PKD1 and polycystic kidney disease: ADPKD is caused primarily by mutations in PKD1 or PKD2, which encodes polycystin-1 (PC1) or polycystin-2 (PC2), respectively (polycystins or PCs collectively) (The European Polycystic Kidney Disease Consortium, 1994; Mochizuki et al., 1996).