Paul A. Fuchs - US grants

This is a competing renewal application to continue study of the mechanism of cholinergic inhibition of cochlear hair cells using biophysical and molecular genetic analyses. We will also examine the developmental regulation of this response. Efferent axons arising from cells in the brainstem provide an inhibitory input to outer hair cells in the mammalian and avian cochleas. This inhibitory effect is thought to result from the release of acetylcholine (ACh) from the efferent endings. Several lines of evidence point to the fact that the cholinergic response of cochlear hair cells is mediated by a structurally and functionally unique ACh receptor (AChR). We propose to study the cholinergic response of hair cells isolated from the cochlea of the chick in an effort to understand the cellular and molecular bases of this inhibition. In addition, we intend to study the developmental acquisition of sensitivity to ACh in order to learn what factors govern the selective expression of these receptors in outer hair cells in adults. The experiments to meet these goals will be largely electrophysiological in nature, reflecting the established expertise of this laboratory. These will include whole-cell, cell-attached and excised patch voltage-clamp recordings. Also, we will use fluorescence microscopy of intracellular signals from Ca-indicator dyes in order to assess the role of Ca as a second messenger in the hair cell response to ACh. The initial goal of our experiments in molecular biology will be to identify the genes coding for the subunits of the hair cell AChR. We will first use low-stringency homology screening of a chick's cochlear cDNA library to identify transcripts with some relatedness to known AChRs. Expression of identified clones in hair cells will be examined by in situ hybridization and potentially by reverse transcriptase polymerase chain reaction amplification. Functional reconstitution studies will be performed by injection of cRNA into Xenopus oocytes. The developmental acquisition of AChRs by hair cells will be studied during the last 10 days of embryogenesis, that is, preceding and spanning the time that efferent axons make calyciform synapses in the cochlea. Initially we will ask whether there are parallel changes in the appearance of identified mRNAs and hair cell sensitivity to ACh. Antisense RNA will be used to block expression of identified gene products. The motivation for this study is multi-part: to understand better the mechanisms of cochlear inhibition, to contribute to the study of the molecular biology and biophysics of AChRs, and to begin to study the factors governing the developmental maturation of hair cell sensitivity to ACh.

DESCRIPTION(adapted from applicant's abstract): This application calls for the continued study of excitability and synaptic function in mechanosensory hair cells of the chicken inner ear, especially concerning the role of voltage-gated ion channels. A new venture will involve extending these efforts to hair cells of the mouse cochlea. The regulated expression of voltage-gated calcium channels supports transmitter release, while associated calcium-activated (BK) potassium channels help to shape the receptor potential arising during transduction. The proposal seeks to understand the mechanisms that contribute to ion channel function and their role in synaptic transmission by the hair cell. The investigators will continue to probe the molecular composition of BK potassium channels in chick hair cells. They suggest that both alternative splicing of the alpha subunit, and modulation by accessory beta subunits contribute to the cell-specific kinetics of these channels. Thus, the investigators will seek further evidence for the differential distribution of beta subunits and of alpha subunits splice unit variants in the mature and developing cochlea of the chick. Single channel recording will be used to determine if the gating of native BK channels is consistent with the known influence of the beta subunit. Histological techniques and quantitative RT-PCR will be used to chart the distribution and development of specific alpha and beta channel subunits. This application also proposes extend the studies to mammalian hair cells by making voltage clamp recordings in an excised preparation of the mouse cochlea. The investigators will examine the genesis of spontaneous activity in neonatal spiral ganglion neurons, characterize the biophysics and pharmacology of synaptic currents in afferent neurites at the bases of inner hair cells, quantify the relationship between hair cell calcium current and transmitter release, and determine how that varies with cochlear position and developmental age. These studies promise to further our understanding of the molecular physiology of cochlear hair cells. Further, the regulated expression of ion channels provides a window into the mechanisms that determine hair cell differentiation. The inclusion of the mouse model in this work tests the generality of these mechanisms among vertebrates, and provides an essential basis for the implementation of such studies in transgenic animals.

