Fig. 2. Notch pathway mutations and arteriovenous malformations. (A) In a wild-type mouse embryo, India ink injected into the heart in order to visualize blood flow exits through the aortic arch arteries and enters the descending dorsal aorta. (B) In an embryo with an endothelial cell-specific deletion of the Notch1 gene, the injected ink leaks directly into the venous system via arteriovenous malformations. Images courtesy of Luke Krebs and Tom Gridley.