HE is derived from arterial endothelium (AE), which we defined by higher expression of arterial-specific genes (e.g., Efnb2, Nrp1, Dll4) relative to venous-specific genes (e.g., Ephb4, Nrp2, and Nr2f2) (Zhu et al. 2020). The gene discussed is DLL4; the disease is hereditary elliptocytosis.