PKD1 and cystic kidney disease: A low frequency of renal Pkd1 gene inactivation and only a few renal cysts and more frequent hepatic cysts is reported from the conditional deletion of Pkd1 in MMTV-Cre mice [25], whereas the broadly expressed tamoxifen-Cre inducible inactivation of the Pkd1 gene in mice resulted in massive cystic transformation of renal tissue [26].