Figure 3  Abnormal Aortic Sac in Alk5/Wnt1-Cre mutants. Alk5/Wnt1-Cre mutants (B, D) fail to form the typical T-shaped structure of the aortic sac seen in controls at E11.5. (A, C). A-B, frontal image of ink-injected embryos; C-D, frontal sections (H&E staining). Arrows in A and B point to the level of section shown in C and D (red arrows in C and D point to the aortic sac of the control and mutant, respectively).