JAG1 and hereditary elliptocytosis: In stark contrast, JAG1 protein levels are low in HE (Fig. 1 C, D, Supplementary Figs. 1 and 2A, B), but is the most abundant ligand in GFI1 + IAHC (Fig. 1E, F, Supplementary Figs. 1 and 2A, B).