invertebrate geotaxis; or only primarily on a gene substantially the same as an invertebrate gene whose downregulated expression or activity corresponds to negative invertebrate geotaxis. The compounds so identified that alter an expression profile can, for example, increase or, decrease graviperception as described above in relation to invertebrate screening methods. The effect of these compounds on graviperception can be corroborated, or further evaluated, in either invertebrates or mammals. Compounds that beneficially modulate the sensitivity of a mammalian vestibular system can be administered as therapeutics to humans and veterinary animals. Once genes associated with graviperceptive disorders are identified, the expression or activity of such genes in humans or veterinary animals can be selectively targeted in order to prevent or treat the graviperceptive disorder. The diagnostic, screening and validation methods of the invention are useful in determining appropriate genes to target and appropriate therapeutic compounds to use for a particular indication. Additional genes associated withinvertebrate geotaxis or with modulation of a mammalian vestibular system can be identified by the methods described herein or by other methods, including differential display, arrays, and other forms of expression or activity analysis in invertebrates and mammals; genetic methods, such as by randomly or specifically targeting genes in model organisms such as Drosophila or mouse, or by mapping genes associated with graviperceptive disorders or from screens for genes associated with other behaviors or molecular pathways that are subsequently determined to be associated with graviperception. Thus, in one embodiment, the invention provides a method of treating a graviperceptive disorder in an individual. The method consists of administering to an individual having a graviperceptive disorder a compound that modulates the expression profile of the individual to correspond to a normal expression profile. At least one of the genes profiled is a gene containing a nucleic acid sequence substantially 'the same as one of SEQ ID NOS: 1-261. In one embodiment, the modulated gene is a gene containing a nucleic acid sequence substantially the same as one of SEQ ID NOS: 1-261. In a further embodiment, the invention provides a method of modulating the vestibular system in a mammal. The method consists of administering to an individual a compound that modulates the activity or expression of a gene that modulates a mammalian vestibular system. In one embodiment, the modulated gene is a gene containing a nucleic acid sequence substantially the same as one of SEQ ID NOS: 1-261. The therapeutic methods of the invention involve determining the effect of the compound on an expression profile. Thus, the therapeutic methods of the invention are not intended to encompass administration of mammaliam vestibular system-modulating drugs which inherently may modulate expression or activity of one or more genes associated with invertebrate geotaxis or with modulation of a mammalian vestibular system, in the absence of a determination that such drugs predictably modulate invertebrate geotaxis or predictably modulate expression profile of one or more genes associated with invertebrate geotaxis or with modulation of a mammalian vestibular system. The effect of the compound on the expression profile of a particular individual to whom the compound is administered need not be determined, however, if the effect of the compound on expression profile in other individuals has previously been established, and such effect on expression profile can be shown to be reproducible across individuals. Of course, it is understood that the expression profile of the individual can, if desired, be determined prior to administration of the compound, and/or monitored during the course of therapy, using modifications of the diagnostic methods described herein. A variety of compounds can be used to modulate the expression profile in individuals having a graviperceptive disorder or in whom modulation of sensitivity of the vestibular system is desired. Compounds can be determined or designed to alter gene expression or activity by a variety of mechanisms, such as by directly or indirectly increasing or decreasing the expression of a gene. For example, a compound can directly interact with a gene promoter; can interact with transcription factors that regulate gene expression; can bind to or cleave a gene transcript (e.g. antisense oligonucleotides or ribozymes); can alter half-life of the transcript; or can itself be an expressible gene associated with invertebrate geotaxis or with modulation of a mammalian vestibular system. A compound can also act by increasing or decreasing activity of one or more encoded polypeptides. For example, the compound can specifically bind to a polypeptide and alter its activity or half-life; can bind to a