Sedentary behavior may accelerate aging through impact on epigenome and transcriptome: lessons from muscle inactivation in Drosophila larvae
AimThe biological mechanisms linking sedentary lifestyles and metabolic derangements are incompletely understood. Our animal model mimics sedentary behavior during early life, enabling us to explore the associated chromatin epigenetic and transcriptomic landscapes. MethodsDrosophila larvae carrying a temperature-sensitive mutation in the shibire1 (shi) gene were used. shi homozygous mutant larvae undergo instant arrest of muscle contraction at a restrictive temperature (30{degrees}C), without affecting other systems. Both shi and control (y,w) larvae were held at permissive temperature (18{degrees}C), and transferred to restrictive temperature (30{degrees}C) for six hours. Larvae were then dissected, fixed, and double-labeled with antibodies specific for epigenetic marks of chromatin activation (H3K9ac) and repression (H3K27me3), and their fluorescence signal was quantified. In addition, whole genome analysis of RNA-Pol II binding to DNA in muscle-specific inactive, or control larvae was performed using muscle-specific targeted DamID (TaDa) protocol. ResultsInducing muscle inactivity in shi larvae at 300C yielded a significantly higher ratio between chromatin activation and repression, based upon H3K9ac/H3K27me3 signals (p=0.025), relative to all control groups for which this ratio was comparable (p=0.995). Furthermore, muscle inactivation led to altered Pol II binding to 121 out of 2010 genes (6%). The suppressed protein-coding genes included genes associated with longevity, DNA repair, muscle function, and ubiquitin-dependent proteostasis. In addition, a three-fold enrichment of genes coding for lncRNAs was noted in the muscle-inactive larvae. ConclusionInducing muscle inactivation exerted a multi-level impact upon chromatin, triggering an altered epigenetic balance, as well as downregulation of the transcriptional activity of genes essential for muscle function, carbohydrate metabolism, longevity and others. Extrapolating these findings to humans holds promise for establishing a molecular link between sedentary behavior and metabolic diseases.