Downregulating Mitochondrial DNA Polymerase γ in the Muscle Stimulated Autophagy, Apoptosis, and Muscle Aging-Related Phenotypes in Drosophila Adults

Reactive oxygen species, generated as by-products of mitochondrial electron transport, can induce damage to mitochondrial DNA (mtDNA) and proteins. Here, we investigated whether the moderate accumulation of mtDNA damage in adult muscles resulted in accelerated aging-related phenotypes in Drosophila. DNA polymerase gamma (Pol gamma) is the sole mitochondrial DNA polymerase. The muscle-specific silencing of the genes encoding the polymerase subunits resulted in the partial accumulation of mtDNA with oxidative damage and a reduction in the mtDNA copy number. This subsequently resulted in the production of abnormal mitochondria with reduced membrane potential and, consequently, a partially reduced ATP quantity in the adult muscle. Immunostaining indicated a moderate increase in autophagy and mitophagy in adults with RNA interference of Pol gamma (Pol gamma RNAi) muscle cells with abnormal mitochondria. In adult muscles showing continuous silencing of Poly, malformation of both myofibrils and mitochondria was frequently observed. This was associated with the partially enhanced activation of pro-apoptotic caspases in the muscle. Adults with muscle-specific Pol gamma RNAi exhibited a shortened lifespan, accelerated age-dependent impairment of locomotor activity, and disturbed circadian rhythms. Our findings in this Drosophila model contribute to understanding how the accumulation of mtDNA damage results in impaired mitochondrial activity and how this contributes to muscle aging.

Automated summary

This study investigated whether moderate mtDNA damage in adult Drosophila muscles would accelerate aging. The accumulation of mtDNA damage was found to impair mitochondrial activity and contribute to muscle aging.