Early regulative ability of the neuroepithelium to form cardiac neural crest

► Removal of the cardiac neural crest after neural tube closure results in outflow tract septation defects and abnormal branchial arch arteries. ► Ablation of presumptive cardiac crest at earlier stages (i.e., stage 7), as the neural folds elevate, results in reformation of migrating cardiac neural crest, normal outflow tract septation and variably normal vessels. ► Dye labeling shows that the new cardiac neural crest derives from rhombomere 5 rostral to and the neuroepithelium ventral to the ablation. ► The stage of ablation dictates the competence of residual tissue to regulate and regenerate cardiac neural crest, as this capacity is lost by closed neural tube stage.