(A) Macroscopic view of the origin of great arteries of neonates. Heterozygotes showed a normal structure (left), but homozygous pups showed impaired separation of ascending aorta and pulmonary artery (PTA) and interrupted aortic arch between left common carotid artery (LtCCA) and brachiocephalic artery (BCA) (arrowhead). Bars 0.5 mm. (B) HE staining of heart sections of neonates. PTA and VSD (asterisk) are visible. Cardiac valves are hypercellular compared to control mice. Bars 400 μm. (C) Elastic staining of the aorta. The lamellar structure of the aorta did not reveal any differences between homozygous and control mice. The absence of cellular material below the elastic lamellae in the left panel is the result of the loss of the adventitia during sample preparation. Bars 20 μm. aAo, ascending aorta; dAo, descending aorta; DA, ductus arteriosus; LA, left atrium; LV, left ventricle; PA, pulmonary artery; RA, right atrium; RV, right ventricle.