NKX2-5 and ventricular septal defect: Inherited mutations of the Nkx2-5 gene are a common genetic cause of CHD in humans as they can result in an assortment of cardiac malformations, such as right isomerism, atrioventricular (AV) block, ventricular septal defect (VSD), and atrial septal defect (ASD) (5–9).