Pax3 is essential for normal cardiac neural crest morphogenesis but is not required during migration nor outflow tract septation

► Systemic loss of Pax3 results in pulmonary atresia and abnormal remodeling of aortic arch arteries. ► Wnt1-cre mediated Pax3 deletion in mouse embryos does not cause heart defects. ► Wnt1-cre mediated neural crest genetic ablation results in conotruncal heart defects. ► Pax3 functions in early neural crest progenitor specification and formation.