Hedgehog gene regulatory networks in the mammalian kidney

项目摘要/摘要 哺乳动物肾脏中的间充质肾单位祖细胞(MNPs)形成所有的肾小管。 这些细胞过早耗尽会导致肾单位数量减少，从而增加患高血压的风险。 以及各种肾脏疾病。为了干预MNPs的过早枯竭，我们必须更好地了解 在发展过程中如何维持MNP人口。到目前为止，需要的流程是 MNPs在体内的维持机制还知之甚少。我们的初步数据显示刺猬的信号 在MNP维护中发挥着重要作用。Hedgehog信号调节许多发育 流程。在Hedgehog与Patted结合后，Smoothened(Smo)从Patted-Mediated中解除 抑制，启动信号级联反应。为了测试Hedgehog信号在MNPs中的潜在作用，我们 产生了带有Six2Cre的Smo突变肾脏，并发现缺乏Smo的MNPs过早耗尽 在发育过程中，导致肾单位数量减少50%。我们的转录特征数据来自 SMO功能缺失和功能获得突变MNPs显示ptch1表达与SMO呈线性相关 剂量，这表明MNPs确实对Hedgehog信号有反应。我们的数据显示福克斯转录因子 是MNPs中Hedgehog信号的下游目标，并且Hedgehog信号的丢失导致 Notch信号的激活，这是MNPs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来维持MNPs 基因。我们建议(1)进行遗传分析以确定Hedgehog信号是否增加自我更新 (2)检测Notch的遗传衰退或药理抑制作用 信号挽救Smo突变MNPs的过早耗尽，以及(3)检测Fox转录因子是否丢失 导致MNPs过早耗尽，肾单位数量减少。这些目标的成功实现将 (1)对Hedgehog信号如何影响肾单位捐赠提供新的见解；(2)确定直接目标 MNPs中Hedgehog信号下游的基因，(3)决定Fox转录因子是否发挥作用 在肾脏发生中的关键作用，以及(4)改进体外肾脏器官培养。

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.