Mitochondrial DNA integrity is essential for mitochondrial maturation during differentiation of neural stem cells

Differentiation of neural stem cells (NSCs) involves the activation of aerobic metabolism, which is dependent on mitochondrial function. Here, we show that the differentiation of NSCs involves robust increases in mitochondrial mass, mitochondrial DNA (mtDNA) copy number, and respiration capacity. The increased respiration activity renders mtDNA vulnerable to oxidative damage, and NSCs defective for the mitochondrial 8-oxoguanine DNA glycosylase (OGG1) function accumulate mtDNA damage during the differentiation. The accumulated mtDNA damages in ogg1(-/-) cells inhibit the normal maturation of mitochondria that is manifested by reduced cellular levels of mitochondrial encoded complex proteins (complex I [cI], cIII, and cIV) with normal levels of the nuclear encoded cII present. The specific cI activity and inner membrane organization of respiratory complexes are similar in wt and ogg1(-/-) cells, inferring that mtDNA damage manifests itself as diminished mitochondrial biogenesis rather than the generation of dysfunctional mitochondria. Aerobic metabolism increases during differentiation in wild-type cells and to a lesser extent in ogg1(-/-) cells, whereas anaerobic rates of metabolism are constant and similar in both cell types. Our results demonstrate that mtDNA integrity is essential for effective mitochondrial maturation during NSC differentiation.