APP and Alzheimer disease: In the brain, epigenetic studies suggest robust associations between DNAm and AD (11), including differential DNAm in the amyloid precursor protein (APP) (12), microtubule-associated protein tau (MAPT) (12), apolipoprotein (APOE) promoter region (13), homeobox A3 (HOXA3) (14), interleukin-1 beta (IL-1β) (15), interleukin-6 (IL-6) (15), and claudin-5 (CLDN5) genes (16).