The Role of FGF Receptors in Lens Development

描述：细胞分化，增殖和凋亡的调节是任何活的多细胞生物体的基本要求。成纤维细胞生长因子（FGF）家族，在小鼠和人类中，由编码22种不同配体和4种酪氨酸激酶受体（FGFR 1 -4）的基因组成。已显示FGF刺激诱导眼透镜细胞的存活、增殖和分化。过表达几种不同FGF配体的转基因小鼠经历透镜上皮的异位分化。此外，Fgfr基因的条件性缺失导致透镜异常，这取决于缺失哪种受体以及缺失发生在透镜发育的哪个阶段。在透镜基板阶段单独缺失Fgfr 2不会阻止透镜纤维分化，但确实会导致透镜细胞周期退出的轻微延迟并损害透镜细胞存活。相反，在Fgfr 3无效背景下，通过在透镜囊泡阶段同时缺失Fgfr 1和Fgfr 2，可以防止透镜纤维分化。因此，FGF和FGFR在透镜生物学中起着至关重要的基础作用，并且是透镜纤维分化所绝对需要的。本申请的目的是检查在FGFR刺激之后介导透镜中FGF诱导的反应的相关生化途径。待检验的假设是Fgfrs介导透镜纤维分化的主要途径是通过激活中间对接蛋白FRS 2 α。该假设将通过（1）直接修饰小鼠Fgfr 2基因座以产生设计为a）破坏与FRS 2 α的相互作用的突变，B）破坏与PLC γ的相互作用和c）产生具有来自TrkC的胞内结构域的嵌合受体（一种也诱导FRS 2 α激活的受体）并测试这些不同的突变型Fgfr 2基因在功能性Fgfr 1和Fgfr 3受体不存在的情况下是否能够支持纤维分化反应;（2）在FRS 2 α中产生条件突变并诱导该基因的晶状体特异性丧失;（3）测试TrkC在体内诱导透镜上皮细胞中纤维分化应答的能力。该应用与公共卫生相关，因为白内障仍然是世界范围内最常见的致盲原因，并且FGF/FGFR信号传导在透镜发育中起重要作用。FGF信号传导在许多疾病过程中也起着重要作用，包括癌症，但FGF如何引起其作用的分子细节尚未完全解决。

DESCRIPTION: The regulation of cell differentiation, proliferation and apoptosis is a fundamental requirement for any living multicellular organism. The fibroblast growth factor (FGF) family, in both mice and humans, consists of genes encoding 22 different ligands and four tyrosine kinase receptors (FGFR1-4). FGF stimulation has been shown to induce survival, proliferation and differentiation in cells of the ocular lens. Transgenic mice over-expressing several different FGF ligands undergo ectopic differentiation of the lens epithelium. Furthermore, conditional deletion of Fgfr genes leads to lens abnormalities depending on which receptor is deleted and what stage of lens development the deletion takes place. Deletion of Fgfr2 alone during the lens placode stage does not prevent lens fiber differentiation, but does cause a slight delay in lens cell cycle withdrawal and compromises lens cell survival. In contrast, on an Fgfr3 null background, lens fiber differentiation can be prevented by simultaneous deletion of Fgfr1 and Fgfr2 at the lens vesicle stage. Therefore, FGFs and FGFRs play a vital and fundamental role in lens biology and are absolutely required for lens fiber differentiation. The purpose of this application is to examine the relevant biochemical pathway, subsequent to Fgfr stimulation, that mediates FGF-induced responses in the lens. The hypothesis to be tested is that the major pathway by which Fgfrs mediate lens fiber differentiation is through the activation of the intermediate docking protein FRS2alpha. This hypothesis will be tested by (1) direct modification of the mouse Fgfr2 locus to create mutations designed to a) disrupt interaction with FRS2alpha, b) disrupt interaction with PLCgamma and c) create a chimeric receptor with an intracellular domain from TrkC (a receptor that also induces the activation of FRS2alpha) and testing to see if these different mutant Fgfr2 genes can or can not support a fiber differentiation response in the absence of functional Fgfr1 and Fgfr3 receptors; (2) making a conditional mutation in FRS2alpha and inducing lens-specific loss of this gene; (3) testing the ability of TrkC to induce a fiber differentiation response in lens epithelial cells in vivo. This application is relevant to public health because cataract remains the most frequent worldwide cause of blindness and FGF/FGFR signaling plays an essential role in lens development. FGF signaling also plays fundamental roles in many disease processes including cancer, but the molecular details of how FGFs elicit their effects are not fully resolved.