APP and Alzheimer disease: Pathological mutations in APP gene, PSEN1 gene or PSEN2 gene, APP duplication and trisomy of chromosome 21 promote Aβ production and neuronal apoptosis contributing to the pathogenesis of early-onset AD (Steiner et al., 1998; Wu and Song, 2013; Sun et al., 2014; Wu et al., 2015; Zhang et al., 2017; Zhang S. et al., 2018).