substrate or modulator of a polypeptide; or can be a polypeptide associated with invertebrate geotaxis or with modulation of a mammalian vestibular system or active portion thereof. The type of compound to be used can be determined by those skilled in the art, and will depend, for example, on factors such as the severity of the disorder; the time period over which treatment of the disorder is desired; the cellular location of the molecule to be targeted; whether the compound is administered in a clinical setting or by the individual; or whether an individual is presently experiencing symptoms of a graviperceptive disorder or anticipates experiencing symptoms of a graviperceptive disorder. Compounds can be formulated in pharmaceutical compositions in such a manner to ensure proper distribution in vivo . For example, the blood-brain barrier (BBB) excludes many highly hydrophilic compounds. To ensure that the compounds of the invention cross the BBB, they can be formulated, for example, in liposomes, or chemically derivatized. Methods of introduction of a compound of the invention include, but are not limited to, intradermal, intramuscular, intraperitoneal, intravenous, subcutaneous, oral, intranasal, intraspinal and intracerebral routes. A compound can also appropriately be introduced by rechargable or biodegradable polymeric devices, which provide for the slow release or controlled delivery of drugs. Appropriate formulations, routes of administration and dose of a compound can be determined by those skilled in the art. If desired, the compounds of the invention can include gene therapy molecules that modulate expression or activity of a gene associated with invertebrate geotaxis or with modulation of a mammalian vestibular system, including genes encoding polypeptides or active or inhibitory portions thereof; genes expressing antisense molecules that block expression of genes associated with invertebrate geotaxis or with modulation of a mammalian vestibular system; and genes expressing ribozymes that target genes associated with invertebrate geotaxis or with modulation of a mammalian vestibular system. Such methods are advantageous in treating graviperceptive disorders or for providing long-lasting prophylactic effects to an individual. Methods of introducing and expressing genes in animals, including humans, are well known in the art. Gene therapy methods can be performed ex vivo, wherein cells (e.g. hematopoietic cells, including stem cells) are removed from the body, engineered to express a polypeptide associated with invertebrate geotaxis or with modulation of a mammalian vestibular system, and returned to the body. Gene therapy methods can also be performed in si tu, in which an expressible nucleic acid molecule is placed directly into an appropriate tissue, such as the brain or CNS, by a direct route such as injection or implantation during surgery. Gene therapy methods can also be performed in vivo, wherein the expressible nucleic acid molecule is administered systemically, such as intravenously. Appropriate vectors for gene therapy can be determined by those skilled in the art for a particular application of the method, and include, but are not limited to, retroviral vectors (e.g. replication-defective MuLV, HTLV, and HIV vectors) ; adenoviral vectors; adeno-associated viral vectors; herpes simplex viral vectors; and non-viral vectors. Appropriate formulations for delivery of nucleic acids can also be determined by those skilled in the art, and include, for example, liposomes; polycationic agents; naked DNA; and DNA associated with or conjugated to targeting molecules (e.g. antibodies, ligands, lectins, fusogenic peptides, or HIV tat peptide) . Gene therapy methods, including considerations for choice of appropriate vectors, promoters, formulations and routes of delivery, are reviewed, for example, in Anderson, Nature 392:25-30 (1998). It is understood that modifications which do not substantially affect the activity of the various embodiments of this invention are also included within the definition of the invention provided herein. Accordingly, the following examples are intended to illustrate but not limit the present invention. EXAMPLE I This example shows the measurement of geotaxis scores for strains of Drosophila that have varying geotactic behaviors. This example also describes preparation of sub-lines of a Drosophila strain that have homozygous sets of chromosomes. Established Drosophila lines that had been subjected to divergent behavioral selection for positive or negative geotaxis, called 'hi' for the negatively geotactic line, ' lo ' for the positively geotactic line, and 'hi5' for the most recently re-selected 'hi' line were obtained from Dr. Jerry Hirsch, Department of Psychology, University of Illinois at Champagne-Urbana and are described in Erlenmeyer-Kimling et al., J. Comp . Phvsiol. Psvchol. 55: 722-731, (1962); Ricker and Hirsch, Behav. Genet. 