PNPT1 and mitochondrial DNA depletion syndrome, encephalomyopathic form with methylmalonic aciduria: Although this study uses MEFs, it is interesting to note that the change in these particular genes correlate with the lack of PNPase expression relative to their TM6 and rho0 MEF counterparts, since PNPase mutations are linked to delayed myelination, hearing loss, encephalomyopathy, gut disturbances, and chorioretinal defects in humans [45–50].