Sedentary Behavior Impacts on the Epigenome and Transcriptome: Lessons from Muscle Inactivation in Drosophila Larvae

The biological mechanisms linking sedentary lifestyles and metabolic derangements are incompletely understood. In this study, temporal muscle inactivation in Drosophila larvae carrying a temperature-sensitive mutation in the shibire (shi¹) gene was induced to mimic sedentary behavior during early life and study its transcriptional outcome. Our findings indicated a significant change in the epigenetic profile, as well as the genomic profile, of RNA Pol II binding in the inactive muscles relative to control, within a relatively short time period. Whole-genome analysis of RNA-Pol II binding to DNA by muscle-specific targeted DamID (TaDa) protocol revealed that muscle inactivity altered Pol II binding in 121 out of 2010 genes (6%), with a three-fold enrichment of genes coding for lncRNAs. The suppressed protein-coding genes included genes associated with longevity, DNA repair, muscle function, and ubiquitin-dependent proteostasis. Moreover, inducing muscle inactivation exerted a multi-level impact upon chromatin modifications, triggering an altered epigenetic balance of active versus inactive marks. The downregulated genes in the inactive muscles included genes essential for muscle structure and function, carbohydrate metabolism, longevity, and others. Given the multiple analogous genes in Drosophila for many human genes, extrapolating our findings to humans may hold promise for establishing a molecular link between sedentary behavior and metabolic diseases.