Figure 5. CFP-containing ganglion cells express NeuN immunoreactivity, a marker commonly used to identify retinal ganglion cells. A: Transverse section of peripheral retina shows cyan fluorescent protein (CFP) expression in numerous cell bodies in the ganglion cell layer (GCL). B: Neuronal nuclei (NeuN) immunoreactivity is localized in ganglion cell somata in the GCL (and weak immunoreactivity is in cell bodies in the inner nuclear layer; INL). C: A merged image of A and B shows colocalization of CFP expression and NeuN immunoreactivity in most cell bodies in the GCL. The scale bar for A–C is 45 μm. D: A higher magnification image shows CFP fluorescence in large ganglion cells (arrows) in the GCL. E: The same section as in D shows NeuN immunoreactivity in numerous ganglion cell somata in the GCL (arrows). The small, weakly NeuN-immunoreactive cells are displaced amacrine cells (stars). F: A merged image of D and E shows colocalization of CFP and NeuN immunoreactivity in ganglion cells (arrows) and a lack of colocalization of CFP and NeuN immunoreactivity in displaced amacrine cells (stars). The scale bar for D-F is 25 μm. G: CFP is localized to brightly and weakly fluorescent cell bodies of various sizes in the GCL. The image is from a retinal wholemount located 1.5 mm from the optic nerve head in midperipheral nasal retina. H: The same region as in G shows NeuN immunoreactivity in numerous cell somata in the GCL, including ganglion cells and displaced amacrine cells. I: The merged image of G and H shows colocalization of CFP and NeuN immunoreactivity in numerous ganglion cell somata in the GCL. The scale bar for G-I is 45 μm. In C and F inner plexiform layer is abbreviated IPL, and outer plexiform layer is abbreviated outer plexiform layer (OPL).