COL1A1 and Renal cyst: Real-time RT-PCR showed that mesenchymal-to-epithelial transition and fibrosis formation genes were significantly up-regulated in cystic kidney from homozygous Pkd1Col1a1(3.6)-cKO mice compare with control Pkd1flox/flox mice (Fig. 9A–9F), but no such alterations were observed in heterozygous Col1a1(3.6)-Cre;Pkd1flox/+ mice (Fig. 9A–9F).