Indeed, in individuals belonging to families with segregate ALS-linked mutations, we observed that individual carriers of SOD1 and C9orf72 mutations had significantly higher levels of the mtDNA copy number than noncarriers of ALS-linked mutations, but only SOD1 mutation carriers showed a significant reduction in D-loop methylation levels [96]. The gene discussed is C9orf72; the disease is amyotrophic lateral sclerosis.