Fig. 3.

Disruption of ERK1/2 signaling results in cardiac outflow tract defects. Compared with controls (A–C), ERK2^fl/fl Wnt1:Cre embryos displayed variable penetrance of cardiac outflow defects, including double-outlet right ventricle (D), PTA (E), and VSDs (F). E16.5 cross-sections and dissected E17.5 embryos (atria dissected away) from ERK1^−/wt ERK2^fl/fl Wnt1:Cre (G–I) and ERK1^−/− ERK2^fl/fl Wnt1:Cre (J–L) embryos consistently exhibited PTA and VSDs (I and L). Whole-mount LacZ staining of Wnt1:Cre Rosa26^LacZ hearts reveals the distribution of neural crest derivatives in the embryonic conotruncus (M). Three-dimensional reconstructions (N) of cross-sections from E16.5 control embryos show a normal heart with 2 separate vessels, the aorta (red) and pulmonary artery (light blue), connected distally by the ductus arteriosus. Cross-sectional reconstructions of ERK1^−/− ERK2^fl/fl Wnt1:Cre hearts further illustrate PTA in these embryos (O). (ao = aorta, pa = pulmonary artery, rv = right ventricle, lv = left ventricle, la = left atrium, ra = right atrium, da = ductus arteriosus.)