Figure 4.

M-opsin deletion prevents dorsal M cone degeneration in Lrat^−/−Opn1sw^−/−Opn1mw^−/− mice. A: Retinal sections from 6-month–old and 12-month–old wild-type (WT), Lrat^−/−Opn1sw^−/−, Lrat^−/−Opn1sw^−/−Opn1mw^−/− [triple knockout (KO)], and Opn1sw^−/−Opn1mw^−/− mice were labeled with anti-mouse cone arrestin antibody (in green). White arrowheads indicate unhealthy dorsal cones from 6-month–old Lrat^−/−Opn1sw^−/− mice with swollen outer and inner segments; white arrows, cones from 12-month–old Lrat^−/−Opn1sw^−/− mice that had lost outer segments; red arrows, cones from 12-month–old Lrat^−/−Opn1sw^−/− mice with broken/fragmented structure. Representative retinal images from the dorsal regions of the indicated genotype are shown. Nuclei were stained with DAPI. B: Quantitative results of relative cone numbers at the ventral, central, and dorsal retina from the indicated genotype. Data were normalized to WT dorsal region. C: M-opsin deletion reduces proteasomal stress in dorsal M cones in Lrat^−/−Opn1sw^−/− mice. The reporter Ub^G76V-green fluorescent protein (GFP) signal from the dorsal retinas of P18 Lrat^−/−Opn1sw^−/−Ub^G76V-GFP mice, Lrat^−/−Opn1sw^−/−Opn1mw^−/−Ub^G76V-GFP, and Ub^G76V-GFP control mice were labeled with an anti-GFP antibody (in green). Cones were labeled with rhodamine-PNA (in red). Arrows indicate dorsal cones from Lrat^−/−Opn1sw^−/−Ub^G76V-GFP mice that displayed GFP signal. Data are expressed as means ± SEM (B). n = 4 to 7 for 6-month samples (B); n = 4 to 6 for each genotype for 12-month samples (B). ∗∗P < 0.01, ∗∗∗P < 0.001 versus all other three genotypes at both 6 and 12 months (one-way analysis of variance with Tukey post hoc analysis). Scale bars: 20 μm (A); 10 μm (C). CIS, cone inner segment; COS, cone outer segment; ONL, outer nuclear layer; OPL, outer plexiform layer.