DDIT3 and retinitis pigmentosa: Moreover, we focused on ER stress as well as ROS in our light-induced retinal degeneration model because ER stress could mediate cell death via activation of the CHOP-dependent apoptotic pathway.25 In retinal diseases including retinitis pigmentosa, ER stress has been implicated in photoreceptor cell death.26 In our model, we found that SIRT3 KO retinas showed increased ER stress as well as increased ROS after the light exposure.