Growth Factor Signaling in Intestinal Development

描述(申请人提供)：上皮，如胃肠道的衬里，能够进行持续的自我更新，因为它们包含一群未分化的干细胞，具有很大的自我更新能力，也可以产生子细胞，能够分化为上皮层正常功能所需的所有成熟细胞类型。在正常的胃肠道发育过程中，调节这种层次化的上皮组织建立的信号的性质还没有被确定。成纤维细胞生长因子(FGFs)是一个至少由23个相关的间充质衍生多肽生长因子组成的家族，在各种组织的正常个体发育过程中调节一系列的形态发生和分化事件。我们最近发现，成纤维细胞生长因子受体基因FGFR-3仅在肠隐窝上皮下三分之二的未分化细胞中表达，并且在隐窝形态发生过程中表达最高。此外，对FGFR3-/-小鼠肠道发育的初步研究表明，FGFR-3调节乳鼠肠道中新生隐窝形成的速度和复制的隐窝传输细胞的数量。这一建议的中心假设是，在正常的肠道个体发育过程中，通过FGFR-3信号调节多潜能上皮干细胞的命运和/或增殖。目的1确定FGFR-3介导的信号是否通过对干细胞增殖和/或程序性细胞死亡的影响直接调节正常肠道发育过程中上皮干细胞数量的扩张。FGFR3受体基因定向突变的小鼠将被用来确定FGFR3介导的信号对克隆干细胞数量和不同发育时间点的细胞凋亡的影响。目的2研究FGFR3对隐窝形态发生的影响是否通过依赖β-连环蛋白/TCF-4的机制来实现。文献中的证据表明，HMG转录因子TCF-4和Lef-1是隐窝上皮细胞增殖和凋亡事件的重要下游调节介质。细胞培养和动物模型将被用来确定通过FGFR3的信号是否可以调节TCF-4的活性。目标3的目标是定义FGFR3在肠道发育过程中用来调节形态发生事件的中间信号级联。将使用生化和分子方法相结合的方法来研究肠上皮细胞系中可操作的FGFR3信号通路，特别是那些撞击TCF-4的细胞系。

DESCRIPTION (provided by applicant): Epithelia, such as those lining the gastrointestinal tract, are able to undergo continuous self-renewal because they contain a population of undifferentiated stem cells that have a large capacity for self renewal and can also give rise to daughter cells which are able to differentiate into all of the mature cell types needed for normal function of the epithelial layer. The nature of the signals that mediate the establishment of this hierarchical organization of the epithelium during normal gastrointestinal development has not yet been defined. Fibroblast growth factors (FGFs) are a family of at least 23 related mesenchymally derived peptide growth factors that modulate a wide array of morphogenic and differentiation events occurring during normal ontogeny of a variety of tissues. We have recently found that expression of one FGF receptor gene, FGFR- 3, is restricted to undifferentiated cells in the lower two-thirds of the intestinal crypt epithelium and is maximally expressed during crypt morphogenesis. Additionally, preliminary studies of intestinal development in FGFR3-/- mice, demonstrate that FGFR-3 regulates both the rate of nascent crypt formation and the number of replicating crypt transit cells in the suckling mouse intestine. The central hypothesis of this proposal is that signaling through FGFR-3 regulates the fate and/or proliferation of the multipotent epithelial stem cells during normal intestinal ontogeny. Aim 1 is to determine whether FGFR-3-mediated signaling directly regulates expansion of the epithelial stem cell population during normal intestinal development through effects on stem cell proliferation and/or programmed cell death. Mice with targeted mutations in the FGFR3 receptor gene will be used to determine the effects of FGFR3 mediated signaling on the number of clonogenic stem cells and on apoptosis at various developmental time points. Aim 2 will examine whether the effects of FGFR3 on crypt morphogenesis are mediated through a beta-catenin/TCF-4 dependent mechanism. Evidence in the literature suggests that the HMG transcription factors TCF-4 and Lef-1 are important downstream regulatory mediators of proliferative and apoptotic events in the crypt epithelium. Both cell culture and animal models will be used to determine whether signaling through FGFR3 can modulate TCF-4 activity. The goal of aim 3 is to define the intermediate signaling cascades that FGFR3 uses to regulate morphogenic events during intestinal development. The operant FGFR3 signaling pathways in intestinal epithelial cell lines, especially those impinging on TCF-4, will be investigated using a combination of biochemical and molecular approaches.