Fig. 3. Rescue of retinal defects in adult Brn3b-null mice by Brn3a knock-in in Brn3b locus. Top, middle and bottom panels are representative of wild-type (Brn3b^lacZ/+), Brn3b^lacZ/AP mutant and Brn3b^3a/lacZ mice, respectively. (A-C) Hematoxylin and Eosin staining of the retinal structure. (D-F) X-Gal staining of Brn3b-lacZ-positive RGCs. (G-I) SMI32 immunostaining of neurofilament. (J-L) Whole-mount optic nerves and tracks. (M-O) Hematoxylin and Eosin staining of optic nerve cross-sections cut at the broken lines in J-L. Arrowheads indicate optic nerves. RPE, retinal pigmented epithelium; OS, outer segment; ONL, outer nuclear layer; OPL, outer plexiform layer; INL, inner nuclear layer; IPL, inner plexiform layer; GCL, ganglion cell layer. Scale bars: 100 µm in A-I; 300 µm in J-O.