NPHP2 in ciliary function, renal fibrosis and cyst formation

本研究主要关注肾纤维化（NPHP）基因Nphp2在肾纤维化和囊肿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囊肿为特征的隐性肾纤毛病。尽管NPHP在儿童和年轻人终末期肾脏疾病中占很大一部分，但目前尚无针对该疾病的靶向治疗方法，而且尽管NPHP蛋白已被生物化学地放入不同的模块中，但其潜在的分子病因，特别是间质纤维化的分子病因尚不清楚。知识的缺乏阻碍了开发针对这种疾病的靶向治疗方法的努力。先前的研究表明，Nphp2的小鼠全身敲除模型在新生儿期出现肾脏纤维化和囊肿。通过生成和分析上皮和互补基质特异性敲除Nphp2小鼠模型，我们确定了缺陷上皮细胞是间质纤维化和上皮囊肿形成的驱动因素。此外，在上皮特异性Nphp2突变体中，肌成纤维细胞激活在疾病进展早期发生，并先于可检测到的囊肿形成。此外，去除纤毛在遗传上部分抑制了Nphp2突变体的表型，这表明纤毛在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性的促纤维化和亲囊性通路，并且细胞自主和非自主反应都有助于疾病进展。为了验证这一假设，提出了两个具体目标。目的1聚焦于肾上皮细胞。结合多种方法，从体内表型表征，转录组分析到途径分析，以确定Nphp2突变上皮细胞中被破坏的关键途径。目的2侧重于上皮-间质串扰，并将确定基质细胞如何对NPHP2缺陷的上皮细胞做出反应，以及基质细胞是否会改变NPHP2突变体的表型。该项目的完成将为NPHP的分子和细胞病因学以及不同生理和疾病状态下纤毛介导的信号传导提供重要的见解。

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.