Characterization of SM22α-CreKI mice. A, Cellular expression of Cre-recombinase in SM22α-CreKI mice. X-Gal–stained organs and sections were prepared from 8-week-old SM22α-CreKI and Gt(Rosa)26Sor double heterozygous mice or wild-type littermates. X-Gal staining shows that Cre-recombinase is expressed in SMCs and cardiomyocytes in adult. B, Western blot analyses show GFP protein expressed in the aorta and the heart of 8-week-old SM22α-CreKI and Gtrosa26 double heterozygous or double homozygous mice and the control wild-type littermates. GFP protein is the positive control. Wt indicates wild-type; A, aorta; B, brain; H, heart; M, skeletal muscle. Bar = 100 µm.