YAP restricts renal inflammation and mitigates kidney damage in nephronothisis related kidney disease.

Nephronophthisis (NPH) is an orphan recessive kidney disease mostly caused by mutations in NPHP1 and 20 other genes encoding proteins that localize to primary cilia. To date the pathways linking altered primary cilia function to progressive kidney scarring in NPH remain poorly defined and therapeutic options allowing NPH patients to escape end-stage kidney disease are lacking. Distinct proteins mutated in NPH interact with components of the Hippo pathway, an important regulator of cell fate. YAP (Yes-associated protein) overactivation has been shown to induce renal scarring while YAP inhibition showed protective effect in kidney diseases unrelated to NPH. Yet, the therapeutic potential of YAP inhibition in NPH has not been formerly assessed. Here we studied the impact of both genetic and pharmacologic YAP inhibition on the NPH-like phenotype caused by a bi-allelic mutation of Lkb1, a ciliary kinase interacting with NPHP1. Contrary to non NPH renal disease, our results reveal an unexpected protective role of YAP in Lkb1 mutant kidneys. Indeed, YAP genetic disruption drastically increase kidney disease burden in Lkb1 deficient mice, while pharmacologic inhibition of YAP failed to improve their phenotype. Collectively these results suggest that YAP inhibition is not a valid therapeutic strategy in NPH and suggest that LKB1 and YAP are parallel negative regulators of a yet uncharacterized pathway detrimental for kidney health.