Fig. 5. RGC and axon distribution in 3-week-old retinas. (A-C) Wild-type (A), Brn3b–/– (B) and Brn3b/Brn3c double mutant (C) retinas from the dorsal-nasal region. Retinas were labeled with anti-ß3-tubulin (RGCs and axons, green) and propidium iodide (nuclei, red). The number of axons in the Brn3b–/– retina (B) was greatly reduced when compared with that of the wild type (A). The number of axons deceased only slightly in the double-mutant retina (C). The thick branching green-labeled structures are blood vessels and capillaries nonspecifically labeled. (D-F) Enlarged views of wild-type (D), Brn3b–/– (E) and Brn3b/Brn3c double-mutant (F) retinas from the ventral-temporal region. Optic disks are located at the bottom out of frame. Retinas were labeled with anti-ß3-tubulin (RGCs and axons, green), ChAT (displaced amacrine cells, blue) and propidium iodide (nuclei, red). The number of axons was greatly reduced in the Brn3b/Brn3c double mutant retina (F) when compared with a Brn3b–/– retina (E). The thick branching green-labeled structures (arrows) are blood vessels and capillaries that were nonspecifically labeled with anti-mouse IgG secondary antibody. Note that excess capillaries were embedded in the RGC layer. Some large nuclei are surrounded by ChAT-positive signals in F. It is possible that these signals resulted from the processes of the overproduced amacrine cells. (G-I) The same images as D-F with the green and blue channels removed. The smaller condensed nuclei (blue arrows) correspond to ChAT-positive amacrine cells, while the large diffuse nuclei (green arrows) correspond to RGCs. (J-L) Low-magnification views of cross sections collected from wild-type (J), Brn3b–/– (K) and Brn3b/Brn3c double mutant (L) retinas. Sections were labeled as in D-F. Note the optic fiber layer in green at the bottom of the Brn3b–/– retina (K) is much thinner than that of the wild-type retina (J), and the optic fiber in the double mutant retina (L) is barely detectable. (M-O) Enlarged views of cross sections collected from wild-type (M), Brn3b–/– (N) and Brn3b/Brn3c double mutant (O) retinas. Labeling was the same as in D-F. RGCs are indicated by arrowheads.
