FIGURE 3

MNU-mediated injury predominantly affects rods, UV-cones and the outer plexiform layer. Schematics of photoreceptor organization in a transversal section (A) and frontal flattened view (B), based on Raymond and Barthel (2004), Lagman et al. (2015), and Noel et al. (2021). INL, inner nuclear layer; rONL, rod outer nuclear layer; cONL, cone outer nuclear layer; OPL, outer plexiform layer; RPE, retinal pigmented epithelium; DC, double cones (red/green spectral sensitivity); LC, long single cones (blue spectral sensitivity); SC, short single cone (UV spectral sensitivity). (C) Ubiquitin-promoter driven loxP-EGFP-loxP-mCherry transgene is expressed in blue and UV cones. Top panel shows a schematic illustration and the bottom panel displays a section of uninjured retina with ubi:EGFP transgene expression (green) and DAPI (blue). (D) Transversal retinal section stained with 4C12 antibody to visualize cell bodies and inner segments of rods (green), Phalloidin to detect F-actin (red) and DAPI (blue). In uninjured retina, colocalization between 4C12 and Phalloidin (arrows) is detected at the level of inner segments. F-actin is also present in the photoreceptor processes in the outer plexiform layer (outlined with a dashed lines). At 5 dpMNU, F-actin in the outer plexiform layer is missing and rod cells bodies and their inner segments are disorganized. (E) Identification of Xap-2 antibody (red) as a marker of photoreceptor outer segments on section of ubi:EGFP transgenic retinas. A strong expression is detected distally to the oil droplet in the UV cones (purple asterisks) and blue cones (cyan asterisks). (F) Identification of Xap-1 antibody (red) as a marker of the cone outer segment on section of ubi:EGFP transgenic retinas. A dotty localization of Xap1 is enriched distally to the oil droplet in the UV cones (purple asterisks). Dots of Xap-1 labeling are also observed in the outer segments of other photoreceptors, but at much less concentrated level. N ≥ 3.