PKD2 and autosomal dominant polycystic kidney disease: PATJ protein was originally identified localized in the tight junctions of epithelial cells (Bhat et al., 1999; Céline et al., 2002; Yoko et al., 2002) and was a novel regulatory element of the polycystin-2 (PC2) channel and involved in autosomal dominant polycystic kidney disease (ADPKD) (Duning et al., 2010).