APP and Alzheimer disease: Alzheimer’s disease at the early stage is caused by increased production of the AβPP-derived peptide Aβ42 with the growth in mutations in the amyloid-β protein precursor gene (AβPP), the presenilin 1 gene (PSEN1), or the presenilin 2 gene (PSEN2) (Younkin, 1998; Renner et al., 2010; Hansson et al., 2019).