University of California San Francisco

The role of cochlear capsule bone remodeling in hearing loss

Although several bone diseases cause sensorineural hearing loss, the mechanism by which bony defects impair auditory function remains unclear. The long term goal of this research is to better understand the role of bone in the sensorineural function of the ear—with the objective of identifying bone targets that might be therapeutically effective in the prevention or reversal of hearing loss. The goal of this proposal is to test the hypothesis that abnormal remodeling of the cochlear capsule results in hearing loss by damaging the material quality of the cochlear bone matrix. Our recent studies on bone disease-associated hearing loss have shown that cochlear bone hardness is critical for hearing. Understanding bisphosphonate action in the ear is clinically important because drugs are commonly used to treat osteoporosis and bone disease-associated hearing loss.

University of North Carolina at Chapel Hill

Synaptic organization and plasticity in the auditory cortex following cochlear ablation: role of serotonin neurotransmission

The long-term objective of this proposal is to investigate mechanisms of plasticity in auditory cortex neurons following bilateral cochlear ablation. The evaluation of auditory cortex neuronal functioning in an animal model of deafness and the progressive identification of neurotransmitter receptor systems that may modulate their activity after hearing loss, may lead to the development of pharmacologic tools to facilitate restorative hearing.

Johns Hopkins University

Connexin involvement in spontaneous activity in the developing cochlea

Our recent studies indicate that spontaneous activity in the developing auditory nerve is initiated by the release of ATP from supporting cells in the organ of Corti. The goal of these studies is to evaluate the role of connexins in triggering ATP release from supporting cells. We propose to use electrophysiological and imaging methods in whole-mount preparations of pre-hearing cochleas to probe the sensitivity of spontaneous activity to manipulations that inhibit gap junction/hemichannel activity. We will extend these studies by testing whether expression of connexin 26 mutants associated with congenital hearing loss (R75W, W44C) alters this spontaneous activity. The studies outlined in this proposal seek to test the hypothesis that connexins play an essential role in the propagation of Ca2+ waves through the support cell network, and are responsible for the release of ATP in the developing organ of Corti.

Wayne State University School of Medicine

Nasopharyngeal biofilms in the pathogenesis of recurrent acute otitis media

Ear infections are a significant problem in infants and children. Research has shown bacteria that cause ear infections are resistant to antibiotics. By understanding which bacteria form these chronic infections and by evaluating new treatments we hope to reduce the number of children that require ear tubes. This will allow researchers to understand which bacteria form biofilms; when biofilms develop and help to better understand the role of biofilms in recurrent ear infections; and new treatment options for children with frequent ear infections.

Harvard Medical School

Genetic dissection of planar cell polarity within the inner ear

It is broadly accepted that hearing and balance requires the correct orientation of hair cells and their stereocilia bundles within the inner ear. This patterning is called planar cell polarity and involves the coordinated organization of adjacent hair cells. This project aims to understand the developmental mechanisms generating planar polarization and to determine the effects of hair cell disorganization upon auditory and vestibular function.

University of Kentucky

Mechanoelectrical transduction without Myosin XVa

The long-term goal is to define the molecular and biophysical mechanisms shaping mechanosensitivity in cochlear hair cells. A common structural feature of hair cells in all vertebrates is the staircase arrangement of stereocilia, which is thought to be critical for mechanotransduction. This study will determine the distinguishing features of mechanotransduction in auditory hair cells of deaf shaker 2 mice that have abnormally short stereocilia due to a mutation in the motor domain of Myosin XVa.

University of Tennessee Health Science Center

Evaluation of Stereocilia Morphology in Genotypically Math 1-null Cells in Chimeric Mice

The current time period represents an exciting one in the field of auditory functioning with the advent of stem cells and the identification of molecules that control the formation of hair cells (HCs) holding the promise of creating new HCs. One such molecule is the transcription factor Math1 that has been shown to be critical for HC generation. We have examined environmental interactions in the development of HCs and emphasize its importance in hair cell generation by showing that cells that lack Math1 can form hair cells given the correct context. However, it remains unclear whether or not these cells fully differentiate or become functional. This grant is designed to address this issue by examining the morphology of the region of the hair cell that responds to sound, the stereocilia. Analysis will determine whether this region expresses its characteristic markers in a normal manner and whether they are organized correctly. This experiment will provide useful information for further studying how the mutant HCs develop and mature in the chimeric inner ear. The use of these animals creates a system to gain further understanding of the factors that affect hair cell differentiation, knowledge essential in any corrective therapies.

