NC-specific Foxc1 mutants at E14.5 have normal outflow tract (OFT) development with ventricular septal defects. (a, c) Control heart sections show normal OFT and ventricular development at the E14.5 time point. (b) NC-Foxc1-KO section at the E14.5 time point that exhibits normal OFT development, displayed by a distinct aorticopulmonary septum. (d) NC-Foxc1 KO section at the E14.5 time point that exhibits VSD, displayed by an indistinct interventricular septum. E14.5 sections cut in the transverse plane. Ao, aorta; Pt, pulmonary trunk; VSD, ventricular septal defect; Scale bars, 150 μm in A–D