in situ hybridization of Twist1, Hand1 and Hand2 at E10.5 reveal partially overlapping expression. Twist1 is expressed in the cardiac neural crest, endocardial-derived cushions of the AVC, and the overlying endothelium as well as pericardium. Hand1 expression is coexpressed with Twist1 in the cardiac neural crest, the myocardium of the left ventricle, myocardial cuff, and is coexpressed in the pericardium with Twist1 (and Hand2). Hand2 expression robustly marks the endocardium, cushions of the AVC (coexpressed with Twist1), cardiac neural crest (coexpressed with Twist1 and Hand1) and within the epicardium.