DLL4 and diabetic macular edema: Our discovery that Notch signaling acts to sustain VEGF-induced barrier relaxation in primary human retinal endothelial cells, when coupled with the elevated Notch ligands DLL4 and Jagged1 observed in patients with diabetic macular edema [15], suggests that therapeutics modulating Notch signaling could help suppress VEGF-mediated vascular leakage.