Autosomal dominant polycystic kidney disease is an important cause of end-stage renal disease, for which there is no proven therapy. Mutations in PKD1 (the gene encoding polycystin-1) are the principal cause of this disease. The disease begins in utero and is slowly progressive, but it is not known whether cystogenesis is an ongoing process during adult life. We now show that inactivation of Pkd1 in mice before postnatal day 13 results in severely cystic kidneys within 3 weeks, whereas inactivation at day 14 and later results in cysts only after 5 months. We found that cellular proliferation was not appreciably higher in cystic specimens than in age-matched controls, but the abrupt change in response to Pkd1 inactivation corresponded to a previously unrecognized brake point during renal growth and significant changes in gene expression. These findings suggest that the effects of Pkd1 inactivation are defined by a developmental switch that signals the end of the terminal renal maturation process. Our studies show that Pkd1 regulates tubular morphology in both developing and adult kidney, but the pathologic consequences of inactivation are defined by the organ's developmental status. These results have important implications for clinical understanding of the disease and therapeutic approaches.

Polycystin-1 (PC1) has an essential function in renal tubular morphogenesis and disruption of its function causes cystogenesis in human autosomal dominant polycystic kidney disease. We have previously shown that recombinant human PC1 is cis -autoproteolytically cleaved at the G protein-coupled receptor proteolytic site domain. To investigate the role of cleavage in vivo , we generated by gene targeting a Pkd1 knockin mouse ( Pkd1 V/V ) that expresses noncleavable PC1. The Pkd1 V/V mice show a hypomorphic phenotype, characterized by a delayed onset and distal nephron segment involvement of cystogenesis at postnatal maturation stage. We show that PC1 is ubiquitously and incompletely cleaved in wild-type mice, so that uncleaved and cleaved PC1 molecules coexist. Our study establishes a critical but restricted role of cleavage for PC1 function and suggests a differential function of the two types of PC1 molecules in vivo .

BackgroundThe major gene mutated in autosomal dominant polycystic kidney disease was first identified over 20 years ago, yet its function remains poorly understood. We have used a systems-based approach to examine the effects of acquired loss of Pkd1 in adult mouse kidney as it transitions from normal to cystic state.MethodsWe performed transcriptional profiling of a large set of male and female kidneys, along with metabolomics and lipidomics analyses of a subset of male kidneys. We also assessed the effects of a modest diet change on cyst progression in young cystic mice. Fatty acid oxidation and glycolytic rates were measured in five control and mutant pairs of epithelial cells.ResultsWe find that females have a significantly less severe kidney phenotype and correlate this protection with differences in lipid metabolism. We show that sex is a major determinant of the transcriptional profile of mouse kidneys and that some of this difference is due to genes involved in lipid metabolism. Pkd1 mutant mice have transcriptional profiles consistent with changes in lipid metabolism and distinct metabolite and complex lipid profiles in kidneys. We also show that cells lacking Pkd1 have an intrinsic fatty acid oxidation defect and that manipulation of lipid content of mouse chow modifies cystic disease.InterpretationOur results suggest PKD could be a disease of altered cellular metabolism.