Roles of transcription factors in kidney development

描述（由申请人提供）：在哺乳动物中，肾脏发育涉及到后肾间质（MM）的规范，输尿管芽（UB）的生长，以及它正确的分支形态发生，以产生输尿管和肾收集系统。众所周知，GDNF/Ret信号在小鼠的这些过程中起着核心作用。然而，控制MM特异性和影响UB及其分支形态发生的基因，以及Gdnf在MM中的表达调控机制尚不清楚。本研究的长期目标是阐明Eya1和Six1控制正常肾脏发育的机制。人类这些基因的缺陷会导致支气管-耳-肾（BOR）综合征，这是一种以支气管、耳部和肾脏异常为特征的先天性出生缺陷。为了了解BOR综合征肾缺陷的发育和分子基础，我们对BOR患者EYA1和SIX1基因的突变进行了功能分析，并通过基因靶向产生了EYA1和SIX1突变小鼠。我们的研究结果表明，Eya1指定MM，并且是MM中Gdnf表达的关键调节因子。我们发现Eya1作用于Six1的上游，但两个基因产物在肾脏发育过程中相互作用。此外，我们已经证明Six1通过介导Gdnf、Six2和Pax2在MM中的表达，是分支形态发生的关键调节因子。我们还证明，在BOR患者的EYA1或Six1基因中发现的突变影响了EYA1 -Six1相互作用或Six1- dna结合，从而为人类肾脏发育疾病的分子基础提供了新的见解。该应用将继续确定Eya1和Six1驱动正常肾脏发育的分子和发育机制。首先，我们将研究Eya1指定MM并驱动正常肾形成的机制。接下来，我们将探讨Eya1活性在肾脏发育中的调节作用。最后，我们将定义Six1启动分支形态发生的机制。这些研究将使我们对介导正常肾脏发育的Eya1-Six1的多层调控机制的理解得到显著改善。此外，这些结果将为了解BOR综合征肾缺陷的发育和分子发病机制提供重要的见解。公共卫生相关性：叙述：先天性肾脏和尿路疾病，包括肾脏发育不全、发育不良和尿路梗阻，是最常见的出生缺陷类型。这项资助申请旨在阐明这些先天性疾病的分子和发育发病机制，并解决一些关键问题，即一组转录因子何时以及如何介导正常输尿管和肾脏的发育。识别基因和蛋白质，了解它们在肾脏从一小群祖细胞发育成一个复杂器官过程中的作用和功能，可能最终导致预防或修复这类先天缺陷。

DESCRIPTION (provided by applicant): In mammals, kidney development involves the specification of the metanephric mesenchyme (MM), the outgrowth of the ureteric bud (UB), and it's correctly patterned branching morphogenesis to generate the ureter and the renal collecting system. It is known that GDNF/Ret signaling plays a central role in these processes in mice. However, the genes that control the specification of MM and pattern the UB and its branching morphogenesis, and the regulatory mechanism of Gdnf expression in the MM are still poorly understood. The long-term objective of this proposal is to elucidate the mechanisms by which Eya1 and Six1 control normal kidney development. Defects in these genes in humans cause Branchio-Oto-Renal (BOR) syndrome, a congenital birth defect characterized by combinations of branchial, otic and renal anomalies. To understand the developmental and molecular bases of renal defects that occur in BOR syndrome, we analyzed the mutations identified in the EYA1 and SIX1 genes from BOR patients functionally and generated Eya1 and Six1 mutant mice through gene targeting. Our results indicate that Eya1 specifies the MM and is a critical regulator for Gdnf expression in the MM. We found that Eya1 acts upstream of Six1 but both gene products interact during kidney development. Furthermore, we have shown that Six1 is a critical regulator for branching morphogenesis by mediating the expression of Gdnf, Six2 and Pax2 in the MM. We also demonstrated that the mutations identified in either the EYA1 or SIX1 gene from BOR patients affected either Eya1-Six1 interaction or Six1-DNA binding, thus providing new insights into the molecular basis of renal developmental diseases in humans. This application will continue to define the molecular and developmental mechanisms by which the Eya1 and Six1 drive normal kidney development. First, we will investigate the mechanisms by which Eya1 specifies the MM and drives normal nephrogenesis. Next, we will investigate the regulation of Eya1 activity in kidney development. Lastly, we will define the mechanism by which Six1 initiates branching morphogenesis. These studies should lead to significant improvements in our understanding of the multilayer control mechanisms by Eya1-Six1 that mediate development of a normal kidney. In addition, these results will provide important insights into the developmental and molecular pathogenesis of renal defects occurring in BOR syndrome. PUBLIC HEALTH RELEVANCE: Narratives: Congenital kidney and urinary tract disorders, including renal agenesis and hypodysplasia and urinary tract obstruction, are the most common types of birth defects. This grant application proposes to elucidate the molecular and developmental pathogenesis of these congenital diseases and address several key questions of when and how a set of transcription factors act to mediate development of a normal ureter and kidney. Identifying the genes and proteins and understanding their roles and functions in the development and growth of the kidney from a small group of progenitor cells to a complex organ may eventually lead to prevention or repair of such birth defects.