This is a competing renewal application from the Center for Hearing and Balance at Johns Hopkins University School of Medicine for a Research Core Grant from the National Institute for Deafness and Other Communication Disorders. The Center includes 16 investigators drawn from the Departments of Otolaryngology-Head and Neck Surgery, Biomedical Engineering, Neuroscience, Neurology, and Molecular Biology and Genetics. These laboratories provide a Research Base of 20 R01 awards, 14 of them from the NIDCD, with scientific aims ranging from the molecular biophysics of hair cells to behavioral assays of hearing and balance. Three Research Cores are proposed that will facilitate ongoing research and stimulate new initiatives at the interface between existing programs. 1. The Engineering Core will develop and distribute advanced data acquisition and signal analysis software, and provide general hardware and software support for Center laboratories. 2. The Histology Core will provide technical assistance and material support for light and electron microscopic studies, including access to microtomes and cryotomes for Users. Ultra-thin sectioning and EM analysis will be provided by a half-time senior histologist. Also, Users will receive guidance in tissue preparation, sectioning, and visualization techniques. Fluorescence microscopy will be available through a fluorescence microscope and digital imaging station in the Core. 3. The Neurophysiology Core will develop and distribute advanced CMS recording methods for use in freely-behaving animals. Indwelling multi-electrode arrays will be implemented and applied with the assistance of Core staff. 4. In addition, an Administrative unit will oversee operations throughout the Cores, organize the Center's speakers program, provide clerical and personnel support, and prepare reports.

[unreadable] DESCRIPTION (provided by applicant) [unreadable] Recent years have seen important developments in the study of hearing, especially the emergence of molecular genetics to probe the underlying mechanisms of hearing loss. It is estimated that 1 in every 1,000 newborns is profoundly deaf, while nearly 1 in 20 has a significant hearing impairment. In more than half of these cases, the cause is genetic. As of February 2002, twenty-nine specific genes have been associated with different forms of nonsyndromic human deafness. In addition, many other gene products involved in normal cochlear function have been identified. The foreign collaborator (Elgoyhen) cloned and characterized two novel nicotinic receptor genes (alpha 9 and alpha 10) that are expressed in cochlear hair cells. Alpha 9 and 10 encode receptor proteins that mediate the effect of acetylcholine (ACh) released by efferent neurons onto cochlear hair cells. The Principal Investigator (Fuchs) showed that calcium entry through the ACh receptor leads to hair cell hyperpolarization, reducing transmitter release to cause a loss of tuning and sensitivity in the auditory nerve fibers. This FIRCA proposal brings together the expertise of the Fuchs and Elgoyhen laboratories to conduct a series of electrophysiological and molecular genetic experiments to elucidate the properties and function of these cholinergic receptors in hair cell physiology. The long-term goal of this proposal is to define the physiological role of the hair cell's cholinergic receptor. In addition, it is expected that the results obtained will contribute to our understanding of the role of efferent cholinergic input in the genesis and potential treatment of hearing impairment produced by loud sound or ototoxic drugs. The immediate aims of this application are three-fold: first, the pharmacological and physiological comparison of recombinant alpha9/alpha10 receptors expressed in Xenopus laevis oocytes with native cholinergic receptors of inner and outer hair cells in acute cochlear explants; second, the characterization of the ontogeny of cholinergic responses in inner hair cells and third, the physiological analysis of synaptic contacts onto inner and outer hair cells in mice with genetic modifications in the Acra9 gene, namely the alpha9 null mutant mouse and a knock-in mouse bearing a gain of function mutation. This research will be done primarily in Argentina at INGEBI (National Research Council) in collaboration with Ana Belen Elgoyhen as an extension of NIH grant #R01 DC01508. [unreadable] [unreadable]

