DNMT1 and Alzheimer disease: On the one hand, when mtDNA is exposed to oxidative stress, it activates the transcription factors NRF1 and PGC1‐α, which promote the expression of the mitochondrial methyltransferase DNMT1, which in turn hypermethylates genes in mtDNA, mainly those encoding cytochrome B (CytB), cyclooxygenase‐2 (COX‐2), and 12S ribosomal RNA (rRNA) in AD patients, thereby suppressing gene expression.67, 68