Urogenital System Development: The Acquisition of Coordinated Ureter Peristalsis

描述（由申请人提供）：围绕肾流出道（OT）的平滑肌层的协调收缩，包括肾盏、骨盆和输尿管，是将尿液排出肾脏所必需的。损害这种蠕动过程的先天性缺陷是常见的，也是儿童肾衰竭的主要原因。然而，控制介导尿路蠕动的细胞类型分化的信号通路仍然知之甚少。在之前的资助期内，我们发现骨形态发生蛋白信号在发育的早期阶段对OT平滑肌被的形成至关重要。在这个项目中，我们将研究在这个肌肉组织中协调收缩的分化细胞类型。我们最近发现OT平滑肌收缩的正常启动和协调依赖于超极化阳离子通道（HCN）活性。在目标1中，我们将使用我们最近开发的高分辨率视频显微镜和光学定位协议以及电子显微镜技术来确定表达HCN的OT细胞是否表现出触发平滑肌收缩所需的电生理和结构特性。此外，我们将通过分析HCN基因缺失小鼠的OT结构、平滑肌收缩和电活动来确定HCN通道活性是否对尿液从肾脏到膀胱的有效流动至关重要。我们还发现了酪氨酸激酶受体C-kit在控制OT收缩活性中的作用。在目标2中，我们将使用形态学和功能分析方法分析具有功能缺失突变C-Kit等位基因的小鼠的OT结构和平滑肌功能。Aim 3是基于我们的初步数据，表明携带构成型活性C-kit等位基因的小鼠会发生胎儿肾积水。我们将确定这种由C-kit功能获得引起的缺陷是由OT束的结构性闭塞引起的，还是如我们预测的那样，是协调蠕动的缺陷。总的来说，所提出的实验结果确定了触发协调的OT蠕动所需的细胞类型，将开辟一个新的研究领域，重点关注控制这些起搏器细胞分化的信号通路。最终，我们的研究将揭示改变输尿管蠕动的药物靶点，并可能揭示肾积水未被认识的原因。

DESCRIPTION (provided by applicant): Coordinated contractions of the smooth muscle coat surrounding the kidney outflow tract (OT), including the renal calyces, pelvis and ureter, are essential for draining urine out of the kidney. Congenital defects that impair this peristaltic process are common, and the leading cause of renal failure in children. However, the signaling pathways that control the differentiation of the cell types mediating urinary tract peristalsis remain poorly understood. In the previous funding period we showed that Bone Morphogenetic Protein signaling during the early stages of development is essential for the formation of the OT smooth muscle coat. In this project we will study the differentiated cell types that coordinate contraction in this musculature. We recently discovered that the normal initiation and coordination of OT smooth muscle contraction is dependent on Hyperpolarizing Cation Channel (HCN) activity. In Aim 1, we will determine if HCN expressing OT cells exhibit the electrophysiological and structural properties required for triggering smooth muscle contraction using our recently developed high resolution video-microscopic and optical mapping protocols and electron-microscopic techniques. Moreover, we will determine if HCN channel activity is essential for the efficient flow of urine from the kidney to the bladder by analyzing OT structure, smooth muscle contractile and electrical activity in mice with targeted HCN gene deletions. We have also uncovered a role for the tyrosine kinase receptor C-kit in controlling OT contractile activity. In Aim 2 we will analyze OT architecture and smooth muscle function in mice with loss-of-function mutant C-Kit alleles using morphological and functional assays. Aim 3 is based on our preliminary data demonstrating that mice harboring a constitutively active C-kit allele develop fetal hydronephrosis. We will determine if this defect due to C-kit gain-of-function is caused by a structural occlusion of the OT tract or as we predict, a defect in coordinated peristalsis. Collectively, the results of proposed experiments identifying the cell types required for triggering coordinated OT peristalsis will open up a new area of investigation focused on the signaling pathways controlling the differentiation of these pacemaker cells. Ultimately, our studies will reveal drug targets for the modification of ureter peristalsis and may reveal unappreciated causes of hydronephrosis.