DNMT1 and Alzheimer disease: However, a decline in global DNA methylation was found in the autopsied hippocampus of patients with AD [20,21].Moreover, Guo’s study indicated that histone H3 hyperacetylation and DNMT-dependent hypomethylation mediate the stress-related signaling pathways activation in SH-SY5Y cells, which lead to APP, PSEN1, and BACE1 genes expression increase, thus leading to Aβ overproduction [22].