Outflow tract septation and skeletal development depend on the GAP domain of Plexin-D1. (A) Pictures of the cardiac outflow tract of E18.5 embryos. Ao, Aorta; PA, pulmonary artery; TA, truncus arteriosus. (Scale bar, 300 µm.) (B) Alcian blue/Alizarin red staining of E18.5 skeletons. Arrow points to splitting of vertebral bodies. (Scale bar, 1 mm.)