Indiana University School of Medicine

Role of T1x3 signaling in inner ear sensory neuron development

The primary goal of this study is to elucidate novel functions of the Y1x3-class homeobox gene 3 (T1x3) in the development of inner ear sensory neurons. The specific aims in this study are: (1) To test whether T1x3 is required for normal development of inner ear sensory neurons, and (2) To test whether T1x3 is sufficient for multipotent progenitor cells in the early embryonic ear to become competent to commit to a glutamatergic neural subtype. The long-term goal of this study is to clearly understand the molecular mechanisms underlying specification of auditory and vestibular neurons.

New York University School of Medicine

Mouse models of human syndromic hearing loss linked to mutant MYH9 alleles

Mutations within the nonmuscle myosin heavy chain type IIA (MYH9) have been linked to human hearing loss. The study will examine the biological role of MYH9 in hearing and the role of its mutant alleles MYH9R702C in hearing loss with the goal of developing and characterizing transgenic mouse models that express the mutant alleles MYH9R702C which is linked to syndromic hereditary hearing loss in humans. Characterizing these mice models will lead to elucidation of the role of MYH9 in hearing and help to development of therapeutic strategies for circumventing hearing loss due to MYH9 mutation.

Rosalind Franklin University of Medicine and Science

Splicing regulation of pre-mRNA generated from the deafness-associated Espin gene

The goal of this proposal is to determine how Espin gene expression is controlled at the level of RNA processing. Loss of function mutational analysis will identify RNA sequences on the Espin pre-mRNA that are essential for alternative splicing reactions. Proteins that bind the regulatory RNA sequences will be identified by UV-cross- linking, Western blotting and immunoprecipitation. Correlation of the in vitro analysis with in vivo activity will be accomplished through modulating by RNAi and overexpression the levels of these proteins in HeLa cells transfected with Espin mini-gene constructs containing genomic sequence corresponding to the alternatively spliced exon and flanking introns.

University of Rochester

Cortical synaptic plasticity in a mouse model of moderate sensorineural hearing loss

The development of cortical networks is exquisitely sensitive to patterned activity elicited through sensory stimulation. Although much is known about somatosensory and visual cortical development, very little is known about the development of auditory cortex network connectivity. Changes in hearing that occur as a result of defects in sensation at the cochlea likely affect the development of higher brain areas which process auditory information. Our research will explore changes in the neural networks that process auditory stimuli in the cortex in a mouse model where prestin, a protein crucial for outer hair cell electromotile function is absent during development. We will address this question by looking at synaptic sites which link individual neurons into networks and compare their density, distribution and dynamic remodeling in control and prestin-null mice. We hypothesize that changes in both static and dynamic synaptic structure will be present in the auditory cortex of prestin-null mice, suggesting that cortical auditory networks are altered by degraded hearing during development. This work will shed light on synaptic mechanisms and possible treatments of developmentally acquired hearing loss.

Ohio University

The distribution of glutamate receptors in the turtle utricle: a confocal and electron microscope study

When stimulated by acceleration and head tilt (gravity), sensory hair cells in the turtle utricle, an organ in the inner ear, transmit information about these stimuli to the brain. The long term goal of this research is to understand what role synaptic structure and composition play in the observed spatially heterogeneous and diverse discharge properties of afferents supplying the vestibular end organs, and in particular, the utricle. This knowledge is central for accurate diagnosis and rational treatment strategies for vestibular dysfunction.

University of Michigan

Determine the functional role of the unique amino terminus of MYO15 in hearing using genetically engineered mice

Assessing the role of the N-terminus of MYO15 in structural development of hair cells and in the neurosensory process of hearing is expected to provide basic information about the process of hearing at the molecular level. Long term, we expect proteins that interact with the N-terminus of MYO15 will also be defective in some forms of hearing loss. Models similar to the one we propose have been used as proof of principle for gene therapy. Mutations in humans indicate that the N-terminal portion of MYO15 is required in some way for hearing. Using our resources and experience in genetically engineered mice will advance the understanding of the specific molecular function of the N-terminus of Myo15 in mammalian hearing and determine the consequences on morphological development and signal transduction within the cochlear hair cells. Thus, these studies will immediately make a contribution to the rapidly advancing field of molecular hearing research. The next step will be to identify the proteins that interact with the N-terminus, screen pedigrees for mutations in these genes and work towards therapeutic intervention for genes that are common causes of deafness.

