Hedgehog gene regulatory networks in the mammalian kidney

项目概要/摘要 间充质肾单位祖细胞（MNP）产生哺乳动物肾脏中的所有肾单位小管。 这些细胞的过早消耗导致肾单位数量减少，增加高血压的风险 和各种肾脏疾病。为了干预MNP的过早耗尽，我们必须更好地了解 在发展过程中如何维持MNP人口。迄今为止， MNP在体内的维持知之甚少。我们的初步数据表明，刺猬信号 在MNP维护中起着重要作用。Hedgehog信号调节许多发育 流程. Hedgehog与Patched结合后，Smoothened（Smo）从Patched介导的免疫抑制中释放出来。 抑制，启动信号级联。为了测试刺猬信号在MNP中的潜在作用，我们 用Six 2Cre产生Smo突变肾脏，发现缺乏Smo的MNP过早耗尽， 在发育过程中，导致肾单位数量减少50%。我们的转录谱数据来自 Smo功能丧失和获得突变MNP显示Ptch 1表达与Smo表达之间的线性相关性。 剂量，这表明MNP确实对Hedgehog信号传导有反应。我们的数据显示Fox转录因子 是MNP中Hedgehog信号传导的下游靶点，Hedgehog信号传导的缺失导致MNP中Hedgehog信号传导的缺失。 Notch信号传导的激活，这是MNP的主要分化信号。基于我们的发现，我们假设 配体依赖的Hedgehog信号通过抑制Notch信号和激活Fox信号来维持MNP， 基因.我们建议（1）进行遗传分析，以确定是否刺猬信号增加自我更新 MNP和肾单位禀赋，（2）测试Notch的遗传衰减或药理学抑制 信号转导挽救了Smo突变MNP的过早耗尽，和（3）测试Fox转录因子的丢失是否 导致MNP的过早消耗和较低的肾单位数量。成功实现这些目标将 (1)为Hedgehog信号传导如何影响肾单位禀赋提供了新的见解，（2）确定直接靶点 MNP中Hedgehog信号传导下游的基因，（3）确定Fox转录因子是否起作用 在肾发生中的关键作用，和（4）改善体外肾类器官培养。

Project Summary/Abstract Mesenchymal nephron progenitor cells (MNPs) give rise to all nephron tubules in the mammalian kidney. Premature depletion of these cells leads to low nephron numbers, increasing the risk of high blood pressure and various renal diseases. In order to intervene in premature depletion of MNPs, we must better understand how the MNP population is maintained during development. To date, the processes required for the maintenance of MNPs in vivo are poorly understood. Our preliminary data suggest that Hedgehog signaling plays important roles in MNP maintenance. Hedgehog signaling regulates numerous developmental processes. Upon binding of Hedgehog to Patched, Smoothened (Smo) is relieved from Patched-mediated inhibition, initiating the signaling cascade. To test the potential role of Hedgehog signaling in MNPs, we generated Smo mutant kidneys with Six2Cre and found that MNPs lacking Smo were prematurely depleted during development, resulting in a 50% reduction in nephron number. Our transcriptional profiling data from Smo loss- and gain-of-function mutant MNPs show a linear correlation between Ptch1 expression and Smo dosage, suggesting that MNPs do respond to Hedgehog signaling. Our data show that Fox transcription factors are downstream targets of Hedgehog signaling in MNPs and that loss of Hedgehog signaling results in the activation of Notch signaling, a major differentiation signal for MNPs. Based on our findings, we hypothesize that ligand-dependent Hedgehog signaling maintains MNPs by repressing Notch signal and activating Fox genes. We propose to (1) perform genetic analyses to determine if Hedgehog signaling increases self-renewal of MNPs and nephron endowment, (2) test if genetic attenuation or pharmacological inhibition of Notch signaling rescues premature depletion of Smo mutant MNPs, and (3) test if loss of Fox transcription factors results in premature depletion of MNPs and lower nephron numbers. Successful completion of these aims will (1) provide novel insights into how Hedgehog signaling impacts nephron endowment, (2) identify direct target genes operating downstream of Hedgehog signaling in MNPs, (3) determine if Fox transcription factors play key roles in nephrogenesis, and (4) improve in vitro renal organoid cultures.