Role of Notch and Kidney Development

描述（由申请人提供）：发育异常占4岁以下儿童慢性肾衰竭的40%。在成人中，肾脏是疾病过程和药物毒性的主要侧枝靶器官。此外，心血管内稳态依赖于血压和电解质平衡的精确调节，没有良好的肾功能，这两者都无法维持；因此，确定肾脏发育和再生的分子调节因子对人类健康至关重要。许多信号（GDNF、LIF、FGF-2、tgf β、Wnt-4和Notch）控制着肾细胞的发育，而且毫不奇怪，许多信号被安排在反馈回路中，这样的信号整合维持了构成成人肾脏的多种肾细胞类型分化和发育所必需的信号平衡。充分阐明Notch信号在肾脏发育中的作用及其与其他信号通路的整合具有重要意义。支持Notch信号作用的遗传证据是，Notch配体Jagged I的部分缺失会影响人类的肾功能（alagille综合征），而Notch-2的亚形态突变会损害小鼠的肾小球发育。尽管有这些优秀的研究，Notch通路在肾脏发育所有阶段的作用尚不清楚，这是由于早期胚胎致命性和Notch受体的冗余性。所有Notch受体激活对蛋白酶的依赖性以及DAPT对早老素依赖性蛋白酶（7-分泌酶）的选择性使我们能够在器官培养系统中药理学上操纵Notch信号，从而避免致死性。我们的实验揭示了Notch信号在肾脏发育过程中比之前认识到的更早的时间运作的需求：我们发现7-分泌酶活性（因此Notch信号）对于近端上皮细胞命运（足细胞和近端小管）的规范是必不可少的；Notch在这一过程中的作用表明，Notch及其配体在肾纤维化模型中上调，可能在成人损伤后肾脏再生中起作用。本应用旨在确定几种肾损伤模型中发育和成人肾脏再生过程中Notch依赖过程和下游Notch靶点。

DESCRIPTION (provided by applicant): Developmental anomalies account for 40% of chronic renal failure in children under age 4. In adults, the kidney is a major collateral target organ of disease processes and drug toxicity. In addition, cardiovascular homeostasis depends on precise regulation of blood pressure and electrolyte balance, neither of which can be maintained without good renal function; therefore, identifying the molecular regulators of kidney development and regeneration are of critical importance to human health. Many signals (GDNF, LIF, FGF-2, TGFbeta, Wnt-4, and Notch) control nephron development and, not surprisingly, many are arranged in feedback loops, such that signal integration maintains the balance of signaling necessary for the differentiation and development of multiple renal cell types that compose the adult kidney. Fully elucidating the role of Notch signaling in kidney development and its integration with other signaling pathways is of great importance. The genetic evidence in support of a role for Notch signaling is that partial loss of the Notch ligand Jagged I affects kidney function in humans (Alagille-Syndrome) and hypomorphic mutations in Notch-2 impair glomemlar development in mice. Despite these excellent studies, the role of the Notch pathway during all stages of renal development is under-investigated due to early embryonic lethality and redundancy of Notch receptors. The dependence of all Notch receptor activation on proteases and the selectivity of DAPT for presenilin-dependent protease (7-secretase) permit us to pharmacologically manipulate Notch signaling in an organ culture system, circumventing lethality. Our experiments uncovered a requirement for Notch signaling operating at an earlier time during kidney development than was previously appreciated: we discovered that 7-secretase activity (and thus Notch signaling) is essential for specification of proximal epithelial cell fates (podocyte and proximal tubule); a role for Notch in this process suggests a possible role in kidney regeneration post injury in adults, where Notch and its ligands are up-regulated in a renal fibrosis model. This application Specific Aims to identify Notch-dependent processes and downstream Notch targets during development and during adult kidney regeneration in several renal injury models.