Figure 1.

Myocardial-specific inactivation of Smad4. A, Genomic DNA was extracted from yolk sacs of mouse embryos at E10.5 to determine their genotypes using PCR analysis with primers for Cre or for the unrecombined Smad4^loxp allele. B, Genomic DNA was extracted from hearts of the control (Smad4^loxp/loxp) and mutant (cTnt-Cre;Smad4^loxp/loxp) embryos examined in A. Semiquantitative PCR analysis was performed with primers for the unrecombined Smad4^loxp allele (top). Lanes 1 to 3 are control samples with 10%, 50%, and 100% of input DNA. Lane 4 is the mutant sample with 100% of input DNA. Tgfbr2 (an unrelated genomic DNA fragment) was used as a loading control (middle). Bottom, genomic DNA was subjected to PCR analysis using primers for the recombined Smad4^loxp allele. The PCR product could be detected in only the mutant sample and not in the control. C through D′, Sections of control (C and C′) and mutant (D and D′) mouse hearts at E10.5 were immunostained with an anti-Smad4 antibody (brown). Samples were counterstained with hematoxylin (blue). C′ and D′ correspond to the boxed regions of C and D, respectively. Cko indicates cTnt-Cre;Smad4^loxp/loxp; Ctrl, Smad4^loxp/loxp; Cu, cushion.