Characterizing Novel Regulators of Branching Morphogenesis within the Ureteric Bud Tip

 描述(申请人提供)：在许多器官系统中，包括肺和哺乳动物肾脏的集合管系统，分支形态发生过程支持树枝状上皮网络的形成。集合管起始于肾管形成输尿管芽(UB)。芽尖和随后扩张的输尿管上皮的分枝尖端的细胞对来自相邻间充质的诱导信号做出反应，促进和调节分枝形态发生，并在分枝尖端维持未确定的祖细胞群体。离开顶端进入茎区域的祖细胞分化为集合管网络中不同的细胞类型。我的目标是确定这些尖端细胞的独特分子特征，以获得对干细胞动力学和分支形态发生的重要见解。我利用了RNA测序数据，比较了发育中的小鼠肾脏尖端和柄结构域的基因表达。这些比较已经确定了一组强大的、富含TIP的基因，包括文献中所有已知的TIP调控基因。在目标1中，我将对发育中的小鼠肾脏和肺中的TIP丰富基因集进行详细的原位表达分析，以确定上皮形态发生的一般和肾脏特异性调节因子。在目标2中，我将建立输尿管尖端群体的细胞培养模型，通过遗传学方法系统地分析TIP富集型基因的功能。在目标3中，我将探索Adamts18(编码一种具有去整合素样酶的金属蛋白酶)的具体作用 和凝血酶反应蛋白1基序重复)。ADAMTS 18在肾脏和肺中均被鉴定为尖端富集型。我们已经分析了Adamts18个零突变，并显示出突变的一个子集显示肾增大并有双输尿管。因此，Adamts18通常被要求限制肾分支，并已成为分支形态发生的一种新的调节因子。

 DESCRIPTION (provided by applicant): A process of branching morphogenesis underpins the formation of arborized epithelial networks in many organ systems including the lung and collecting duct system of the mammalian kidney. The collecting duct initiates on formation of the ureteric bud (UB) from the nephric duct. Cells at the bud tip, and at subsequent branch tips of the expanding ureteric epithelium, respond to inductive signals from the adjacent mesenchyme that promote and regulate branching morphogenesis, and maintain an uncommitted progenitor population at the branch tip. Progenitors exiting the tip to populate stalk regions differentiate ito the regionally distinct cell types of the collecting duct network. I aim to ascertain the unique molecular features of these tip cells to gain vital insights into stem cell dynamics and branching morphogenesis. I have utilized RNA sequencing data comparing gene expression in tip and stalk domains expression of the developing mouse kidney. These comparisons have identified a strong, tip-enriched set of genes that include all known tip regulatory genes from the literature. In Aim 1, I will perform a detailed in situ expression analysis of the tip- enriched gene set in th developing mouse kidney and lung to identify general and kidney specific regulators of epithelial morphogenesis. In Aim 2, I will develop a cell culture model of the ureteric tip population to systematically analyze the function of tip-enriched genes through genetic approaches. In Aim 3, I will explore the specific actions of Adamts18 (encoding a metalloproteinase with disintegrin-like and thrombospondin type 1 motif repeats) in the branching process. Adamts18 was identified as tip-enriched in both the kidney and lung. We have analyzed Adamts18 null mutants and shown that a subset of mutants display enlarged kidneys with double ureters. Thus, Adamts18 is normally required to restrict kidney branching and has emerged as a novel regulator of branching morphogenesis.