Proper control of R-loop homeostasis is required for maintenance of gene expression and neuronal function during aging

Age-related loss of cellular function and increased cell death are characteristic hallmarks of aging. While defects in gene expression and RNA metabolism have been linked with age-associated human neuropathies, it is not clear how the changes that occur during aging contribute to loss of gene expression homeostasis. R-loops are DNA-RNA hybrids that typically form co-transcriptionally via annealing of the nascent RNA to the template DNA strand, displacing the non-template DNA strand. Dysregulation of R-loop homeostasis has been associated with both transcriptional impairment and genome instability. Importantly, a growing body of evidence links R-loop accumulation with cellular dysfunction, increased cell death and chronic disease onset. Here, we characterized the R-loop landscape in aging Drosophila melanogaster photoreceptor neurons. Our data shows that transcribed genes in Drosophila photoreceptor neurons accumulate R-loops during aging. Further, our data reveals an association between age-related R-loop accumulation and decreased expression of long and highly expressed genes. Lastly, we show that photoreceptor-specific depletion of Top3{beta}, a DNA/RNA topoisomerase associated with R-loop resolution, leads to both downregulation of of long genes with neuronal function and decreased visual response in flies. Together, our studies present novel data showing increased levels of R-loop in aging photoreceptor neurons, highlighting the link between dysregulation of R-loop homeostasis, gene expression and visual function.