Since others have reported increased Gli1 in cystic kidneys of ciliary mutants, Ift140 and Arl13B conditional knock-out mice14,23, and we have observed increased Gli1 in cystic kidneys of Nek8jck/jck, Thm1 and Pkd1 conditional knock-out mice (on mixed strain backgrounds)22, suggesting a general role for elevated Hh signaling in renal cystogenesis, we investigated the Hh pathway in human ADPKD. The gene discussed is TTC21B; the disease is autosomal dominant polycystic kidney disease.