Sections through SrfaI/flox; Wnt1-CreTg/+ and control Srfflox/+; Wnt1-CreTg/+ hearts confirmed the macroscopically observed PDAs and also revealed one instance of ventricular septal defect (VSD) with persistent truncus arteriosus (PTA), a failure of the truncus arteriosus to fully septate into the aorta and pulmonary artery, out of ten mutant hearts examined (Figure 5D). This evidence concerns the gene WNT1 and ventricular septal defect.