Figure 1.

A. Genotyping of mouse embryos. Targeted deletion of exon 2 of Bmpr1a occurs only in mice expressing Cre and the floxed Bmpr1a gene. SM22α-Cre;Bmpr1a^flox/+ (f/+) and ^flox/flox (f/f) represent mice heterozygous and homozygous for the floxed gene, respectively. Mice expressing either Cre or floxed Bmpr1a gene represent the WT group. Any mutant (f/f ^R26R) or WT (WT^R26R) mouse expressing Cre and the R26R gene, expresses β-galactosidase and can be used for LacZ staining. B. Cre activity in SM22α-Cre;R26R;Bmpr1a^flox/flox embryos: Whole-mount LacZ staining of SM22α-Cre;R26R;Bmpr1a^flox/+ embryos showing blue staining in the heart (a, asterisk) and dorsal aorta (a, arrowhead) at E9.25, and in smaller vessels as well as somatic myotomes (b, arrowheads) at E10.5. C. Phenotype of SM22α-Cre;R26R;Bmpr1a^flox/flox embryos: Compared to WT SM22α-Cre;R26R;Bmpr1a^flox/flox mutants (b vs. a) appear normal at E9.5 and relatively reduced in size (d vs. c) at E10.5, and at E11, areas of hemorrhage are noted in their heart (asterisk), abdomen (asterisk), as well as near the mouth (arrowhead) and brain (arrowhead) (f vs. e). D.Percentage of SM22α-Cre;R26R;Bmpr1a^flox/flox genotype. Numbers of genotyped mice at each age are depicted between ( ).