Forming and Patterning the Vertebrate Inner Ear

描述(申请人提供)：内耳的早期发育经历了三个阶段：耳板的形成，内耳最早的雏形；耳板的形态发生，形成耳窝(杯)和耳囊；以及中轴的形成和耳囊的区域图案。每个阶段的特点是不同组织之间的诱导相互作用。尽管几个信号系统参与了这些阶段的调控，但成纤维细胞生长因子(成纤维细胞生长因子)信号显然扮演着关键角色，也是本提案的重点。该项目结合了两名研究人员广泛的技术和科学专长，并使用两个动物模型来研究早期内耳发育的细胞、分子和基因控制。为了研究内耳雏形的形成和模式，我们将进行旨在实现三个特定目标的实验。首先，利用组织重组实验和现代分子技术，我们将确定FGF19、Wnt8c和Fgf3是如何定位于早期鸡胚胎头侧中胚轴旁中胚层的。这将使我们能够确定内耳的雏形如何定位在发育中的胚胎的头部。其次，我们将确定Fgf4和Fgf8在内耳雏形形成中的作用。之前项目期间的表达研究、实验胚胎学和遗传分析强烈表明，这两个因素与内耳发育有关。第三，我们将测定和比较Fgf16和Fgf3在小鼠和雏鸡内耳发育过程中的作用。对前一个项目期间的Fgf3/Fgf10突变胚胎的表达研究和分析导致了这两个因素在发育中的内耳内耳轴的形成和/或细胞类型的指定中发挥重要作用的假说。这一假设将利用我们在研究中使用的两个动物模型系统的独特优势进行严格的测试。通过实现这三个目标，我们将获得关于内耳正常发育和调节其形成和模式的FGFs的重要新信息。此外，我们的研究将为这些发育过程出错的机制提供洞察力，这些机制是人类听觉系统严重出生缺陷形成的根本原因。

DESCRIPTION (provided by applicant): The early development of the inner ear occurs in three phases: formation of the otic placode, the earliest rudiment of the inner ear; morphogenesis of the otic placode, forming the otic pit (cup) and otocyst; and axis formation and regional patterning of the otocyst. Each phase is characterized by inductive interactions among different tissues. Although several signaling systems have been implicated in the control of these phases, Fibroblast Growth Factor (FGF) signaling clearly plays a critical role and is the focus of this proposal. This project combines the broad technical and scientific expertise of two investigators and uses two animal models to examine the cellular, molecular and genetic control of early inner ear development. To study the formation and patterning of the rudiments of the inner ear we will conduct experiments designed to achieve three specific aims. First, using tissue recombination experiments and modern molecular techniques, we will establish how fgf19, Wnt8c and fgf3, critical factors that we identified in the previous project period in formation of the otic placode, are localized in the cephalic paraxial mesoderm of the early chick embryo. This will allow us to determine how the rudiments of the inner ear are positioned within the head of the developing embryo. Second, we will determine the roles of Fgf4 and Fgf8 in formation of the rudiments of the inner ear. Expression studies, experimental embryology and genetic analyses from the previous project period strongly implicated these two factors in inner ear development. Third, we will determine and compare the roles of Fgf16 and Fgf3 in the patteming of the rudiments of the inner ear in mouse and chick. Expression studies and analyses of Fgf3/Fgf10 mutant embryos from the previous project period led to the hypothesis that these two factors play essential roles in formation of the otic axes and/or specification of cell types within the developing inner ear. This hypothesis will be rigorously tested taking advantage of the unique strengths of the two animal model systems that we employ in our studies. By achieving these three aims, we will gain important new information on the normal development of the inner ear and the FGFs that regulate its formation and patterning. Additionally, our studies will furnish insight into mechanisms by which these developmental processes go awry, underlying the formation of serious birth defects of the auditory system in humans.