DNA methylation changes are present in AD-related genes; some of these genes are hypermethylated (MTHFR, Neprilysin, MAPT, APOE, SORB3), while others—including those required for the production of the Aβ peptide—have been found to be hypomethylated (APP, BACE, PSEN1, PP2A, S100A2, CREB5) [336,337]. The gene discussed is PSEN1; the disease is Alzheimer disease.