Genetic dissection of ciliary ARL13B in kidney cystogenesis

该提案的目的是完善对与多囊肾病（PKD）相关的初级纤毛内信号传导机制的理解。肾囊肿会影响肾功能，并导致长期的严重健康并发症。PKD及其相关的健康并发症在美国每年造成70亿美元的经济负担，因此确定治疗的分子靶点是一个迫切的未满足的临床需求。纤毛是所有肾细胞上的细长突起，在细胞信号传导和囊肿形成中起关键作用，但其细节和潜在机制尚不清楚。常染色体显性遗传性多囊肾病（ADPKD）主要是由于纤毛相关多囊蛋白基因PKD 1和PKD 2突变所致。正常情况下，多囊蛋白在纤毛中起抑制促进囊肿的途径的作用。该途径的分子组分的鉴定，称为纤毛依赖性囊肿激活剂（CDCA），代表了对抗ADPKD的治疗策略的明确分子靶点。在研究CDCA通路和更普遍地理解纤毛信号传导方面的主要挑战是，该领域的工具太钝。小鼠模型通常会删除基因，导致纤毛和细胞蛋白质库的完全丧失，使得对纤毛特异性功能的任何解释都不可能。我们用睫状体GTCLARL 13 B（CDCA的一种建议介质）规避了这一挑战。我们通过工程改造表达纤毛排除的ARL 13 BV 358 A变体的小鼠来从纤毛中特异性地去除ARL 13 B，该变体保留了所有已知的生物化学活性。Arl 13 bV 358 A/V358 A小鼠是存活的且可生育的，但显示出囊性肾，这表明纤毛ARL 13 B的缺乏对肾囊肿形成特别关键。我们的目标是测试我们的核心假设，即纤毛ARL 13 B在调节肾脏囊肿发生中起关键作用。拟议的工作是重要的锻造基础知识的身份和时间的关键信号机制从内的主要纤毛，可能导致治疗干预PKD。

The objective of this proposal is to refine the understanding of the signaling mechanism(s) within the primary cilium in relation to polycystic kidney disease (PKD). Renal cysts interfere with kidney function and lead to major, long-term health complications. PKD and its related health complications result in a $7 billion per year economic burden in the United States so identifying molecular targets for treatment is a pressing unmet clinical need. Cilia, the slender protrusions on all renal cells, play key roles in cell signaling and cystogenesis but the details and underlying mechanism are ill-defined. Autosomal dominant polycystic kidney disease (ADPKD) is primarily due to mutations in the cilia-associated polycystin genes, PKD1 and PKD2. Normally, the polycystins function in cilia to suppress a pathway that promotes cysts. Identification of the molecular components of this pathway, termed the cilia-dependent cyst activator (CDCA), represents a clear molecular target for therapeutic strategies to counter ADPKD. The major challenge in working out the CDCA pathway, and in understanding ciliary signaling more generally, is that the tools in the field are too blunt. Mouse models typically delete genes, resulting in complete loss of both the ciliary and cellular pools of protein, making any interpretation of cilia-specific function impossible. We circumvented this challenge with the ciliary GTPase ARL13B, a proposed mediator of the CDCA. We removed ARL13B specifically from cilia by engineering a mouse expressing a cilia-excluded ARL13BV358A variant that retains all known biochemical activities. Arl13bV358A/V358A mice are viable and fertile yet display cystic kidneys indicating that it is the absence of ciliary ARL13B that is specifically critical to kidney cyst formation. Our goal in this proposal is to test our central hypothesis that ciliary ARL13B plays key roles in regulating kidney cystogenesis. The proposed work is important in forging fundamental knowledge of the identity and the timing of critical signaling mechanisms from within the primary cilium that could lead to therapeutic intervention for PKD.