APP and early-onset autosomal dominant Alzheimer disease: The amyloid-β peptide 1–42 formed during proteolytic processing of the amyloid precursor protein (APP) is considered as a key player in the development or progression of Alzheimer’s disease (AD) and other pathologies associated with the formation of protein aggregates in the central nervous system ([1,2,3,4,5,6,7,8] and many others).