CDH18 and ventricular septal defect: The only upregulated gene in Δ3.8/hIC1 endothelial cells compared to wild-type was Cadherin 18 (Cdh18) (Figure 6E), which was also upregulated in Δ3.8/+ samples compared to wild-type (Figure 6—figure supplement 4C) and clinically reported to be mutated in congenital heart defects (CHDs) including VSD (Chen et al., 2018; Soemedi et al., 2012).