In contrast to HNF-1α, the renal-specific inactivation of HNF-1β develops polycystic kidney disease, and renal cyst formation is accompanied with a drastic defect in the transcriptional activation of several polycystic kidney disease (PKD)-related genes, such as Umod, Pkhd1, Pkd2 and Tg737/Polaris[8]. This evidence concerns the gene IFT88 and polycystic kidney disease.