18: 13-25, (1988), and Stoltenberg and Hirsch, J. Comp. Psvchol. 110:252-259 (1996). These strains and a standard laboratory wild- type strain (Canton-S, obtained from the Bloomington Drosophila Stock Center, Indiana University at Bloomington) were then tested in a geotaxis maze constructed according to the design of Hirsch (J. Comp. Phvsiol. Psvchol. 52:304-308 (1959)) as modified by McMillan and McGuire (Behav. Genet. 22:557-573 (1992)), shown in Figure 1. The geotaxis maze was fashioned from plexiglass and the maze chambers were hollowed out as semi-circular depressions in the slab, such that when the two slabs were bolted together a circular tube was formed in maze. This design thus made it possible to observe the entire time course of the assay. Additionally, this maze is easy to clean and standardize. For each strain, a geotaxis score was determined. In separate measurements, twenty to thirty flies of each strain were loaded into a starting tube on the left (see Figure 1) . The maze was set upright in front of a light source on the right, and, after turning on the light, each strain was scored according to the distribution of the flies in the nine collecting tubes on the right. A perfect score for positive geotaxis would be 1, for negative geotaxis, 9, and for an even distribution, 5. The geotaxis measurments were repeated 3-5 times for each strain (see Table 1). Table 1 A control assay was carried out in which the maze was placed flat on the table so that all nine collecting tubes were chosen by the flies at the same level with respect to gravity. The control assay yielded a random distribution through the maze. Thus, the flies have retained their selected phenotype, even to the extent of showing a lower variance for the recently re-selected 'hi5' strain than for the older 'hi' strain (Stoltenberg and Hirsch, supra, (1996)). In order to decrease the genetic heterogeneity of the Λ hi5' line, sub-lines were derived that were homozygous for a set of chromosomes from the hi5' strain. This was carried out by mating flies of the λ hi5' strain to flies carrying multiple balancer chromosomes according to the method of Greenspan, Fly Pushing: The Theory and Practice of Drosophila Genetics, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY, 1997. Table 2 These results show that the essential phenotype of the selected lines can be captured in homozygous sets of chromosomes and thus can be characterized as a combination of homozygous alleles. The sub-line Λ hi5-la' falls short of the score for the original strain, demonstrating that it contains a subset of the relevant alleles . EXAMPLE II This example demonstrates the dramatic change in geotaxis score that occurs in mutant Drosophila that do not synthesize histamine or wild type Drosophila treated with a histamine receptor antagonist. Several mutants were tested for alterations in geotactic behavior as judged by being consistently more positive or negative than the unselected wild-type strain Canton-S. A mutant with abnormally positive geotactic behavior was the Hdc p211 allele of Histidine decarboxylase, an enzyme in the histamine biosynthetic pathway (Burg et al., EMBO J. 12:911-919 (1993)), as shown in Table 3. Those whose geotactic behavior was similar to Canton-S included for s , a hypomorphic allele of the dg2 locus encoding cGMP-dependent protein kinase (Osborne et al., Science 277:834-836 (1997)), and Appl , a null allele of the gene encoding the Drosophila homolog of the amyloid precursor protein (Luo et al., Neuron 9:595—605 (1992)). Table Extreme negative geotaxis is induced after interference with histamine, in both the histidine decarboxylase mutant Hdc p211 , which fails to make histamine, and in Canton-S flies fed with the histamine receptor antagonist, hydroxyzine. The geotactic behavior of the Hdc p211 mutant and hydroxyzine-treated wild type is particularly significant given the long established role of anti-histamines in the treatment of motion sickness and vertigo (Brand and Perry, Pharmac. Rev. , 18:895-924, 1966) and the ability of histamine to modulate activity in the vestibular system (Yabe et al., Exp. Brain Res . , 93: 249-58, 1993) . These results show that an anti-histamine compound that modulates vestibular system activity can also change fly geotaxis, and that a genetic mutation effecting histamine synthesis can result in geotaxis similar to that caused by the anti-histamine compound. EXAMPLE III This example demonstrates the identification of nucleic acids that are differently expressed in Drosophila that exhibit negative geotaxis in comparison to Drosophila that exhibit positive geotaxis. To examine the molecular basis for the behavioral difference in response to gravity between fly strains, differences in mRNA levels between the 'hi5' and ' lo ' strains were measured. The assays were carried out using microarrays containing 8,800 unique cDNA EST (expressed sequence tag) clones from