Many of the significant genes have known mitochondrial functions, notably the mtDNA transcription factor TFAM (p = 1.09 × 10–29) and mitochondrial exonuclease MGME1 (p = 5.87 × 10–23), genes known as causal for mtDNA depletion syndromes (Stiles et al. 2016; Kornblum et al. 2013). This evidence concerns the gene TFAM and mitochondrial DNA depletion syndrome.