MT-CO1 and myopathy: Next, we compared the expression of selected mtDNA-encoded genes (CYTB, COX1, ND1, and ND6) (Figure 6A–D) and nuclear-encoded genes involved in mitochondrial biogenesis (PPARGC1A and transcription factor A (TFAM)) (Figure 6E,F) in skin fibroblasts from healthy controls versus those from myopathy patients.