[unreadable] DESCRIPTION (provided by applicant): Transmitter release from vertebrate hair cells occurs at ribbon synapses where glutamate-containing vesicles fuse with the plasma membrane upon a rise in cytoplasmic calcium. Voltage-sensitive calcium channels are gated by receptor potentials to cause transmitter release that then triggers action potentials. Remarkably, in the mammalian cochlea each afferent neuron makes a single postsynaptic contact with an inner hair cell, where usually a single ribbon provides the requisite glutamate release. Thus, throughout the lifetime of the organism, a single ribbon synapse is responsible for signaling all that neuron can report to the brain concerning the frequency, timing and intensity of sound, including spontaneous activity as high as 100 Hz in the absence of sound! How does an individual ribbon carry out this task? Recent synaptic recordings from single afferent dendrites have suggested that the gating of single VGCCs is critical for information transfer at the ribbon synapse. Hair cell VGCCs are dihydropyridine-sensitive, rapidly gating at relatively negative membrane potentials, and show little inactivation in most studies. There is good evidence that the majority of VGCCs in mammalian inner hair cells contain the Cav1.3 (a1D) pore-forming subunit. However, heterologous expression of that gene product results in channels whose properties differ variously from those of the native hair cell VGCCs. Most notably, the cloned channel shows robust calmodulin-dependent calcium inactivation. Several possibilities exist to explain this difference, including alternative splicing of Cav1.3 mRNA in hair cells, and combination with various modulatory proteins. In this proposal we will combine the expertise of three laboratories to examine these possibilities. Dr. Tuck Wah Soong will use his technique of exon-scanning to characterize alternative splicing in cochlear hair cells. Dr. David Yue will apply his knowledge to develop further hypotheses of calmodulin and calmodulin-like protein modulation of hair cell VGCCs. The Fuchs laboratory will complete basic descriptions of GDI in cochlear hair cells, provide materials for gene-amplification by Soong, and together with Yue and Soong, employ new molecular tools in to alter native VGCCs in hair cells. The steady-state and dynamic gating of VGCCs will be determined by the balance of calcium-dependent inactivation and opposing mechanisms. Our ultimate aim will be to derive the contribution of VGCC gating to hair cell information transfer. [unreadable] [unreadable] [unreadable]

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DESCRIPTION (provided by applicant): The goal of our program is to train and to develop outstanding physician-scientists in otolaryngology- head and neck surgery. Our specialty requires multidisciplinary approaches for the understanding and treatment of communication disorders and diseases of the head and neck. In order to meet this objective, our residents need to be educated in both clinical and research skills. Research training is a key element to our training program because it serves as a means to enhance critical thinking and communication skills, to strengthen the understanding of scientific and medical literature, to provide training in investigative techniques, and to develop the ability to pose testable hypotheses. One outstanding feature of our current training program is that each year, two residents embark on 2 years of continuous research training where research opportunities include, but are not limited to, topics in molecular biology of head and neck cancers, basic mechanisms of dizziness and balance, studies of the auditory nervous system, cell and tissue engineering and clinical outcomes. The strength of this training plan is measurable by the breadth and experience of the involved faculty. The success of the training program is evident in the accomplishments of those otolaryngologists who have completed their training on this sequence and who are now building successful academic careers.

DESCRIPTION (provided by applicant): This is a proposal to determine the functional properties of till-now-mysterious type II afferents of the mammalian cochlea. Although comprising only a small fraction (5-10%) of all cochlear afferents, their unique arborization to outer hair cells, and termination pattern in the auditory brainstem strongly imply a functional role quite distinct from that of the type I afferents. Limited data suggest that type II afferents have a very high acoustic threshold, perhaps signaling only traumatic or painful levels of sound. Further extending an analogy to somatic pain fibers, type II afferents are activated by ATP that can be released during cochlear trauma, as it is in damaged skin. This project will involve giga-ohm-seal intracellular recording from type II afferents in cochlear segments ex vivo to characterize the excitability and synaptic function of type II afferents. Basic membrane properties, action potential threshold and initiation site, and the size and distribution of synaptic inputs will be determined. Quantal analysis will determine outer hair cell synaptic strength. Pre- and postsynaptic structures associated with recorded fibers will be immunolabeled posthoc. These data will be incorporated into an anatomically-correct, compartmental model to obtain an estimate of the acoustic stimulus required to activate the type II afferent. To explore further a possible role in cochlear trauma, type II recordings will be made in cochleae that have been damaged by loud sound and/or exposure to ototoxins. Hearing loss can lead to hyperacusis and the phantom percept of tinnitus. The analogy to peripheral sensitization and 'phantom limb pain' prompts parallels with somatic neuropathy. Delineation of the functional role of type II afferents adds essential, long-missing information on cochlear function that will enhance theories of auditory pathogenesis, and may provide new therapeutic targets.

