Background: Amyloid-β42 oligomers (Aβ42O), the proximate effectors of
neurotoxicity observed in Alzheimer’s disease (AD), can induce mitochondrial oxidative stress
and impair mitochondrial function besides causing mitochondrial DNA (mtDNA) damage.
Aβ42O also regulate the proliferative and differentiative properties of stem cells.
Objective: We aimed to study whether Aβ42O-induced mtDNA damage is involved in the
stem cell differentiation.
Method: Human iPSCs-derived neural stem cell (NSC) was applied to investigate the effect
of Aβ42O on
reactive oxygen species (ROS) production and DNA damage using mitoSOX staining and
PCR lesion assay, respectively. mtDNA repair activity was measured by non-homologous end
(NHEJ) in vitro assay using mitochondria isolates and the expression and localization of
NHEJ components were determined by Western blot and immunofluorescence assay. The
expressions of Tuj-1 and GFAP, detected by immunofluorescence and qPCR, respectively,
were examined as an index of neurons and astrocytes production.
Results: We show that in NSC Aβ42O treatment induces ROS production and mtDNA
damage and impairs DNA end joining activity. NHEJ components, such as Ku70/80, DNA-
PKcs, and XRCC4, are localized in mitochondria and silencing of XRCC4 significantly
exacerbates the effect of Aβ42O on
mtDNA integrity. On the contrary, pre-treatment with Phytic Acid (IP6), which specifically
DNA-PK-dependent end-joining, inhibits Aβ42O-induced mtDNA damage and neuronal
Conclusion: Aβ42O-induced mtDNA repair impairment may change cell fate thus shifting
differentiation toward an astrocytic lineage. Repair stimulation counteracts Aβ42O
neurotoxicity, suggesting mtDNA repair pathway as a potential target for the treatment of
neurodegenerative disorders like AD.