APP and Alzheimer disease: Presence of a third copy of a portion of chromosome 21 (Hsa21) in DS results in overexpression of several genes, including the amyloid precursor protein (APP), which causes AD pathologies such as neuroinflammation, neuronal cell loss, amyloid plaques, and neurofibrillary tangles (NFTs) (Hartley et al., 2015; Delabar et al., 2016).