PKD2 and autosomal dominant polycystic kidney disease: Earlier work by Freedman et al. generated hiPSCs from patients with autosomal dominant polycystic kidney disease (ADPKD), which is caused by mutations in PKD1 gene, and found that hiPSCs and their differentiated cells showed a downregulation of polycystin 2, elucidating a novel mechanism in which polycystin 1 encoded by PKD1 gene regulates the expression of polycystin 2 [25].