Ion Channel Function in Auditory & Vestibular Hair Cells

描述(由申请人提供)：这里提出的研究集中在几个不同的、但同样重要的内耳研究领域。总体目标是确定感觉毛细胞中负责在耳朵中产生和传播感觉信息的基因和蛋白质。将要研究的每个基因家族都与遗传性人类疾病有关，每个家族的成员都在内耳毛细胞中表达。我们将研究的一些基因在突变时会导致耳聋和/或平衡障碍。其他的是候选耳聋基因，因为它们在毛细胞中表达，而且这些基因的已知突变会导致身体其他组织的功能障碍。因此，候选基因的突变可能会导致以前未被识别的遗传性听觉和前庭功能障碍。总的来说，我们的目标是了解毛细胞的三个关键功能，并确定支持这些功能的基因和蛋白质。1)我们将研究决定毛细胞静息潜力的离子通道基因。因为这些蛋白质在静止时是活跃的，即在没有刺激的情况下，它们对毛细胞如何对刺激做出反应有重大影响。我们想要准确地确定哪些离子通道基因参与了这一功能，并选择了三个家族进行研究：KCNQ家族、HCN家族和Kir2家族。KCNQ基因突变会导致耳聋和癫痫，而HCN和Kir2基因突变会导致心脏问题。这些家族中的每一个成员都在毛细胞中表达，但它们对毛细胞电导和毛细胞功能的确切贡献尚未确定。2)我们还对毛细胞中调节感觉适应的基因感兴趣。毛细胞对持续的毛束偏转做出反应，这导致它们的反应下降。分子马达，可能是肌球蛋白分子，已经被假设在这一功能中发挥作用。此外，肌球蛋白家族中几个成员的突变会导致耳聋。我们将特别关注一种肌球蛋白，肌球蛋白1c，并使用化学遗传策略来抑制其功能。我们将转向发束并测量它们的反应，以确定肌球蛋白1c对听觉毛细胞适应的贡献。3)最后，我们有兴趣确定哪些分子有助于毛细胞中感觉传导的发育和再生。我们推测，肌球蛋白和钙粘附素家族可能参与了这一功能。这两个家族成员的突变都会导致亚瑟氏综合征，其特征是耳聋和失明。我们将利用肌球蛋白和钙粘附素功能的慢性抑制来研究这些家族成员在感觉毛细胞转导复合体的发育和再生中的特殊贡献。通过这三条线的研究，我们的目标是确定几个有助于毛细胞正常功能的分子。由于这些关键功能的缺陷会导致耳聋和平衡障碍，通过这些研究获得的信息将有助于设计合理的策略来治疗遗传性内耳疾病。这个项目将研究遗传性耳聋和平衡障碍的一些遗传原因。我们将研究通过人类基因组计划确定的大约26,000个基因中的少数几个，我们怀疑这些基因对正常的听力和平衡至关重要。我们希望这个项目能提供一些信息，为未来制定治疗耳聋和平衡问题的策略奠定基础。美国有大约2800万内耳疾病患者。

DESCRIPTION (provided by applicant): The studies proposed here focus on several distinct, yet equally significant lines of inner ear research. The overall goal is to identify the genes and proteins in sensory hair cells that are responsible for the generation and propagation of sensory information in the ear. Each family of genes that will be investigated is associated with inherited human disease and members of each family are expressed in inner ear hair cells. Some of the genes we will investigate are known to cause deafness and/or balance disorders when mutated. Others are candidate deafness genes because they are expressed in hair cells and because known mutations in those genes cause dysfunction in other body tissues. As such, mutations in the candidate genes may cause previously unrecognized forms of genetic auditory and vestibular dysfunction. Broadly, we aim to understand three critical hair cell functions and identify the genes and proteins that underlie those functions. 1) We will examine ion channel genes that determine the hair cell resting potential. Because these proteins are active at rest, i.e., in the absence of stimulation, they have a major impact on how hair cells respond to stimulation. We want to identify exactly which ion channel genes contribute to this function and have selected three families for investigation: the KCNQ family, the HCN family and the Kir2 family. Mutations in KCNQ genes cause deafness and epilepsy, while mutations in HCN and Kir2 genes cause cardiac problems. Members of each of these families are expressed in hair cells, but their precise contributions to hair cell conductances and hair cell function have not been determined. 2) We are also interested to identify the genes that mediate sensory adaptation in hair cells. In response to sustained hair bundle deflections, hair cells adapt which results in a decline in their response. Molecular motors, probably myosin molecules, have been hypothesized to play a role in this function. Furthermore, mutations in several members of the myosin family cause deafness. We will focus on one myosin in particular, Myosin 1c, and use a chemical-genetic strategy to inhibit its function. We will deflect hair bundles and measure their response to determine the contribution of Myosin 1c to adaptation in auditory hair cells. 3) Lastly, we are interested to identify the molecules that contribute to the development and regeneration of sensory transduction in hair cells. We hypothesize that the myosin and cadherin families may contribute to this function. Mutations in members of both families cause Usher's syndrome, characterized by deafness and blindness. We will use chronic inhibition of myosin and cadherin function to investigate the specific contributions of members of these families to development and regeneration of the transduction complex in sensory hair cells. Through these three lines of research we aim to identify several molecules that contribute to normal function of hair cells. Because deficiencies with these critical functions cause deafness and balance disorders, the information gained through these studies will facilitate design of rational strategies to treat genetic inner ear disorders. This project will study some of the genetic causes of inherited deafness and balance disorders. We will investigate a handful of genes, of the approximately 26,000 identified through the human genome project, that we suspect are critical for normal hearing and balance. We expect that this project will produce information that will form the basis for development of future strategies to treat deafness and balance problems in some of the ~28 million Americans who suffer from inner ear disorders.