Fig. 1. Expression of ISL1 in developing mouse retina. (A-F) The expression of ISL1 (red) is largely co-localized with that of BRN3B (green) in both migrating RGCs in the NBL and post-migrated RGCs in the GCL (arrows). Open and filled arrowheads indicate the occasional RGCs expressing BRN3B or ISL1 alone, respectively. (G-L) Most of ISL1+ cells (green) are not co-labeled with S- and M-phase markers (red), anti-BrdU (G-I) and anti-pH3 (J-L). (M-R) Expression of Isl1 is regulated by Math5 but not by Brn3b. (M,N,P,Q) Reduced expression of ISL1 (red) and BRN3B (green) in E13.5 Math5-null retinas. (O,R) The comparable Isl1 expression in wild-type (O) and Brn3b-null (R) retinas by in situ hybridization at E14.5. Insets show selected regions at higher magnification. R, retina; L, lens; NBL, neuroblast layer; GCL, ganglion cell layer. Scale bars: 100 µm.