Regulation of sensory cell specification in the developing cochlea

描述(申请人提供)：Corti器官的发育是一个严格调控的过程，耳蜗管的一个小的“前感觉域”被分成各种类型的毛细胞和支持细胞。虽然已经知道细胞间信号，如Notch和成纤维细胞生长因子，在耳蜗发育的几个步骤中都是必需的，但它们在感觉细胞特化阶段的确切作用和关系尚不清楚。在过去的一年里，我们发现FGF20对于感觉细胞的规范是必要的。抑制FGF20或抑制成纤维细胞生长因子受体导致Atoh1表达缺失。我们还发现，在耳蜗体发育的早期阶段，抑制外植体培养中的Notch信号会导致感觉细胞发育受阻。这些发现导致了一个工作模型，在该模型中，前感Notch信号导致FGF20的表达，然后FGF20激活感觉细胞中的Atoh1。在这份意见书中，我们提出了几条调查路线，旨在测试关于感觉细胞规格的分子机制的具体假设。我们的建议有以下具体目的：1.确定Notch的前感觉作用是否由FGF20介导；2.确定Notch对FGF20表达的作用是否是直接的；3.确定Ets结构域转录因子是否是感觉细胞规范所必需的和/或充分的。更好地了解调节正常发育的分子途径将是合理的成人耳聋毛细胞替代和再生策略的关键。 公共卫生相关性：了解内耳的感觉细胞是如何被指定的，是设计合理的修复策略的非常重要的第一步，以便在由于耳毒性或噪音造成的损伤后使用。这项提议旨在阐明感官细胞和相关分子发育的关键步骤。一旦确定了分子途径及其使用顺序，就可以测试在受损组织中激活或抑制这些途径的化合物，以评估它们对再生的影响。

DESCRIPTION (provided by applicant): The development of the organ of Corti is a tightly regulated process, in which a small "prosensory" domain of the cochlear duct is sorted into various types of hair cells and support cells. While it known that intercellular signals, like Notch and FGF, are required at several steps in cochlear development, their precise roles and relationship at the stage of sensory cell specification are not clear. In the past year, we have found that FGF20 is necessary for sensory cell specification. Inhibition of FGF20 or inhibition of the FGF receptors leads to a loss in Atoh1 expression. We have also found that inhibition of Notch signaling in explant cultures at early stages of cochlear development leads to a block in sensory cell development. These findings have led to a working model in which the prosensory Notch signal leads to the expression of Fgf20, which then activates Atoh1 in the sensory cells. In this submission, we propose several lines of investigation aimed at testing specific hypotheses about the molecular mechanisms of sensory cell specification. Our proposal has the following specific aims: 1. To determine whether the prosensory action of Notch is mediated by FGF20; 2. To determine whether the action of Notch on FGF20 expression is direct; 3. To determine whether Ets domain transcription factors are necessary and/or sufficient for sensory cell specification. A better understanding of the molecular pathways regulating normal development will be critical for rational strategies for hair cell replacement and regeneration in adult onset deafness. PUBLIC HEALTH RELEVANCE: Understanding how the sensory cells of the inner ear are specified is a very important first step towards designing rational repair strategies for use after damage due to ototoxicity or noise. This proposal is geared towards elucidating the key steps in development of the sensory cells and the molecules involved. Once the molecular pathways, and the order in which they are used, are established it would allow for testing of compounds that activate or inhibit these pathways in damaged tissue to assess their influence on regeneration.