RECIPROCAL INDUCTIVE INTERACTIONS IN KIDNEY DEVELOPMENT

这个项目的总体目标是了解控制增长的机制， 肾脏发育过程中输尿管芽的形态发生和分化。虽然已经确定GDNF通过受体酪氨酸激酶Ret和辅助受体GFRalpha1传递信号，在这一过程中发挥着重要作用，但下游机制仍然很不清楚。我们假设GDNF调节一组靶基因的表达，这些靶基因反过来调节发育中的输尿管芽的不同功能，包括生长、分支形态发生、分化为特定类型的集合管细胞，以及诱导间充质干细胞发生肾脏的因子的产生。 在目标1中，我们建议确定GDNF诱导或抑制其在输尿管芽中表达的靶基因。我们的初步数据表明，筛查将是非常有效的，并将使我们能够识别在肾脏发育中具有重要和不可预见的作用的各种基因。在目标2中，我们建议进行几个改进的筛选，以研究GDNF通过不同的Ret受体亚型和不同的细胞内信号通路调节其靶基因表达的机制。在目标3中，我们提出了一系列在小鼠模型上的功能研究，以探讨 肾发育中几个新的GDNF靶基因。最初要检测的靶基因将包括一个可能在输卵管芽分枝调控中发挥作用的趋化因子受体，一个可能参与肾发生诱导的分泌型细胞因子，以及一个可能介导次级靶基因调控的转录因子。建议的方法包括使用基因敲除和其他突变小鼠进行功能丧失研究，使用转基因小鼠进行功能获得研究，以及体外器官培养实验。输尿管芽形态发生的控制除了是发育生物学中的一个有趣的问题外，还具有重要的临床意义，因为肾脏发育不全、输尿管缺陷和肾发育不良是常见的出生缺陷，可以归因于肾脏发育的缺陷。 输尿管芽。

The overall goal of this project is to understand the mechanisms that control the growth, morphogenesis and differentiation of the ureteric bud during kidney development. While it is established that GDNF, signaling through the receptor tyrosine kinase Ret and the co-receptor GFRalpha1, plays an essential role in this process, the downstream mechanisms remain largely obscure. We hypothesize that GDNF regulates the expression of a set of target genes, which in turn mediate the different functions of the developing ureteric bud, including growth, branching morphogenesis, differentiation into specific collecting duct cell types, and production of factors that induce the mesenchymal stem cells to undergo nephrogenesis. In Aim 1 we propose to identify the target genes whose expression in the ureteric bud is induced or repressed by GDNF. Our preliminary data indicate that the screen will be highly effective and will allow us to identify a variety of genes with important and unforeseen roles in kidney development. In Aim 2 we propose to conduct several modified screens to investigate the mechanisms by which GDNF regulates the expression of its target genes, via different isoforms of the Ret receptor and different intracellular signaling pathways. In Aim 3 we propose a series of functional studies in mouse models to investigate the roles of several novel GDNF target genes in renal development. The initial target genes to be examined will include a chemokine receptor that may play a role in the regulation ofureteric bud branching, a secreted cytokine that may be involved in the induction of nephrogenesis, and a transcription factor that could mediate regulation of secondary target genes. The proposed methods include loss-of-function studies using knockout and other mutant mice, gain-of-function studies using transgenic mice, as well as in vitro organ culture experiments. In addition to being a fascinating problem in developmental biology, the control of ureteric bud morphogenesis has important clinical implications, as renal agenesis, ureteral defects and renal hypodysplasia are common birth defects that can of Len be attributed to defects in the development of the ureteric bud.