REGULATION OF UROGENITAL DEVELOPMENT

描述（由申请方提供）：尽管人类先天性缺陷定位于输尿管及其与肾脏的连接处的发生率很高，但对胚胎发育过程中控制输尿管芽（UB）分割成肾集合系统和输尿管的信号传导途径仍知之甚少。我们的初步数据表明，一个独特的间充质细胞群来自近轴中胚层选择性地围绕远端UB和分泌的因素，如骨形态发生因子4所需的图案输尿管。具体而言，我们提出BMP 4通过激活受体酪氨酸激酶信号传导的拮抗剂来控制输尿管结构，该受体酪氨酸激酶信号传导已知诱导分支形态发生。此外，我们发现，骨形态发生蛋白5，另一个因素分泌的输尿管周围间充质，诱导UB上皮细胞终末分化。本建议的目的是测试这些假设描述的分子机制控制输尿管形态发生，使用既定的命运映射，组织切除，免疫组化，形态学和转基因技术。目的：1）确定来源于近轴中胚层的输尿管结缔组织细胞的分化命运，并分析缺乏这些细胞时输尿管的形态发生。目的2）研究膜相关受体酪氨酸激酶拮抗剂Sprouty 1在输尿管发育过程中的表达与BMP信号传导位点的关系。将在不存在BMP信号传导的情况下在发育中的小鼠中分析输尿管结构和Sprouty 1的细胞分布。目的3）在体外和体内分析不存在BMP 5信号和存在异位BMP信号的情况下的终末尿路上皮细胞分化。拟议的实验结果将提供急需的洞察信号通路介导输尿管形态发生，这是一个过程，在人类中容易出现异常。

DESCRIPTION (provided by applicant): The signaling pathways controlling Ureteric Bud (UB) segmentation into the renal collecting system and ureter during embryogenesis remain poorly understood despite the high incidence of human congenital defects localized to the ureter and its junction with the kidney. Our preliminary data suggest that a unique mesenchymal cell population derived from paraxial mesoderm selectively surrounds the distal UB and secretes factors such as Bone Morphogenetic Factor 4 that are required for patterning the ureter. Specifically, we propose that BMP4 controls ureter structure by activating an antagonist of receptor tyrosine kinase signaling which is known to induce branching morphogenesis. In addition, we show that Bone Morphogenetic Protein 5, another factor secreted by periureteral mesenchyme, induces UB epithelia to terminally differentiate. The aims of this proposal will test these hypotheses describing the molecular mechanisms controlling ureter morphogenesis using established fate mapping, tissue removal, immunohistochemical, morphological, and transgenic techniques. Aim 1) The differentiated fate of ureteral connective tissue cells derived from paraxial mesoderm will be determined and ureter morphogenesis in the absence of these cells analyzed. Aim 2) The expression of membrane-associated Sprouty 1, an active receptor tyrosine kinase antagonist, will be correlated with sites of BMP signaling in the developing ureter. Ureter structure and the cellular distribution of Sprouty 1 will be analyzed in the developing mouse in the absence of BMP signaling. Aim 3) Terminal urothelial cell differentiation will be analyzed in vitro and in vivo in the absence of BMP5 signaling and in the presence of ectopic BMP signaling. Results of proposed experiments will provide much needed insight into the signaling pathways mediating ureter morphogenesis, a process that is prone to abnormalities in humans.