the Berkeley Drosophila Genome Project and made available through Research Genetics (Huntsville, AL) . This number of cDNA clones represents approximately 65% of the Drosophila genome (Rubin et al., Science 287:2204-2215 (2000)). The microarrays consist of DNA samples printed in a high- density array onto treated glass slides which can then be hybridized with reverse-transcribed, single-stranded cDNA that has incorporated a fluorescently labeled nucleotide, Cy3- or Cy5-conjugated dTTP (Schena et al., Science 270:467-470 (1995); Shalon et al., Genome Res. 6:639-645 (1996) ) . A previous control experiment has determined biological variability by taking animals from different vials and preparing polyA+ RNA independently from each (White et al., Science, 286:2179-2184, 1999). In this previous control experiment, no gene was differentially expressed more than 2.5-fold; so 2.5-3-fold was set as the cut-off criterion for a significant difference in expression in the present experiment. Threshold was arbitrarily set at signal intensity of 1000. The value of 1000 is typically between 2 and 3 standard deviations above the mean background value in microarray experiments . In reciprocal experiments, PolyA+ RNA from -500 isolated heads (mostly brain) from 3-5 day old flies of the 'hi5' strain and the 'lo' strain was fluorescently labeled with Cy3 and Cy5, respectively or Cy5 and Cy3, respectively, according to the method of Schena et al. supra and Shalon et al. supra . In each of the reciprocal experiments, microarrays were simultaneously hybridized with 5 μg fluorescently labeled RNA from both strains. Averaged results from the reciprocal experiments indicated that 25 genes exhibited a 2.5-fold or greater differential in 'lo' relative to 'hi5' (SEQ ID NOS.1-23), and 240 genes exhibited a three-fold or greater differential in the 'hi5' strain relative to the 'lo' strain (SEQ ID NOS:24-258). The majority of differentially expressed sequences were unidentified ESTs. Some corresponded to previously cloned Drosophila genes and others were homologous to genes cloned in other species. Examples of genes with particular significance for human gravity response are shown in Table 4 below, and a complete list of all differentially expressed genes is included in Figure 2. These results demonstrate that at least 265 genes can be differently expressed in flies that demonstrate negative geotaxis relative to flies that demonstrate positive geotaxis. Table 4 EXAMPLE IV This example demonstrates determination of the effects of gene expression levels on geotaxis behavior in flies by artificially manipulating expression levels of genes previously identified to differ in expression level between v hi5' and Λ lo' strains. Expression of prospero (SEQ ID NO: 15) and Pigmen t-dispersing-f actor (SEQ ID NO:3), were both found to be reduced in the negatively geotactic 'hi5' strain compared to the x lo' strain. Flies containing pros 17 which is a mutant allele of prospero (SEQ ID NO:15), which has been described in Doe et al., Cell 65:451-464 (1991), were obtained from the Drosophila Stock center at Indiana University at Bloomington. Flies containing Pdf 01 (SEQ ID NO: 261) which is a mutant allele of Pigment- dispersing-f actor (SEQ ID NO: 3) and flies containing a transgenic chromosome bearing a copy of the Pigment- dispersing-f actor (SEQ ID NO: 3) locus were obtained from Dr. Paul Taghert at Washington University, St. Louis and are described in Renn et al., Cell 99:791-802 (1999). Flies containing pros 17 and Pdf 01 (SEQ ID NO: 261) were tested for alterations in geotactic behavior as described in Example I. Results of geotaxis assays are shown in Table 5. Table 5 As shown in Table 5, geotaxis score increases as the copy number of the mutant Pdf 01 (SEQ ID NO: 261) allele increases. Geotaxis score decreases as the copy number of the normal Pigment-dispersing- factor (SEQ ID NO: 3) increases. Further, as shown in Table 5, flies bearing both the Pdf 01 (SEQ ID NO: 261) and pros 17 alleles have an increased geotaxis score compared to flies bearing a single Pdf 01 (SEQ ID NO: 261) allele or single pros 17 allele. These results demonstrate that artificially manipulating the expression levels of Pdf, can convert a normal, geotactically neutral, lab strain (Canton-S) into a negatively geotactic strain. This example also demonstrates that titration of the gene dosage of Pdf titrates the geotactic phenotype such that lower amounts of gene product produce increasingly negative geotactic behavior. These results further demonstrate that prospero and Pigment-dispersing- factor operate in a network influencing geotactic behavior in invertebrates. Throughout this application various publications have been referenced. The disclosure of these publications in their entireties are hereby incorporated by reference in this application in order to more fully describe the state of the art to which this invention pertains.