Research Strategy: Significance: The Administrative Shell of the Sensory Mechanisms Research Core Center will support and foster close interactions among Core Center Directors, Core Users, central Administration and other elements of the Johns Hopkins University through a number of active mechanisms and already existing relationships. Both the Center for Hearing and Balance, and the Center for Sensory Biology involve their members in academic programs, regular research meetings, and fund-raising efforts. The Center for Hearing and Balance maintains a T32 graduate student and postdoctoral training grant (directed by E. Young, assisted by P. Fuchs), teaches a two-semester course EN 580.625 Structure and Function of the Auditoiy and Vestibular Periphery, runs a weekly research seminar, and holds daily lunchtime gatherings of available staff. The Center for Sensory Biology holds quarteriy research colloquia, monthly 'chalk talks' by member faculty and teaches a spring semester course to Biology Department undergraduates, AS.080.322 Cellular and Molecular Biology of Sensation. Through the shared use of Histology and Engineering resources the Users lab will have a common ground for meeting and interchange. To further these interactions, the P30 will continue its 'post-ARO poster session' at which participants get another chance to see their colleagues' presentations one Thursday evening in February with pizza. Each of the Engineering and Histology Cores will have independent procedures for communication among User labs and feedback (see those sections). In addition. The P30 Directors will hold a feedback meeting each trimester at which User labs will be invited to suggest improvements to Core functions and resources. Finally, the P30 Admin Shell provides funds for 1-2 speakers each year for each of the Engineering and Histology Cores. These speakers are chosen for their novel technical and/or scientific discoveries relevant to the Core's activities. For example, previous years' series have included Lisa Olson, Bev Wright, Bechara Kachar, Isreal Nelkin, Kari Kandler and Lisa Goodrich among others. These 'special speakers' are chosen by the Core Directors specifically, but are included within the weekly Center for Hearing and Balance seminar series which members of of the User labs attend. The P30 Research Core has facilitated interdepartmental communication in a variety of ways. For example, by providing partial support for the electron microscope in the Ophthalmology department the Histology Core has fostered strongly collegial relations with members of that research group. The P30 has significant impact within the wider department of Otolaryngology-HNS. Dr. Mohamed Lehar is supported in part by Oto-HNS funds and thereby manages the temporal bone laboratory in which surgical training is conducted. He additionally assists clinician-scientists such as Drs. Howard Francis and Wade Chien who are undertaking a re-organization and digitization of the George Nager temporal bone collection. The participation of P30 faculty in the Center for Sensory Biology has particulariy wide impact on the basic sciences of the School of Medicine. Through this consortium research into inner ear and chemical senses is brought to the attention of the wider neuroscience and molecular genetics community. The Center for Sensory Biology also adds to the integration of P30 labs with School of Medicine administration, with attendant benefits. A good example is the donation of research space for the laboratory of Dr. Andy Lane in the new Ranges Research Building (he quickly outgrew his original lab en Ross 8). Although this was formally an agreement between Otolaryngology and the Institute for Basic Biomedical Sciences, the easy negotiations and rapidly-reached agreement reflected the good relations established by Fuchs and Reed with Desiderio, director of the IBBS. Finally it should be noted that P30 operations succeed in no small part through the warmly collegial relations among the directors. Fuchs, Yeung and May have enjoyed their partnership in the Center for Hearing and Balance since 1995. Fuchs and Reed worked together with other colleagues to compete for and win funding to establish the Center for Sensory Biology (CSB) in 2005. They continue their teamwork as Director (Reed) and co-director (Fuchs) of the CSB, and with fellow CSB members develop new initiatives for that program.

The Histology Core, under the co-direction of Drs. Paul Fuchs and Randy Reed, and staffed by Drs. Hakim Hiel and Mohamed Lehar, will provide training and guidance in a variety of histological procedures, as well as image acquisition and analysis using a core confocal microscope. Preparation for electron microscopy, ultrathin sectioning and image collection also will be provided. In addition to supporting those laboratories with qualifying grants, an important function of the Histology Core is to enable junior investigators to build their research programs in NIDCD-related areas. Finally, by serving as a source of expertise in inner ear and olfactory histology, the PSO enables novel disease and/or mouse models to be examined as they arise in other non-NIDCD-related research programs.

DESCRIPTION (provided by applicant): This is the application for competing renewal of P30 DC005211, Sensory Mechanisms Research Core to provide shared services to a group of NIDCD-funded laboratories. The proposal includes an Administrative Shell, Engineering and Histology Cores. These Research Cores will enable more efficient utilization of common services, as well as access to specialized expertise. The Engineering Core includes a senior programmer and electronics technician, central data servers, auditory phenotyping facility, design of advanced acoustic stimuli and analyses, and a large-format poster printer. The Histology Core offers support and training in tissue preparation for standard light microscopy and immunofluorescence. In addition the Histology Core supports a senior EM microscopist, ultramicrotomy and EM access, as well as trained histologists to guide confocal imaging. The Histology Core will incorporate a confocal microscope into the shared facilities. Together the Engineering and Histology Cores, organized through the Administrative Shell, further strengthen the Center for Hearing and Balance, and now the Center for Sensory Biology which includes NIDCD-funded laboratories studying chemical senses at Johns Hopkins.

