REGULATION OF UROGENITAL DEVELOPMENT

描述(申请人提供)：胚胎发育过程中控制输尿管芽(UB)分割到肾脏收集系统和输尿管的信号通路仍然知之甚少，尽管人类先天性缺陷位于输尿管及其与肾脏的交界处的发生率很高。我们的初步数据表明，来自近轴中胚层的独特的间充质细胞群选择性地包围着输尿管远端，并分泌形成输尿管图案化所需的骨形态发生因子4等因子。具体地说，我们认为BMP4通过激活受体酪氨酸激酶信号的拮抗剂来控制输尿管结构，该信号拮抗剂可诱导分支形态发生。此外，我们还发现输尿管周围间充质细胞分泌的另一种因子--骨形态发生蛋白5可以诱导UB上皮细胞终末分化。这项提案的目的将检验这些假说，这些假说描述了控制输尿管形态发生的分子机制，使用既定的命运图谱、组织切除、免疫组织化学、形态和转基因技术。目的1)研究不同来源的输尿管中胚层结缔组织细胞的分化情况，并对其形态发生进行分析。目的2)膜相关酪氨酸激酶受体拮抗剂Sprouty 1的表达与BMP信号在输尿管发育过程中的部位有关。在没有BMP信号的情况下，将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)在无BMP5信号和存在异位BMP信号的情况下，对尿路上皮细胞终末分化进行体外和体内分析。拟议的实验结果将为调节输尿管形态发生的信号通路提供亟需的洞察力，这是一个容易在人类中出现异常的过程。

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.