C. elegans miro-1 Mutation Reduces the Amount of Mitochondria and Extends Life Span.

Mitochondria play a critical role in aging, however, the underlying mechanism is not well understood. We found that a mutation disrupting the C. elegans homolog of Miro GTPase (miro-1) extends life span. This phenotype requires simultaneous loss of miro-1 from multiple tissues including muscles and neurons, and is dependent on daf-16/FOXO. Notably, the amount of mitochondria in the miro-1 mutant is reduced to approximately 50% of the wild-type. Despite this reduction, oxygen consumption is only weakly reduced, suggesting that mitochondria of miro-1 mutants are more active than wild-type mitochondria. The ROS damage is slightly reduced and the mitochondrial unfolded protein response pathway is weakly activated in miro-1 mutants. Unlike previously described long-lived mitochondrial electron transport chain mutants, miro-1 mutants have normal growth rate. These results suggest that the reduction in the amount of mitochondria can affect the life span of an organism through activation of stress pathways.