Genetic Regulation of Inner, Middle and Outer Ear Development

项目摘要 哺乳动物的内耳、中耳和外耳具有不同的胚胎起源，但 听觉器官的每个组成部分必须在空间和时间上精确同步。理解 管理和协调这些结构的发展的机制在以下方面至关重要： 了解许多影响听力的出生缺陷的基础。我们已经确认了一个叉头 一种转录因子，Foxi 3，在胚胎头部的非常早期阶段表达。Foxi 3小鼠 我们实验室制造的突变体缺乏内耳、中耳和外耳的所有组成部分。我们的工作表明 耳朵诱导的第一步-耳基板的形成-在Foxi 3突变体中不发生。 此外，第一和第二鳃弓的间充质产生中耳小骨， 在Foxi 3突变体中，外耳开始形成，但很快就大量细胞死亡。而且我们 最近发现了患有Foxi 3变体的人类患者，这些患者在听力方面有各种缺陷 装置 据我们所知，Foxi 3是唯一一个导致胚胎发育完全失败的哺乳动物基因。 整个内耳，中耳和外耳当自身突变时。因此，我们非常感兴趣， 了解Foxi 3如何在细胞和分子水平上协调听觉器官的发育 程度.我们的数据表明，Foxi 3可能作为一个“先锋”转录因子-它的主要功能，除了 启动转录的目的是在表观遗传学上组织含有耳特异性基因的基因组位点， 有转录能力的国家。我们的前两个目标将确定Foxi 3在治疗中的功能和机制。 使用基因敲除小鼠、鸡胚操作和最先进的ES细胞的内耳发育 模型、深度测序和生物信息学分析。我们的最终目标是关注Foxi 3基因在 中耳和外耳的发育-在这里，我们将研究小鼠中失去Foxi 3的影响， 而且还能制造出小鼠突变体，重现我们在一些人类患者身上看到的遗传变异。

PROJECT SUMMARY The mammalian inner, middle and outer ears have different embryonic origins, yet the development of each component of the auditory apparatus must be precisely synchronized in space and time. Understanding the mechanisms that regulate and co-ordinate the development of these structures is of central importance in understanding the basis of the many birth defects that affect hearing. We have identified a Forkhead transcription factor, Foxi3, that is expressed at very early stages in the embryonic head. Foxi3 mouse mutants made in our lab lack all components of the inner, middle and external ears. Our work suggests that one of the first steps in ear induction– the formation of the otic placode – does not occur in Foxi3 mutants. Moreover, the mesenchyme of the first and second branchial arches that generate the middle ear ossicles and the external ear begins to form in Foxi3 mutants, but rapidly succumbs to massive cell death. Moreover, we have recently identified human patients with Foxi3 variants that have a variety of defects in their hearing apparatus To our knowledge, Foxi3 is the only mammalian gene that causes a complete developmental failure of the entire inner, middle and outer ears when mutated by itself. We are therefore extremely interested to understand how Foxi3 orchestrates development of the auditory apparatus at both the cellular and molecular levels. Our data suggests that Foxi3 may act as a “pioneer” transcription factor – its main function in addition to initiating transcription is to epigenetically organize genomic loci containing ear-specific genes in a transcriptionally competent state. Our first two aims will determine the function and mechanism of Foxi3 during development of the inner ear using knockout mice, chick embryo manipulations and state-of-the-art ES cell models, deep sequencing and bioinformatic analysis. Our final aim focuses on the function the Foxi3 gene in the development of the middle and external ear – here we will both study the effects of loss of Foxi3 in mice, but also create mouse mutants that recapitulate the genetic variants seen in some of our human patients.