PKD1 and cyst: The majority of ADPKD cases are due to mutations in either of two transmembrane proteins, polycystin-1 (Pkd1) and polycystin-2 (Pkd2), that form a heterotetrameric complex in the primary ciliary membranes [1] It is widely believed that perturbing this ciliary complex, either by loss-of-function mutations or disrupting cilia structure triggers the cellular phenotype that leads to cyst formation [2–4] Although the precise mechanism by which the polycystin complex preserves tubule architecture remains obscure, some aspects of pro-cystic signaling have been established.