Transcriptome analysis indicates processes related to axonogenesis (FDR = 4.49 x 10−3), axon development (FDR = 4.74 x 10−3), and axonal guidance (FDR = 4.74 x 10−3) were overrepresented in PKO cells, consistent with previous studies detailing causative PNPase mutations in delayed myelination, hearing loss, encephalomyopathy, and chorioretinal defects in humans. The gene discussed is PNPT1; the disease is mitochondrial DNA depletion syndrome, encephalomyopathic form with methylmalonic aciduria.