XPNPEP3 and cystic kidney disease: The N protein post-transcriptionally promotes XPNPEP3 (X-prolyl aminopeptidase 3), mutations in XPNPEP3 have somehow been implicated in the development of “nephronophthisis-like ciliopathy,” a cystic kidney disease (O'Toole et al., 2010; Singh et al., 2017).