? DESCRIPTION (provided by applicant): The proposed Training Program in Hearing and Balance will provide research training to predoctoral and postdoctoral students in the Center for Hearing and Balance. The training focuses on research on the normal and damaged auditory and vestibular systems. Research approaches include neurophysiology, human and animal behavior, theoretical and computational methods, neuroanatomy, molecular biology, genetics, and cellular physiology. The objective is to provide a multi-disciplinary program in which trainees from diverse backgrounds can gain experience with a range of methods. The training faculty are drawn from the Departments of Biomedical Engineering, Electrical and Computer Engineering, Neurology, Neuroscience, and Otolaryngology-Head and Neck Surgery at the Johns Hopkins University. The trainees will include five predoctoral students recruited from the graduate programs of Biomedical Engineering or Neuroscience and five postdoctoral fellows with appropriate doctoral degrees recruited directly to the program and appointed in one of the participating departments. At all levels, training will focus on research, taking advantage of the excellent research facilities available in the Center. Trainees participate in the weekly research seminar of the Center as well as one of the available journal clubs. The program provides a year-long core course in Hearing and Balance and specialty courses in molecular, cellular, and systems biology and in computation and theory. Predoctoral trainees generally participate for up to five years and postdoctoral trainees for two to three years.

? DESCRIPTION (provided by applicant): The canonical chemical synapse of the nervous system is characterized by electron-dense thickening of the post-synaptic membrane in close apposition to the pre-synaptic active zone. Quite distinct and far less well- understood are the so-called c-synapses named for the sub-synaptic cistern in the post-synaptic cell that is aligned with the pre-synaptic terminal. Although common on motor neurons and cerebellar Purkinje cells among others, essentially nothing is known about c-synapse function except that they are formed by cholinergic inputs. Chief among the mysteries is the role of the subsynaptic cistern itself, although its similarity to sarcoplasmic reticulum has prompted suggestions of involvement in calcium (Ca2+) signaling. The goal of this proposal is to advance understanding of c-synapse function through a combination of computational modeling coupled with experiments on the cholinergic c-synapse. A major impediment to study of c-synapses on central neurons is the fact that there is typically no means to activate them selectively out of th multitude of inputs. We will take advantage of an exemplar c-synapse that is experimentally tractable - efferent cholinergic neurons that project from the brainstem medial olivocochlear nucleus to inhibit cochlear outer hair cells (OHCs). Because this is its sole synaptic input, the OHC will provide unique insights into how c-synapses operate. First and foremost is to determine whether the cistern regulates postsynaptic Ca2+. Remarkably, c- synapses share common design features with the fundamental structural units of excitation-contraction coupling in the heart known as dyads. In each case, a Ca2+ store (junctional sarcoplasmic reticulum JSR in heart; cistern in the OHC) is positioned close (~14 nm) to the cell membrane, creating a restricted Ca2+ nano- domain. Ca2+ sources in the cell membrane (voltage-gated Ca2+ channels in heart; nicotinic cholinergic receptors nAChRs in OHCs) direct their flux into this restricted space. In OHCs, Ca2+-activated potassium type- 2 (SK2) channels are located near the nAChRs. Even small fluxes directed into the cleft can create large Ca2+ signals that are highly localized in space and time. Ryanodine-sensitive, Ca2+-binding Ca2+-release channels (RyRs) are thought to reside in the closely apposed cistern membrane as in JSR, suggesting that the process of Ca2+-induced Ca2+-release (CICR) may be important to OHC function, as it is in the heart. We will leverage these similarities to harness extensive modeling work done in the Winslow lab on CICR in the heart, adapting these models and applying them to advance our understanding of the function of c-synapses in the nervous system. Modeling work will be informed by experiments conducted in the Fuchs lab that will probe the structure and function of the OHC c-synapses. This unique combination of an experimentally-tractable system, along with the modeling and experimental expertise of these two labs, will enable us to advance our understanding of the function of c-synapses in the nervous system.

