NKX2-5 and familial atrioventricular septal defect: Overall, there was a marked increase in AVSD—69% with the Tie2+/Cre/Nkx2–5+/Cre:Lrp1f/f double Cre deletion vs. 13% with Tie2+/Cre: Lrp1f/f and 39% with Nkx2–5+/Cre:Lrp1f/f (Fig. 3).