The Role of FGF Receptors in Lens Development

描述：细胞分化、增殖和凋亡的调控是任何活着的多细胞生物体的基本要求。成纤维细胞生长因子家族在小鼠和人类中都由编码22种不同配体和四种酪氨酸激酶受体(FGFR1-4)的基因组成。研究表明，成纤维细胞生长因子可诱导晶状体细胞的存活、增殖和分化。过度表达几种不同的成纤维细胞生长因子配体的转基因小鼠经历了晶状体上皮的异位分化。此外，FGFR基因的有条件缺失会导致晶状体异常，这取决于缺失的受体以及缺失发生在晶状体发育的哪个阶段。在晶状体定位阶段单独删除FGFR2并不能阻止晶状体纤维的分化，但确实会导致晶状体细胞周期的轻微延迟，并影响晶状体细胞的存活。相反，在FGFR3缺失的背景下，可以通过在晶状体囊泡阶段同时缺失FGFR1和FGFR2来防止晶状体纤维分化。因此，FGFs和FGFRs在晶状体生物学中起着至关重要的基础作用，是晶状体纤维分化所必需的。这一应用的目的是检查FGFR刺激后的相关生化途径，该途径介导了晶状体中成纤维细胞生长因子诱导的反应。有待检验的假设是，FGFRs介导晶状体纤维分化的主要途径是通过激活中间对接蛋白FRS2pha。要验证这一假说，必须：(1)直接修改小鼠FGFR2基因座以产生突变，目的是a)破坏与FRS2pha的相互作用，b)中断与PLC的相互作用，c)创建一个具有TrkC细胞内结构域的嵌合受体(这种受体也会诱导FRS2pha的激活)，并进行测试，看看在缺乏功能性FGFR1和FGFR3受体的情况下，这些不同的突变FGFR2基因是否能支持纤维分化反应；(2)在FRS2pha上产生一个条件突变，并诱导该基因在晶状体上皮细胞中的特异性丢失；(3)测试TrkC在体内诱导晶状体上皮细胞进行纤维分化反应的能力。这一应用与公众健康相关，因为白内障仍然是全球最常见的致盲原因，而成纤维细胞生长因子/成纤维细胞生长因子受体信号在晶状体发育中起着至关重要的作用。成纤维细胞生长因子信号在包括癌症在内的许多疾病过程中也发挥着基本作用，但关于成纤维细胞生长因子如何发挥作用的分子细节还没有完全解决。

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.