Forming and Patterning the Vertebrate Inner Ear

描述（由申请人提供）：内耳的早期发育分为三个阶段：耳穴的形成，内耳最早的雏形；耳基体的形态发生，形成耳窝（杯）和耳囊肿；耳囊肿的中轴形成和局部模式。每个阶段的特点是不同组织之间的诱导相互作用。虽然有几个信号系统参与了这些阶段的控制，但成纤维细胞生长因子（FGF）信号显然起着关键作用，也是本研究的重点。该项目结合了两位研究者广泛的技术和科学专长，并使用两种动物模型来研究早期内耳发育的细胞、分子和遗传控制。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具体目标的实验。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这三个我们在上一个项目期间发现的影响卵细胞基因位形成的关键因素是如何定位于早期鸡胚胎的头侧近轴中胚层的。这将使我们能够确定内耳的雏形是如何在发育中的胚胎的头部中定位的。其次，我们将确定Fgf4和Fgf8在内耳雏形形成中的作用。先前项目期间的表达研究、实验胚胎学和遗传分析强烈地暗示了这两个因素在内耳发育中的作用。第三，我们将确定和比较Fgf16和Fgf3在小鼠和鸡内耳基本模式中的作用。先前项目期间对Fgf3/Fgf10突变体胚胎的表达研究和分析得出的假设是，这两个因素在发育中的内耳耳轴的形成和/或细胞类型的指定中起着至关重要的作用。利用我们在研究中采用的两种动物模型系统的独特优势，这一假设将得到严格的检验。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fgf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见解，这些机制是人类听觉系统严重先天缺陷形成的基础。

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.