Claims: We Cla im : 1. A method of identifying a compound that modulates a mammalian vestibular system comprising: (a) administering a test compound to an invertebrate, and (b) measuring a geotactic behavior of said invertebrate, a compound that modulates the geotactic behavior of said invertebrate is characterized as a compound that modulates a mammalian vestibular system. 2. The method of claim 1, wherein said compound increases the geotactic behavior of said invertebrate. 3. The method of claim 2, wherein said compound increases or decreases the sensitivity of a mammalian vestibular system. 4. The method of claim 3, wherein said compound decreases graviperception in a mammal. 5. The method of claim 1, wherein said compound decreases the geotactic behavior of said invertebrate. 6. The method of claim 5, wherein said compound increases or decreases the sensitivity of a mammalian vestibular system. 7. The method of claim 6, wherein said compound decreases graviperception in a mammal. 8. The method of claim 1, wherein said compound decreases the symptoms of a graviperceptive disorder in a mammalian subject. 9. The method of claim 8, wherein said graviperceptive disorder is selected from the group consisting of motion sickness, vertigo, labyrinthitis, Meniere's disease, acoustic neuroma, multiple sclerosis, syphilis, trauma, infection of the middle ear, exposure to ototoxic agents and epilepsy. 10. The method of claim 1, wherein said compound modulates the expression or activity of one or more mammalian proteins. 11. The method of claim 10, wherein said one or more mammalian proteins are expressed in a mammalian vestibular system. 12. The method of claim 1, wherein said invertebrate is an insect. 13. The method of claim 1, wherein said invertebrate is Drosophila melanogaster. 14. The method of claim 1, wherein said mammal is human. 15. A method of identifying a compound that modulates a mammalian vestibular system comprising: (a) administering a test compound to a test invertebrate; (b) measuring gene expression levels in said test invertebrate; (c) comparing an expression level of one or more genes in said test invertebrate relative to an expression level of one or more genes in a reference invertebrate, wherein a compound that has the effect of modulating the expression level of one or more genes associated with invertebrate geotactic behavior in said test invertebrate relative to said reference invertebrate is characterized as a compound that modulates the mammalian vestibular system. 16. The method of claim 15, wherein said compound that has the effect of modulating the expression level of one or more genes associated with invertebrate geotactic behavior in said test invertebrate relative to said reference invertebrate is characterized as a compound that modulates the expression levels of one or more mammalian genes. 17. The method of claim 16, wherein said one or more mammalian genes are selected from the group consisting of α-tectorin, gp330, PIN, SV2, PROX1, actin- binding double-zinc-finger protein, SCA2 and APP-binding protein. 18. The method of claim 16, wherein said compound increases the expression level of one or more mammalian genes selected from the group consisting of α- tectorin, gp330, PIN, SV2. 19. The method of claim 16, wherein said compound decreases the expression level of one or more mammalian genes selected from the group consisting of PROX1, actin-binding double-zinc-finger protein and SCA2. 20. The method of claim 15, wherein a compound that has the effect of decreasing expression of a specific gene in said test invertebrate relative to said reference invertebrate is characterized as a compound that increases or decreases the sensitivity of the mammalian vestibular system. 21. The method of claim 20, wherein said compound decreases graviperception in a mammal. 22. The method of claim 15, wherein a compound that has the effect of increasing expression of a specific gene in said test invertebrate relative to said reference invertebrate is characterized as a compound that increases or decreases the sensitivity of the mammalian vestibular system. 23. The method of claim 22, wherein said compound decreases graviperception in a mammal. 24. The method of claim 15, wherein said compound decreases the symptoms of a graviperceptive disorder in a mammalian subject. 25. The method of claim 24, wherein said graviperceptive disorder is selected from the group consisting of motion sickness, vertigo, labyrinthitis, Meniere's disease, acoustic neuroma, multiple sclerosis, syphilis, trauma, infection of the middle ear, exposure to ototoxic agents and epilepsy. 