Oxidative stress alters transcript localization of disease-associated genes in the retinal pigment epithelium

Nuclear retention is a mechanism whereby excess RNA transcripts are stored in the event that a cell needs to quickly respond to a stimulus; maintaining proper nuclear-to-cytoplasmic balance is important for cellular homeostasis and cell function. There are many mechanisms that are employed to determine whether to retain a transcript or export it to the cytoplasm, although the extent to which tissue or cell type, internal and external stressors, and disease pathogenesis affect this process is not yet clear. As the most biochemically active tissue in the body, the retina must mitigate endogenous and exogenous stressors to maintain cell health and tissue function. Oxidative stress, believed to contribute to the pathogenesis or progression of age-related macular degeneration (AMD) and inherited retinal dystrophies (IRDs), is produced both internally from biochemical processes as well as externally from environmental insult. Here, we evaluate the effect of oxidative stress on transcript localization in the retinal pigment epithelium (RPE), with specific focus on transcripts related to RPE function and disease.

We performed poly(A) RNA sequencing on nuclear and cytoplasmic fractions from human induced pluripotent stem cell-derived retinal pigment epithelium (iPSC-RPE) cells exposed to hydrogen peroxide (H₂O₂), as well as on untreated controls.

Under normal conditions, the number of mRNA transcripts retained in the nucleus exceeded that found in studies on other tissues. Further, the nuclear-to-cytoplasmic ratio of transcripts was altered following oxidative stress, as was the retention of genes associated with AMD and IRDs, as well as those that are important for RPE physiology.

These results provide a localization catalog of all expressed mRNA in iPSC-RPE under normal conditions and after exposure to H₂O₂, shedding light on the extent to which H₂O₂ alters transcript localization and potentially offering insight into one mechanism through which oxidative stress may contribute to the progression of visual disorders.