Figure 4. Mice harboring a single intact allele of UbcM2 are not more susceptible to light-induced retinal degeneration. A: Inactivation of a single UbcM2 allele reduces expression of the enzyme by 58%. Equal amounts (10 μg) of retinal lysates derived from a UbcM2^+/− mouse and a wild-type (WT) littermate were subjected to denaturing and reducing sodium dodecyl sulfate PAGE (SDS–PAGE) followed by anti-UbcM2 western blotting. The migration of molecular weight markers is shown on the left. The asterisk denotes a nonspecific band serving as a loading control. The graph depicts the relative level of expression of UbcM2 in WT versus heterozygous littermates (n=3 of each genotype) as determined using a desktop scanner and Image J software. B: Representative hematoxylin and eosin (H&E) stained paraffin-embedded sections are shown from mice (UbcM2^+/− and WT littermates) 7 days after acute bright-light challenge. Control denotes animals that were maintained in dim light for the entire experiment. Abbreviations of retinal cell layers are as described in the legend for Figure 3. The magnification bar in panel A represents 50 μm. C: A Spider graph representing data compiled from the indicated number of animals for each experimental condition. The error bars represent the standard deviation. Outer nuclear layer (ONL) rows are plotted along the y-axis with inferior and superior distances in mm from the optic nerve head (ONH) depicted along the x-axis. There was no statistically significant difference in ONLs between WT and UbcM2^+/− control animals or between WT and UbcM2^+/− light-damaged animals.