University of Utah Medical School

Molecular analysis of hair cell regeneration in the zebrafish lateral line

We are aiming to elucidate the genetic pathways underlying hair cell regeneration in zebrafish with the long-term goal of activating these pathways in mammals. Our lab is taking a twofold approach to identify genes involved in hair cell regeneration. We are performing gene expression analyses from mantle cells of control larvae and from larvae in which mantle cells are proliferating to regenerate killed hair cells (as proposed in this application). As a second approach we are performing a mutagenesis screen for zebrafish mutants which are not able to regenerate hair cells, and thus carry mutations in regeneration-specific genes. A prominent cause of deafness is loss of hair cells due to age, noise or antibiotic treatments. In contrast to mammalian hair cells, fish, bird and amphibian hair cells turn over frequently and regenerate following hair cell death. Little is known why lower vertebrates are able to regenerate hair cells but humans do not. This is partly due to the relative inaccessibility of inner ear hair cells to direct observation and manipulation. Our aim is to take advantage of the lateral line of zebrafish to define and characterize the molecular and cellular interactions occurring during hair cell regeneration. If successful, our results will set the stage for testing whether hair cell regeneration can be activated in humans.

University of North Carolina Wilmington

Enhancement of the efferent-hair cell synapse by metabotropic glutamate receptors

This proposal aims to improve our understanding of the molecular mechanisms regulating synapses in the cochlea and will specifically characterize how a class of molecules, metabotropic glutamate receptors (mGluRs), regulates the efferent-hair cell synapses. Sensory hair cells of the cochlea communicate with the brain at specialized sites called synapses. Inner hair cells have numerous afferent synapses that relay information about sound from the hair cell to the brain. In contrast, outer hair cells are characterized by efferent synapses from the brain that regulate hair cell activity. Although these efferent and afferent synapses are normally considered to be independent from one another, experiments studying immature inner hair cells suggest that glutamate, the neurotransmitter required for transmission at the afferent synapse, may also modify the response of the efferent synapse. Efferent innervation of the cochlea is thought to protect against noise-induced hearing loss. Considering that noise-induced hearing loss accounts for one-third of all cases of deafness, understanding the mechanisms regulating efferent synapses is of special clinical relevance. This project will investigate this hypothesis and should uncover novel pharmaceutical targets to modulate the efferent synaptic response to either dampen hair cell activity and prevent noise-induced hearing or boost hair cell activity and combat deafness.

Baylor College of Medicine

The structural and functional basis of electromotility in prestin, the outer ear amplifier protein

Prestin, a membrane protein in outer hair cells in the cochlea, is involved in cochlear amplification leading to frequency sensitivity. The long-term objectives of this study are to understand the molecular basis of prestin function, to advance the field closer to designing therapeutics in certain types of hearing loss. This will provide insight into the molecular basis of prestin-related hearing loss, and can lead to rational design of therapeutics to treat such conditions.

Creighton University

Role of central auditory neurons in pathogenic mechanism of progressive high frequency hearing loss (PHFHL)

The long-term objective of this study is to assess the relative contribution of Central Auditory Neurons (CANs) to high frequency hearing loss. The peripheral auditory system suggests that progressive hearing loss is resultant of SGNs and/or IHCs dysfunction. This study proposes to determine the effects of the mutations using genetically engineered mice with DN-KCNQ4 expression specific to CANs. Achieving these objectives will open doors to the formulation of therapeutic modalities and possible interventions to PHFHL treatment.

Rush University Medical Center

Perception of environmental sounds and speech in patients with cochlear implants

This project will assess the ability of patients with contemporary cochlear implants to perceive environmental sounds using a new test of environmental sound perception. It will further examine the relationships between perception of environmental sounds and speech. A close association between these abilities would open an exciting possibility of developing a language-independent instrument for estimating speech perception abilities based on environmental sound tests (e.g., when speech materials are not available for some languages for potential candidates). Such a test would have highly useful clinical applications in large urban clinics or in developing countries with fledgling implant programs.

Emory University School of Medicine

The molecular diversity of gap junction channel systems in the cochlea

The long-term objective of this study is to understand how molecular mechanisms of different subtypes of connexins (Cxs) contribute to cochlear functions. Connexins (Cxs) are a family of proteins constituting the gap junctions (GJs). GJs allow direct intercellular exchanges of nutrients, inorganic ions, signaling molecules. The importance of Cxs in hearing functions has been revealed by large amount of genetic linkage studies showing that mutations in Cx genes are associated with about half of patients with childhood nonsyndromic hearing losses. Mutations in Cx26 are responsible for most of the cases. However, mutations in a myelinating Cx (Cx32) have also been linked to Charcot-Marie-Tooth syndrome that includes hearing defects in many cases. Despite their importance in hearing, we know very little about molecular mechanisms that GJs play in the cochlea.