In patients with polycystic liver diseases (autosomal-recessive polycystic kidney disease and autosomal-dominant polycystic kidney disease) TRPV4 is overexpressed in cholangiocytes, a finding that is reproduced in polycystic kidney rats, a model for autosomal-recessive polycystic kidney disease (Gradilone et al., 2010). The gene discussed is TRPV4; the disease is autosomal recessive polycystic kidney disease.