Disease-Specific Phenotypes Inipsc-Derived Neural Stem Cells Withpolgmutations

Mutations inPOLGdisrupt mtDNAreplication and cause devastating diseases often with neurological phenotypes. Defining disease mechanisms has been hampered by limited access to human tissues, particularly neurons. Using patient cells carryingPOLGmutations, we generatediPSCs and then neural stem cells. These neural precursors manifested a phenotype that faithfully replicated the molecular and biochemical changes found in patient post-mortem brain tissue. We confirmed the same loss of mtDNAand complex I in dopaminergic neurons generated from the same stem cells.POLG-driven mitochondrial dysfunction led to neuronalROSoverproduction and increased cellular senescence. Loss of complex I was associated with disturbedNAD(+)metabolism with increasedUCP2 expression and reduced phosphorylated SirT1. In cells with compound heterozygousPOLGmutations, we also found activated mitophagy via theBNIP3 pathway. Our studies are the first that show it is possible to recapitulate the neuronal molecular and biochemical defects associated withPOLGmutation in a human stem cell model. Further, our data provide insight into how mitochondrial dysfunction and mtDNAalterations influence cellular fate determining processes.