Null and heterozygous Zic3 mice display a variety of cardiac defects such as TGA, interrupted aortic arch (IAA), atrial septum defect (ASD) and ventricular septal defect (VSD) in combination with various other developmental anomalies, thus resulting in a phenocopy of the clinical spectrum of malfunctions found in humans with heterotaxy [25]. The gene discussed is ZIC3; the disease is atrial septal defect.