Fig. 4. Loss of RGCs in adult Isl1-null retina. (A-G) Immunostaining of whole-mount retina with anti-BRN3A (A,B), BRN3B (C,D) and SMI32 (F,G) antibodies reveals the reduction of RGCs in Isl1-null retina. (E) Quantification of BRN3A+ and BRN3B+ cells in the central retinal region of the whole mounts (n=4 for each genotype) reveals a loss of 66% RGCs in Isl1-null retina. (H,I) Ventral views of brain show the thinner optic nerves (arrows) in Isl1 nulls. (J) Quantification of optic nerve size by measuring the cross area of H&E stained optic nerve transverse sections at the level indicated by arrows. Mean size of optic nerve in Isl1-null mice is reduced to 31% of that in wild type (n=6 pairs). Each histogram represents the mean+s.d. ^***P<0.001 (t-test). OC, optic chiasm; OT, optic tract. Scale bars: 50 µm in A; 100 µm in F; 1 mm in H.