Novel Role of Nephron Epithelialization in Nuclear Signaling

项目总结/摘要： 肾单位上皮化在核信号转导中的新作用 先天性肾脏和泌尿道异常（CAKUT）是导致需要肾移植的儿科终末期肾病的最常见原因。它们发生在近2%的新生儿中，占所有出生缺陷的近四分之一。然而，只有14%的病例有已知的遗传原因。许多CAKUT病例是由肾单位形成缺陷引起的，肾单位由肾脏正常功能所需的上皮小管组成。先前的研究表明，平面细胞极性（PCP）途径或外囊泡复合物的破坏导致肾小管畸形，表明这些成分是正确的肾小管形成所必需的。在我们以前的研究中，我们评估了如何通过PCP和外囊复合物独立地促进小管发生。我们研究了不同的模型，其中Daam 1，一种组装肌动蛋白丝作为Wnt/平面细胞极性途径的一部分的蛋白质，和Dnmbp/Tuba，调节胞外囊泡靶向，通过促进肾单位祖细胞之间的细胞-细胞接触的产生来促进小管形成。我们发现了一种新的机制，利用Wnt/PCP β蛋白Daam 1驱动肾单位祖细胞之间的细胞连接形成，通过聚合肌动蛋白来稳定粘附连接处的钙粘蛋白，从而产生小管。此外，我们的研究结果表明，外泌囊相关的组件Dnmbp促进靶向的连接组件，以启动这些细胞之间的肾单位祖细胞接触的形成。尽管取得了这些进展，但我们并不了解细胞间接触的形成如何影响发育中肾单位的小管上皮化和形态发生的发育过程。为了解决这个重要的问题，我们将在我们的重要发现的基础上，通过以下方式评估细胞连接形成如何影响肾小管的发育：1）确定Daam 1和Dnmbp之间的相互作用如何调节肾单位祖细胞之间的细胞-细胞接触形成，2）确定Daam 1在连接形成中的作用是否调节β-连环蛋白在肾发生过程中的连接与Wnt信号作用。总的来说，本申请中提出的实验将促进对细胞如何相互作用和通信以进行在多器官系统中具有相关性的小管形成的新理解。定量评价细胞的生物学机制参与肾脏的发展是一个新的研究领域，将有助于有价值的见解上皮化和形态发生机制的小管形成过程。

PROJECT SUMMARY/ABSTRACT: NOVEL ROLE OF NEPHRON EPITHELIALIZATION IN NUCLEAR SIGNALING Congenital anomalies of the kidney and urinary tract (CAKUT) are the most common cause of pediatric end- stage renal disease resulting in the need for kidney transplant. They occur in almost 2% of births, making up nearly one-fourth of all birth defects. However, only 14% of cases have a known genetic cause. Many CAKUT cases result from defects in the formation of nephrons, which are composed of epithelial tubules that are required for the proper function of the kidney. Prior studies indicate that disruption of either the planar cell polarity (PCP) pathway or exocyst vesicle complex result in malformation of the nephric tubules, indicating that these components are required for proper tubule formation. In our previous studies, we evaluated how tubulogenesis is facilitated through the PCP and exocyst complexes independently. We investigated distinct models by which Daam1, a formin protein that assembles actin filaments as part of the Wnt/planar cell polarity pathway, and Dnmbp/Tuba, which regulates exocytic vesicle targeting, facilitate tubulogenesis by promoting the generation of cell-cell contacts between nephron progenitor cells. We discovered a novel mechanism that utilizes the Wnt/PCP formin protein Daam1 to drive cell junction formation between nephron progenitor cells to generate tubules by polymerizing actin to stabilize cadherin at adherens junctions. Additionally, our results indicate that the exocyst-associated component Dnmbp facilitates the targeting of junctional components to initiate formation of these cell contacts between nephron progenitors. Despite this progress, we do not understand how the formation of cell-cell contacts influences the developmental processes of tubule epithelialization and morphogenesis in developing nephrons. To address this significant question, we will build upon on our important discoveries to evaluate how cell junction formation impacts the development of the nephric tubules by: 1) Identifying how the interaction between Daam1 and Dnmbp regulates cell-cell contact formation between nephron progenitors and 2) Determining whether Daam1’s role in junction formation regulates beta-catenin’s junctional versus Wnt signaling roles during nephrogenesis. Overall, the experiments proposed in this application will facilitate a new understanding of how cells interact and communicate to carry out tubulogenesis that has relevance in multiple organ systems. The quantitative evaluation of cell biological mechanisms involved in nephric development is a new area of study that will contribute valuable insights into epithelialization and morphogenesis mechanisms underlying tubulogenic processes.