MAPT and Alzheimer disease: As Figure 1 shown: DNA methylation regulates the expression of AD-related genes under the action of related enzymes, accelerates the pathological process and aggravates the development of AD; (2) decreased histone methylation leads to synaptic transmission, neuronal growth and memory dysfunction; and (3) changes in related enzymes leads to a decrease in the level of histone acetylation, which leads to the inactivation of memory-related genes and abnormal phosphorylation of tau, resulting in cognitive degeneration.