PKD2 and autosomal dominant polycystic kidney disease: Similarly, PC1R4218X (R/X) mutant34, which corresponds to an ADPKD patient-derived truncating mutant R4227X lacking the intact coiled-coil domain22, 27, did not interact with endogenous PC2 (Fig. 2a,b) and failed to cause PC2 to translocate to cilia (Fig. 2h,i).