Msx2 is an immediate downstream effector of Pax3 in the development of the murine cardiac neural crest.

The neural crest plays a crucial part in cardiac development. Cells of the cardiac subpopulation of cranial neural crest migrate from the hindbrain into the outflow tract of the heart where they contribute to the septum that divides the pulmonary and aortic channels. In Splotch mutant mice, which lack a functional Pax3 gene, migration of cardiac neural crest is deficient and aorticopulmonary septation does not occur.