PKD1 and cyst: Hematoxylin-eosin (H&E)-stained sections showed no cyst formation in liver tissues from all of three groups (Fig. 6B), in spite of 35% and 54% reduction in Pkd1 mRNA expression in heterozygous Col1a1(3.6)-Cre;Pkd1flox/+ and homozygous Col1a1(3.6)-Cre;Pkd1flox/flox mice, respectively (Fig. 1F).