Pathogenesis of persistent truncus arteriosus and dextroposed aorta in the chick embryo after neural crest ablation.

To investigate the contribution of cranial neural crest cells to the developing cardiovascular system in the chick embryo, cauterization of various regions of cranial neural crest was performed. Five regions may be distinguished, each of which contributes mesenchyme to pharyngeal (branchial) arches 1 through 4 and 6. Ablation of arch 3, 4, and 6 regions resulted in a high incidence of persistent truncus arteriosus (PTA) associated with anomalies of the aortic arch. Dextroposed aorta (DPA) or anomalies of the inflow tract were found in all ablation groups. Although anomalies of the aortic arch arteries were induced in all ablation groups and were usually associated with intracardiac anomalies, those of the third and right fourth aortic arch were most frequent in the arch 4 and arch 4 + 6 groups. Anomalies of the sixth aortic arch were most frequent after extensive ablations that included the arch 6 region. We speculate that PTA is a direct result of the decreased population of mesenchymal cells derived from the arch 3 through 6 neural crest regions. DPA or anomalies of the inflow tract may be related to altered hemodynamics due to anomalies induced by neural crest ablation. Anomalies of the aortic arch arteries may be caused by either the direct or indirect process.