NOTCH4 and cranioectodermal dysplasia: Although most genes in shared CeD-IBD loci reviewed here are known to have immune functions, NOTCH4, HES5, and SULT2B1 are known to be involved in the differentiation and maintenance of epithelial cells and hence in barrier function (as highlighted in the “Regulation of epithelial cell differentiation” cluster in Figure 1B, in pink).