26. The method of claim 15, further comprising the step of (d) measuring gene expression levels in said reference invertebrate, wherein no test compound was administered to said reference invertebrate . 27. The method of claim 15, wherein said test invertebrate exhibits substantially the same geotactic behavior as said reference invertebrate before said compound is administered. 28. The method of claim 15, wherein, before said compound is administered, said test invertebrate exhibits a geotactic behavior different than a geotactic behavior exhibited by said reference invertebrate. 29. The method of claim 15, wherein said test invertebrate exhibits substantially the same geotactic behavior as said reference invertebrate after said compound is administered. 30. A method of identifying a compound that modulates a mammalian vestibular system comprising: (a) administering a test compound to a test invertebrate; (b) measuring gene expression levels in said test invertebrate, and (c) comparing the expression level of one or more genes in said first invertebrate relative to a second invertebrate, wherein a compound that modulates the expression profile of one or more genes comprising a sequence selected from the group consisting of SEQ ID NOS: 1-261 in said first invertebrate relative to said second invertebrate is characterized as a compound that modulates the mammalian vestibular system. 31. The method of claim 30, wherein a mammalian gene comprises a nucleic acid sequence substantially the same as said one or more genes comprising said sequence selected from the group consisting of SEQ ID NOS: 1-261. 32. The method of claim 30, wherein a compound that has the effect of decreasing expression of a specific gene in said test invertebrate relative to said reference invertebrate is characterized as a compound that increases or decreases the sensitivity of the mammalian vestibular system. 33. The method of claim 32, wherein said specific gene in said test invertebrate is selected from the group consisting of SEQ ID NOS: 1-23. 34. The method of claim 33, wherein said compound decreases graviperception in a mammal. 35. The method of claim 30, wherein a compound that has the effect of increasing expression of a specific gene in said test invertebrate relative to said reference invertebrate is characterized as a compound that increases or decreases the sensitivity of the mammalian vestibular system. 36. The method of claim 35, wherein said specific gene in said test invertebrate is selected from the group consisting of SEQ ID NOS:24-258. 37. The method of claim 36, wherein said compound decreases graviperception in a mammal. 38. The method of claim 30, wherein said compound decreases the symptoms of a graviperceptive disorder in a mammalian subject. 39. The method of claim 38, wherein said graviperceptive disorder is selected from the group consisting of motion sickness, vertigo, labyrinthitis, Meniere's disease, acoustic neuroma, multiple sclerosis, syphilis, trauma, infection of the middle ear, exposure to ototoxic agents and epilepsy. 40. A method of identifying a gene that modulates a mammalian vestibular system comprising: (a) obtaining a first and a second strain of an invertebrate; (b) subjecting said first and second invertebrate strains to conditions in which said first strain exhibits a geotactic behavior different than a geotactic behavior exhibited by said second strain; (c) measuring gene expression levels in said first and second strains, and (d) identifying one or more genes that are differentially expressed in said first strain relative to said second strain, whereby a mammalian gene comprising substantially the same nucleic acid sequence as said one or more differentially expressed genes modulates the mammalian vestibular system. 41. The method of claim 40, wherein said mammalian gene comprises a nucleic acid sequence substantially the same as a nucleic acid sequence selected from the group consisting of SEQ ID NOS: 1-261. 42. The method of claim 40, wherein decreased expression of said mammalian gene increases or decreases the sensitivity of the mammalian vestibular system. 43. The method of claim 42, wherein said mammalian gene comprises a nucleic acid sequence substantially the same as a nucleic acid sequence selected from the group consisting of SEQ ID NOS: 1-23. 