Figure 5. RXRγ208-activated expression in PRs and all three HC subtypes. A–D: Fluorescence micrographs of embryonic day 14 (E14) retinas showing green fluorescent protein–positive (GFP+) cells that colocalize with markers for photoreceptors (PRs), axon-bearing horizontal cells (HCs; H1), and axon-less HCs (H2 and H3). E–F: Fluorescence micrographs of E18 retinas showing GFP+ cells colocalizing with rhodopsin but no colocalizing with the red or green opsin marker. G–H: Z-stacked confocal fluorescence micrographs of flatmounted retinas showing the presence of all three HC subtypes (H1, H2, H3) in the E14 and E18 embryos. Asterisk (*) denotes the axon terminal. I: Z-stacked confocal fluorescence micrographs of a flatmounted E18 retina showing the presence of PRs. J: Schematic model of the roles of RXRγ and Lim1 in photoreceptor and horizontal cell genesis. E = embryonic day; ONL = outer nuclear layer; INL = inner nuclear layer.