Project Summary    This proposal aims to test the hypothesis that type II afferents serve as cochlear nociceptors.  Taking cues from the human complaint of hyperacusis after hearing loss, we will examine the structure  and function of type II afferents in normal and post?trauma cochleas.  The working hypothesis is that  painful hyperacusis, noxacusis, includes hyperactivity of type II afferents, by analogy to hyperalgesia of  somatic nociceptive C?fibers.  Thus we will examine type II structure and function in normal and post?trauma  cochleas of rats and mice.  In parallel we will investigate the properties of surviving outer hair cells in post? trauma cochleas. Our methods include: ex vivo electrophysiology, light and electron microscopy, utilization  of optogenetic and chemogenetic tools, and validation and quantification of mouse models in which type II  specific bio?markers are expressed.    A necessary first step is to extend our ex vivo experimental approach to older cochleas so that  changes wrought by acoustic trauma can be compared to the normal condition.  We will compare  damaging sound, ototoxic antibiotics and genetically encoded biotoxins to produce experimentally  tractable effects on tissue for ex vivo experiments.  The properties and synaptic connections of type II  afferents and outer hair cells will be examined in the excised cochlear tissue of these animals.  We will  continue to explore type II specific genetic mouse models.  Genetically?encoded reporter proteins,  voltage? and calcium?sensitive indicators, biotoxins, and opto? and chemo?genetic modulators have  become highly informative tools in neurobiology generally and for the inner ear specifically.  Our  ongoing work has characterized one mouse line, tyrosine hydroxylase promoter driven Cre?recombinase  expression.   Three other candidate type II specific Cre lines will be validated and quantified.  With such  transgenic models it becomes possible to study innervation patterns by expression of fluorescent  reporter proteins, and to activate, eliminate, or modulate type II activity for anatomical and physiological  studies. Cre?dependent expression of genetically?modified G?protein?coupled receptors (DREADDS) will  provide mice in which type II activity can be increased or decreased by injection of a novel synthetic  ligand, depending on the specific construct.  Varying combinations of systemic and round window drug  delivery will be employed to increase the specificity of experimental manipulations.      The over?arching goal of this program of experiments is to complete the description of type II  afferents, a still?unresolved component of cochlear innervation.  The working hypothesis is that these  serve as cochlear nociceptors.  If correct these are a likely neurobiological substrate for noxacusis  (painful hyperacusis).  By defining the basic cellular and molecular mechanisms of type II function and  plasticity, future therapeutic targets can be identified to ameliorate or prevent noxacusis. 

This research proposal examines the impact of acoustic trauma, development and aging on the innervation of cochlear hair cells, with particular focus on the role of the efferent system. Emerging evidence suggests that afferent and efferent synapses interact in undefined ways during a developmental critical period, and in parallel with altered acoustic function. How might such interactions occur? Does activity of the hair cell determine synaptic arrangements, or do synapses ?compete? for territory? In particular, do efferent inputs play an instructive role in the differentiation of hair cell function? Or, are efferent (and afferent) synapses dependent upon changes in hair cell excitation? To approach these questions, hair cell excitability and synaptic function will be detailed before and after acoustic trauma in AChR-null (?9 null) mice, and in those with gain of function AChRs (?9L9?T). Auditory function and synaptopathy will be assessed in aging animals in ?9 null and ?9L9?T mice. Finally, the developmental maturation of synapses on IHCs will be examined in TMC2 mechanotransduction null mice.

Summary/Abstract This is an application for renewal of T32 DC000023, ?Research Training in Hearing and Balance? to the Center for Hearing and Balance (CHB) at Johns Hopkins University in Baltimore, Maryland. Pre-doctoral (4) and postdoctoral (4) training slots are requested. The interdepartmental Center for Hearing and Balance brings together expertise from across the Johns Hopkins University to inspire and promote research into basic mechanisms of hearing and balance, pathogenesis and innovative therapeutic strategies. While training opportunities are widespread and deep within each of the home departments, the mission of the Center is to provide a common knowledge base and technical expertise for trainees to advance their hearing and balance-related research goals. Research progress at all levels from molecular genetic to public health depends on well-trained investigators who are knowledgeable about hearing and balance from peripheral mechanisms to behavioral consequences. To accomplish that goal, auditory and vestibular studies employ integrated knowledge from engineering, biology and behavior. The training faculty of this T32 spans that wide range of knowledge and expertise and so uniquely prepares pre- and postdoctoral trainees at Hopkins for this field. The inclusion of a strong cohort of clinician-scientists ensures that trainees will understand the relationship of their research training to health and disease.