Impact of phosphatidylinositol metabolism for ciliary biology and renal function

慢性肾脏病是一种常见疾病，其患病率在全球范围内不断增加。独立于其病因，肾功能受损的进展是基于纤维化重塑过程。然而，对潜在的分子因素和机制知之甚少。肾脏受累的单基因孟德尔遗传病提供了独特的潜力，以确定这些未知的因素，并提供进一步了解的分子机制，在这一发病机制。初级纤毛是存在于人体几乎每一个静止细胞表面的基于毛状细胞微管的细胞器，并且对多种基本细胞功能具有实质性的重要性。编码纤毛蛋白的基因突变导致广泛的复杂疾病，统称为“纤毛病”。表型谱的特征是早期肾间质纤维化和肾小管基底膜崩解。术语肾单位结核相关性纤毛病变（NPHP-RC）总结了一组罕见的常染色体隐性肾病，其占生命前三十年内遗传性终末期肾病的大多数。通过对一个患有NPHP-RC的受影响个体的全外显子组测序，我们鉴定了导致纤毛功能障碍的PIK 3C 2A中的纯合截短突变。该酶属于磷脂酰肌醇-3-激酶家族，其在细胞生理学中起关键作用，例如胞内和胞吐作用。PIK 3C 2A被检测到非常接近睫状体基底，其底物定位在睫状体轴丝内。然而，它的纤毛功能仍然未知。该项目计划研究PIK 3C 2A及其脂质产物的细胞和纤毛功能以及对CKD和纤毛病的病理生理学的重要性。因此，我们建立了纯合子、杂合子和野生型等位基因携带者以及不同分子原因的NPHP-RC受影响个体的原代人细胞培养物。这一资源使我们能够检查的作用，激酶的纤毛周运输过程和纤毛信号。将通过使用亚纯型Pik 3c 2a小鼠模型在体内研究酶及其产物的肾和肾外功能。为了检查磷酸肌醇途径的一般肾脏和睫状体功能，该项目将通过另一个小鼠模型（Inpp 5e）进行补充。这个项目将扩展纤毛生物学和肾脏重塑过程的理解，这可能与肾脏疾病有关。

Chronic kidney disease is a common disease and its prevalence is increasing worldwide. Independently of its etiology the progression of impaired kidney function is based on fibrotic remodeling processes. However, the underlying molecular factors and mechanisms are poorly understood. Monogenic, mendelian disorders with renal involvement offer the unique potential to identify these unknown factors and to provide further understanding of the molecular mechanisms involved in this pathogenesis. Primary cilia are hairlike cellular microtubule based organelles that exist on the surface of almost every quiescent cell of the human body and owe substantial importance for diverse essential cellular functions. Mutations in genes that encode for ciliary proteins lead to a broad complex of disorders, which have collectively been termed “ciliopathies”. The phenotypic spectrum is characterized by early renal interstitial fibrosis and tubular basement membrane disintegration. The term nephronophthisis-related ciliopathies (NPHP-RC) summarizes a group of rare autosomal-recessive kidney diseases which account for the majority of genetically caused end-stage renal disease during the first three decades of life. By whole exome sequencing of one affected individual with NPHP-RC we identified a homozygous truncating mutation in PIK3C2A leading to ciliary dysfunction. The enzyme belongs to the family of phosphatidylinositol - 3-kinases, which serve crucial roles in cell physiology, such as endo- and exocytosis. PIK3C2A was detected in close proximity to the ciliary base and its substrate localizes within the ciliary axoneme. However, its ciliary function remains unknown. This project plans to investigate the cellular und ciliary function of PIK3C2A and its lipid products as well as the importance for the pathophysiology of CKD and ciliopathies. Therefore, we established primary human cell cultures of the homozygous, the heterozygous and wildtype allele carrier as well as of affected individuals with NPHP-RC of different molecular causes. This resource enables us to examine the role of the kinase for periciliary transport processes and ciliary signaling. The renal and extra-renal function of the enzyme and its products will be investigated in vivo by using a hypomorphic Pik3c2a mouse model. In order to examine the general renal und ciliary function of the phosphoinositide pathway the project will be complemented by a further mouse model (Inpp5e). This project will extend the understanding of ciliary biology and renal remodeling processes which may have relevance to kidney dieases in general.