APP and Alzheimer disease: Studies carried out on human brain tissue as well as transgenic mouse models of AD have revealed that the swollen axons around Aβ aggregates are enriched in the amyloid precursor protein (APP) and BACE1, the β-secretase involved in the amyloidogenic processing of APP (Cras et al., 1991; Cummings et al., 1992; Kandalepas et al., 2013; Yoon et al., 2013; Gowrishankar et al., 2015).