In contrast, Chop mRNA levels (an ER stress gene induced by PERK pathway)22,53 were not affected between Atf6+/− Rho+/P23H and Atf6−/−Rho+/P23H mice, which is consistent with previous studies showing that Chop was not induced during retinal degeneration in P23H rhodopsin mice and that the loss of CHOP had no impact on retinal degeneration based on histology or ERG31,54. This evidence concerns the gene RHO and retinal degeneration.