DNMT1 and Alzheimer disease: Among the major DNMTs, DNMT1 isconsidered the maintenance methylase, and DNMT3a and DNMT3b are considered denovo methylases.16 DNMT3a and DNMT3b are of particular interest in thecontext of the topic of this review as they introduce methylation marks to DNAover time; however, studies exploring these enzymes in AD mouse models reportedconflicting findings (Table 2).42,44,45 For example, studies investigating DNMT1 expressionreported either a decrease in hippocampal expression in AD mice,42,45 or nosignificant changes44 (Table 2).