Age- and sex- divergent translatomic responses of the retinal pigmented epithelium

Abstract

Purpose : Aging is the main risk factor for age-related macular degeneration (AMD), of which retinal pigmented epithelium (RPE) atrophy is a hallmark thought to precede photoreceptor loss. Genome-wide and gene expression studies of AMD and control RPE demonstrate epigenomic/transcriptomic changes during AMD onset and progression. However, mechanisms by which molecular alterations of normal aging impair RPE function and contribute to AMD pathogenesis are unclear. Our aim is to define the cell-specific translatomic profile of the RPE in both sexes and with old age and how age-driven expression changes relate to RPE/retina function.

Methods : We used female and male Aldh1l1-cre/ERT2^+/wt; NuTRAP^flox/wt (Aldh1l1- NuTRAP) mice which express EGFP and mCherry tags for cell-specific isolation of nuclei and ribosomes after tamoxifen induction. Electroretinograms (ERGs) were recorded from dark-adapted mice at 6, 12, and 24 months old (mo). At 6-24 mo, eyes were harvested and processed for immunohistochemistry/confocal imaging of RPE-choroid flatmounts; RPE ribosome bound RNA isolation via TRAP; qPCR; and stranded RNAseq profiling.

Results : EGFP and mCherry specifically co-localized to the RPE in Aldh1l1- NuTRAP mice. TRAP-RNA-seq translatomic analysis revealed enrichment of RPE marker genes from published human and mouse RPE transcriptomes. TRAP-RPE translatomes show separation by age and sex. Two-way-ANOVA revealed 894 differentially expressed genes (DEGs) with age and 335 DEGs with sex main effects. While most age differences (58%) were common to male and female RPE, 19-23% were sex-specific. Age-related up-regulated genes in the RPE are indicative of inflammatory process activation while down-regulated genes suggest activation of stress, detoxification, and cell de-differentiation responses. RPE translatomic changes were concordant with RPE functional impairment, as shown by reduced c-wave amplitude and delayed ERG response in old mice.

Conclusions : The Aldh1l1-NuTRAP model is ideal for RPE translatome studies. We find differential age- and sex- associated gene expression with overrepresentation of pathways related to inflammation in the RPE. Concordant with impaired RPE function, the phenotypic changes in the aged translatome suggest the aged RPE becomes immunologically active, in both males and females, with sex-specific signatures.

This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.