HNRNPA1 and ventricular septal defect: Histological analysis revealed normal anatomy in both wild-type littermate controls and Hnrnpa1+/ct heterozygotes, whereas all 3 Hnrnpa1ct/ct homozygotes displayed ventricular septal defect (VSD) and persistent truncus arteriosus (PTA), which was caused by complete failure of OFT septation (Figure 2B).