Electron transport chain complex I and mitochondrial fusion regulate ROS for differentiation in Drosophila neural stem cells

Mitochondrial fusion and electron transport chain complex I are each essential for differentiation in Drosophila neuroblasts, but the mechanism by which they interact to mediate differentiation is unknown. We found that complex I subunit depletion did not affect type II neuroblast numbers but reduced their proliferation and decreased their lineage cells. Complex I depletion decreased the mitochondrial membrane potential and cristae numbers, increased fragmentation and ROS, and inhibited Notch signaling in lineage cells. Similarly, antioxidant enzyme depletion increased ROS and reduced lineage cells. Both complex I and antioxidant proteins promoted the G1/S transition and nuclear cyclin E levels. Additional mitochondrial fusion via Drp1 mutants restored ROS levels, proliferation, and differentiation defects in complex I and antioxidant protein-depleted neuroblasts. Overexpression of antioxidant proteins and an increase in Notch signaling alleviated ROS and the complex I depletion-driven defect in neuroblast proliferation and differentiation. Complex I and mitochondrial fusion together restrict ROS to support neuroblast proliferation and differentiation.