Figure 2  Abnormal patterning of the PAAs in Alk5/Wnt1-Cre mutants. Left lateral view after intracardiac ink injections to visualize the developing PAAs at E11.0 (A,B), E12.0 (C, D) and E13.0 (E, F) in controls (A, C, E) and Alk5/Wnt1-Cre mutants (B, D, F). Arrow in A points to the regressing carotid duct. Asterisk in B depicts the corresponding structure in the mutant with no signs of regression. Asterisk in D illustrates the aberrant regression of the dorsal aorta between the 4th and 6th PAAs. PT, pulmonary trunk; Ao, Aorta; TA, truncus arteriosus.