ROLE OF NOTCH AND KIDNEY DEVELOPMENT

描述（由申请人提供）：在上一个资助期进行的遗传分析定义了Notch信号在肾脏生物学中发挥重要作用的两个阶段。Notch的第一个基本功能是在肾单位分割期间。Notch 2信号阻断远端身份并促进近端小管（PT）和足细胞（POD）身份，无论是细胞自主还是在邻近细胞中诱导它们。这种活动只是短暂的，在S形体（SB）形成后变得不稳定。Notch信号的第二个重要功能是在成年期充当肾小管上皮细胞稳态的守门人;在它们不存在的情况下，囊肿和肾功能不全在相当大一部分远系繁殖动物中自发发展，其中一些囊肿含有继续分裂和发展乳头状腺瘤的细胞，被认为是乳头状肾细胞癌（PRCC）的前体。损伤增加囊肿和乳头状腺瘤形成的频率。虽然这些研究结果解释了为什么人类Notch 2信号减少会导致Alagille综合征（AGS），并表明在这些患者中提高Notch 1活性应该改善健康，但他们没有确定Notch信号是否/如何指导PT和POD命运的获得。我们将利用在前一个资助期准备的细胞谱系追踪工具来解决以下问题：在Notch 2激活时，SB中的细胞组织是否是成人肾单位中肾单位亚结构组织的基础，并绘制成人去分化肾PT从损伤中恢复的潜力。这些命运定位研究将使我们能够询问经历Notch活性的SB细胞是否注定成为PT、POD、两者都不是或两者都不是，以及去分化的成人肾上皮细胞是否是命运限制性的或寡分化的。这些结果将指导我们随后寻找能够增强POD和PT再生的基因。在目标2中，我们将询问这些细胞如何获得它们的命运。在目标3中，我们将确定Notch缺失对成人囊肿和腺瘤形成的机制贡献。在目标4中，我们将开发策略，以瞬时增强AGS和PRCC中的Notch 1活性，其转化目标是开发旨在补偿AGS中Notch信号减少的临床干预措施。公共卫生相关性：我们发现降低Notch活性的突变不会导致发育异常，但会导致以后生活中囊肿的形成，其中30%会发展成类似于人类乳头状肾癌的肾腺瘤。由于Notch减少疗法被认为是在成年人中，Notch信号传导在肾脏发育过程中发挥的作用及其在维持成人肾小管中的作用的完整机制阐明仍然具有重大的科学和临床意义。

DESCRIPTION (provided by applicant): Genetic analysis conducted during the previous funding period defined two stages where Notch signals play an important role in kidney biology. The first essential function of Notch is during nephron segmentation. Notch2 signals block distal identities and promote proximal tubule (PT) and podocyte (POD) identities either cell autonomously or inducing them in neighboring cells. This activity is required only transiently, becoming dispensable after S-shaped body (SB) formation. A second important function of Notch signals is to act as gatekeepers of renal tubular epithelial homeostasis during adulthood; in their absence, cysts and renal dysfunction develop spontaneously in a substantial fraction of outbred animals with some cysts containing cells that continue to divide and develop papillary adenomas, thought to be the precursor for papillary renal cell carcinoma (PRCC). Injury increases the frequency of cyst and papillary adenoma formation. While these findings explain why reduced Notch2 signaling in humans causes Alagille syndromes (AGS), and suggest that elevating Notch1 activity in such patients should improve health, they do not establish if/how Notch signals direct the acquisition of PT and POD fates. We will take advantage of cell lineage tracing tools prepared during the previous funding period to address the issue of whether the cellular organization in the SB, at the time of Notch2 activation, underlies the organization of nephron sub-structures in the adult nephron and map the potential of de-differentiated renal PT recovering from injury in the adult. These fate mapping studies will allow us to ask if SB cells experiencing Notch activity are fated to become PT, POD, neither, or both, and if de-differentiated adult renal epithelial cells are fate-restricted or oligopotential. The results will direct our subsequent search for genes capable of enhancing POD and PT regeneration in injured adults. In Aim 2, we will ask how these cells acquire their fates. In Aim 3, we will determine the mechanistic contribution of Notch loss to cyst and adenoma formation in adults. In Aim 4, we will develop strategies to transiently augment Notch1 activity in AGS and PRCC with the translational goal of developing clinical interventions aimed at compensating for Notch signal reduction reduction in AGS. PUBLIC HEALTH RELEVANCE: We find that mutations reducing Notch activity that do not result in developmental abnormalities nonetheless contribute to formation of cysts later in life, 30% of which will develop renal adenomas resembling human papillary renal carcinoma. Since Notch reduction therapy is being considered in adult humans, a full, mechanistic elucidation of the role Notch signaling plays during renal development and its role in maintenance of adult renal tubules continues to be of great scientific and clinical importance.