Functional development of hair cells

描述（由申请人提供）：内耳的毛细胞具有将头部运动和声音转换为电信号并传输到大脑的独特作用。毛细胞如何完成这一独特的功能一直是集中和富有成效的调查在过去的四分之一世纪。一些分子的球员已经确定，但身份的转导通道本身和许多相关的转导复合物仍然难以捉摸。毛细胞转导复合物的分子鉴定的滞后是每个感觉器官的毛细胞数量少（2-16千）和每个细胞的转导分子少（50-100）的结果。为了规避这些困难，我们提出了一种新的和令人信服的方法，将利用精确的时间和区域的发展模式，在小鼠耳蜗中的机械转导收购。在这个项目的第一部分，我们将确定毛细胞成为机械敏感的功能，发育阶段和位置沿着耳蜗，我们将表征tonotopic差异的机械转导的属性。我们假设毛细胞机械感觉所需的基因将在转导开始的时候富集。因此，我们将分析各种候选分子在Corti器官发育过程中基因表达的时空模式。具有与机械敏感性获得模式平行的表达模式的分子将被鉴定为转导候选物。为了确定候选分子的确切作用，我们将抑制它们的功能表达，并使用体外和体内试验来破坏毛细胞和听觉功能。特别地，我们将使用RNA干扰和显性负抑制并测定发育中毛细胞中机械转导的抑制。为了检查体内基因功能，我们将产生突变候选基因的诱导型毛细胞表达，并测定听觉功能的丧失。本研究旨在确定耳聋和平衡障碍的遗传基础。我们将检查正常内耳在发育过程中的感觉细胞，以确定细胞何时开始发挥功能，以及哪些基因被激活。我们将使用几种遗传技巧来阻断这些基因的活性，并检查它们对听力的影响。听力功能丧失将确认哪些基因是正常听力所必需的，哪些基因突变后可能导致遗传性耳聋。

DESCRIPTION (provided by applicant): Hair cells of the inner ear have the exclusive role of converting head movements and sound into electrical signals that are transmitted to the brain. How hair cells accomplish this unique function has been the focus of intense and fruitful investigation over the last quarter century. A few of the molecular players have been identified, however the identity of the transduction channel itself and much of the associated transduction complex remains elusive. The lag in molecular identification of the hair cell transduction complex is a consquence of the low number of hair cells per sensory organ (2-16 thousand) and the few tranduction molecules per cell (50-100). To circumvent these difficulties we propose a novel and compelling approach that will take advantage of the precise temporal and regional developmental pattern in the acquisition of mechanotransduction in the mouse cochlea. In the first part of this project we will determine when hair cells become mechanosensitive as a function of developmental stage and position along the cochlea and we will characterize tonotopic differences in the properties of mechanotransduction. We hypothesize that genes required for hair cell mechanosensation will be enriched around the time of transduction onset. Thus, we will analyze the spatio-temporal pattern of gene expression for various candidate molecules during the development of the Organ of Corti. Molecules with expression patterns that parallel the pattern of acquisition of mechanosensitivity will be identifed as transduction candidates. To determine the precise role of the candidate molecules we will inhibit their functional expression and use in vitro and in vivo assays for disruption of hair cell and auditory function. In particular, we will use RNA interference and dominant- negative inhibition and assay for suppression of mechanotransduction in developing hair cells. To examine gene function in vivo we will generate inducible, hair cell expression of mutant candidate genes and assay for loss of auditory function. Lay summary: This study is designed to identify the genetic basis of deafness and balance disorders. We will examine the sensory cells of the normal inner ear during development to identify when the cells begin to function and which genes are turned on. We will use several genetic tricks to block the activity of those genes and examine their effect on hearing. Loss of hearing function will confirm which genes are necessary for normal hearing and which genes may cause genetic deafness when mutated.