In polycystic kidney rats in which mutations in the polycystic kidney and hepatic disease 1 gene cause cholangiocytes to undergo hyperproliferation and to form cysts, TRPV4 is overexpressed and mislocalized in the cholangiocytes, given that TRPV4 is present intracellularly rather than at the apical membrane and the cilia (Gradilone et al., 2010). The gene discussed is TRPV4; the disease is polycystic kidney disease.