NPHP2 in ciliary function, renal fibrosis and cyst formation

这项建议集中在肾单位(NPHP)基因，Nphp2，在肾纤维化和囊性形成中的细胞自主和非自主功能。NPHP是一种以间质纤维化和包囊为特征的隐性肾纤毛病变。尽管NPHP在儿童和年轻人的终末期肾脏疾病中占了相当大的比例，但目前还没有针对这种疾病的靶向治疗方法，其潜在的分子病因，特别是间质纤维化的分子病因尚不清楚，尽管NPHP蛋白已被放入不同的生化模块中。缺乏知识阻碍了为这种疾病开发有针对性的治疗的努力。以往的工作表明，Nphp2小鼠全身基因敲除模型在新生期表现为肾脏纤维化和包囊。通过建立和分析上皮和互补基质特异性Nphp2基因敲除小鼠模型，我们发现有缺陷的上皮细胞是间质纤维化和上皮性囊肿形成的驱动因素。此外，在上皮特异性Nphp2突变体中，肌成纤维细胞的激活发生在疾病进展的早期，并先于可检测到的囊泡形成。此外，纤毛基因的取消部分抑制了Nphp2突变体的表型，表明纤毛在Nphp2功能中起着重要作用。该项目的中心假设是，Nphp2抑制了肾上皮细胞中纤毛依赖的促纤维化和亲囊变途径，细胞自主和非自主反应都有助于疾病的进展。提出了两个具体的目标来检验这一假说。目的1以肾上皮细胞为研究对象。从体内表型特征、转录组图谱到途径分析的组合方法，以确定在Nphp2突变的上皮细胞中被破坏的关键途径。目的2主要研究上皮-间质间的串扰，并将确定间质细胞对NPHP2缺陷上皮细胞的反应，以及间质细胞是否改变了Nphp2突变体的表型。该项目的完成将提供对NPHP和纤毛介导的信号在不同生理和疾病状态下的分子和细胞病因学的重要见解。

This proposal focuses on both cell autonomous and non-autonomous function of the nephronophthisis (NPHP) gene, Nphp2, in renal fibrosis and cyst formation. NPHP is a recessive renal ciliopathy characterize by interstitial fibrosis and cysts. Although NPHP accounts for a significant portion of end stage renal disease in children and young adults, currently no targeted therapy is available for this disease and the underlying molecular etiology, particular for interstitial fibrosis, is not well understood, even though NPHP proteins have been put into different modules biochemically. The lack of knowledge hampers the effort to develop targeted therapy for this disease. Previous work showed that mouse whole-body knockout model of Nphp2 displays renal fibrosis and cysts at the neonatal stage. By generating and analyzing epithelial and complementary stromal specific knockout mouse models of Nphp2, we pinpointed defective epithelial cells as the driver for both interstitial fibrosis and epithelial cyst formation. In addition, myofibroblast activation occurred early during disease progression and preceded detectable cyst formation in the epithelial specific Nphp2 mutants. Moreover, abrogation of cilia genetically partially suppresses the phenotype of Nphp2 mutants, suggesting that cilia play a significant role in Nphp2 function. The central hypothesis of this project is that Nphp2 inhibits a cilia-dependent profibrotic and pro-cystic pathway in renal epithelial cells and that both cell autonomous and non-autonomous responses contribute to disease progression. Two specific aims were proposed to test this hypothesis. Aim 1 focuses on renal epithelial cells. A combination of approaches, from in vivo phenotype characterization, transcriptome profiling to pathway analysis to identify key pathways that are disrupted in Nphp2 mutant epithelial cells. Aim 2 focuses on epithelial-interstitial crosstalk and will determine how stromal cells respond to epithelial cells with defective NPHP2 and whether stromal cells modify phenotypes of Nphp2 mutants. Completion of this project will provide critical insight into the molecular and cellular etiology of NPHP and cilia-mediated signaling under diverse physiological and disease states.