(A) Representative images of Nos3+/+ and Nos3S1176A/S1176A retinas collected at P7, stained with isolectin B4 (IB4). (B, C) Quantification of vascular area (B) and outgrowth from the optic nerve (C) at P7 in Nos3+/+ and Nos3S1176A/S1176A pups. (D) Representative images of the vessel front from whole mount retinas collected at P7 stained with Isolectin-B4 (IB4, red, upper), ERG (yellow, upper), and CD34 (green, lower), to visualize vessel outgrowth and tip cells in Nos3+/+ and Nos3S1176A/S1176A retinal vasculature. Scale bar = 50 µm. (E–G) Filopodia length (E), tip cell number (F), branch points (G) in Nos3+/+ and Nos3S1176A/S1176A retinas at P7. Mean ± S.E.M. n = 3 (Nos3+/+) and 4 (Nos3S1176A/S1176A) mice, five to six images per mouse; t-test.