PKD2 and autosomal dominant polycystic kidney disease: Autosomal dominant polycystic kidney disease (ADPKD), one of the most common genetic diseases in humans, is caused by mutations in either PKD1 or PKD2, two genes encoding polycystin-1 (PC1) and polycystin-2 (PC2, or TRPP2) protein, respectively (1, 2, 3, 4).