44. The method of claim 40, wherein increased expression of said mammalian gene increases or decreases the sensitivity of the mammalian vestibular system. 45. The method of claim 44, wherein said mammalian gene comprises a nucleic acid sequence substantially the same as a nucleic acid sequence selected from the group consisting of SEQ ID NOS:24-258. 46. The method of claim 40, wherein increased expression of said mammalian gene decreases the symptoms in a mammal of a disorder selected from the group consisting of motion sickness, vertigo, labyrinthitis, Meniere's disease, acoustic neuroma, multiple sclerosis, syphilis, trauma, infection of the middle ear, exposure to ototoxic agents and epilepsy. 47. The method of claim 40, wherein decreased expression of said mammalian gene decreases the symptoms in a mammal of a disorder selected from the group consisting of motion sickness, vertigo, labyrinthitis, Meniere's disease, acoustic neuroma, multiple sclerosis, syphilis, trauma, infection of the middle ear, exposure to ototoxic agents and epilepsy. 48. The method of claim 40, wherein said second strain exhibits wild type geotactic behavior. 49. The method of claims 40, wherein said first strain exhibits negative geotactic behavior. 50. The method of claims 40, wherein said first strain exhibits positive geotactic behavior. 51. A method of modulating a mammalian vestibular system comprising administering to a mammalian subject an effective amount of a compound that modulates the activity or expression of a protein selected from the group consisting of α-tectorin, gp330, PIN, SV2, PROX1, actin-binding double-zinc-finger protein, SCA2 and APP- binding protein. 52. The method of claim 51, wherein one or more symptoms of a graviperceptive disorder in said mammalian subject are decreased. 53. The method of claim 52, wherein said graviperceptive disorder is selected from the group consisting of motion sickness, veritgo, labyrinthitis, Meniere's disease, acoustic neuroma, multiple sclerosis, syphilis, trauma, infection of the middle ear, exposure to ototoxic agents and epilepsy. 54. The method of claim 51, wherein one or more symptoms of a graviperceptive disorder in said mammalian subject are prevented. 55. The method of claim 54, wherein said graviperceptive disorder is selected from the group consisting of motion sickness, veritgo, labyrinthitis, Meniere's disease, acoustic neuroma, multiple sclerosis, syphilis, trauma, infection of the middle ear, exposure to ototoxic agents and epilepsy. 56. A method of modulating a mammalian vestibular system comprising administering to a mammalian subject an effective amount of a compound that modulates the activity or expression of a protein comprising substantially the same amino acid sequence as an amino acid sequence encoded by a nucleic acid sequence selected from the group consisting of SEQ ID NOS: 1-261. 57. A method of modulating a mammalian vestibular system comprising administering to a mammalian subject an effective amount of a compound that modulates the activity or expression of a protein encoded by a nucleic acid sequence comprising substantially the same nucleic acid sequence as a nucleic acid sequence selected from the group consisting of SEQ ID NOS: 1-261. 58. A method of modulating invertebrate geotactic behavior comprising administering to an invertebrate an amount of a compound effective to modulate the activity or expression of a protein encoded by a nucleic acid sequence comprising a nucleic acid sequence selected from the group consisting of SEQ ID NOS.1-261. 59. An isolated nucleic acid having mammalian vestibular system-modulating activity, or fragment thereof, comprising substantially the same nucleic acid sequence as a nucleic acid selected from the group consisting of SEQ ID NOS:l-261. 60. An isolated polypeptide having mammalian vestibular system-modulating activity, or fragment thereof, comprising substantially the same amino acid sequence as an amino acid sequence encoded by a nucleic acid sequence selected from the group consisting of SEQ ID NOS.1-261. 61. An antibody specific for the isolated polypeptide of claim 60. 62. The antibody of claim 61, wherein said antibody is a monoclonal antibody. 63. The antibody of claim 61, wherein said antibody is a polyclonal antibody.

Inventors: GREENSPAN RALPH J, GREENSPAN, RALPH, J.
Applicants: GREENSPAN RALPH J, NEUROSCIENCES RES FOUNDATION I, GREENSPAN, RALPH, J., NEUROSCIENCES RESEARCH FOUNDATION, INC.
Application year: 2000
Main classification: C12Q1
IPC codes: A61K38, A61K49, A61P27, C07K14, C07K16, C12N15, C12Q1, G01N33