FIGURE 1.

Smooth and cardiac muscle-specific deletion of the Klf4 gene was associated with significant postnatal death and growth retardation. A, a schematic representation of smooth and cardiac muscle-specific deletion of the Klf4 gene is shown. The numbers shown represent Klf4 exons. Triangles represent the loxP sites. X, breeding. B, the genotype of 191 offspring from the breeding between SM22α-CreKI⁺ (CreKI)/Klf4^loxP/wt mice and SM22α-CreKI⁻/Klf4^loxP/loxP mice was examined by PCR at the time of birth. C, Kaplan-Meier survival curves for SM22α-CreKI⁺/Klf4^loxP/loxP, SM22α-CreKI⁺/Klf4^loxP/wt, SM22α-CreKI⁻/Klf4^loxP/loxP, and SM22α-CreKI⁻/Klf4^loxP/wt mice are shown (n = 36 per each genotype). A log-rank test for trend yielded. *, p < 0.05. D and E, representative pictures of SM22α-CreKI⁺/Klf4^loxP/loxP and SM22α-CreKI⁻/Klf4^loxP/loxP mice at P1 (D) and P28 (E) are shown. F, changes in the body weight of SM22α-CreKI⁺/Klf4^loxP/loxP, SM22α-CreKI⁺/Klf4^loxP/wt, SM22α-CreKI⁻/Klf4^loxP/loxP, and SM22α-CreKI⁻/Klf4^loxP/wt mice after birth are shown (n = 20∼25 per each genotype). *, p < 0.05 compared with other genotypes. Docta represent the mean ± S.E.