GSE184559
RNA-seq to determine the impact of miR-34 loss in the Drosophila brain with age
Aging is a risk factor for neurodegenerative disease, but precise mechanisms that influence this relationship are still under investigation. Work in Drosophila melanogaster identified the microRNA miR-34 as a modifier of aging and neurodegeneration in the brain. MiR-34 mutants present aspects of early aging, including reduced lifespan, neurodegeneration, and a buildup of the repressive histone mark H3K27me3. To better understand how miR-34 regulated pathways contribute to age-associated phenotypes in the brain, here we transcriptionally profiled the miR-34 mutant brain. This identified that genes associated with translation are dysregulated in the miR-34 mutant. The brains of these animals show increased translation activity, accumulation of protein aggregation markers, and altered autophagy activity. To determine if altered H3K27me3 was responsible for this proteostasis dysregulation, we studied the effects of increased H3K27me3 by mutating the histone demethylase Utx. Reduced Utx activity enhanced neurodegeneration and mimicked the protein accumulation seen in miR-34 mutant brains. However, unlike the miR-34 mutant, Utx mutant brains did not show similar altered autophagy or translation activity, suggesting that additional miR-34-targeted pathways are involved. Transcriptional analysis of predicted miR-34 targets identified Lst8, a subunit of Tor Complex 1 (TORC1), as a potential target. We confirmed that miR-34 regulates the 3' UTR of Lst8. Biological analysis of miR-34 mutant brains demonstrate that 4E-BP is hyperphosphorylated, consistent with increased Lst8 activity and changes in translation. Together, these results present novel understanding of brain aging and the role of the conserved miRNA miR-34 in impacting proteostasis in the brain with age. Overall design: Two independently run RNA-sequencing experiments are presented here. Set 1 compares the transcriptional profiles of Drosophila melanogaster brains with and without miR-34 at two timepoints (3d, 20d). Set 2 compares the transcriptional profile of the Drosophila melanogaster brain with age (3d, 20d, 50d). All conditions have 3 biological replicates.