PSEN1 and familial Alzheimer disease: Human genetic investigations have demonstrated that mutations in amyloid precursor protein (APP), presenilin 1 (PSEN1), or presenilin 2 (PSEN2) genes – all of which are involved in the generation of Aβ, are the cause of autosomal dominant familial Alzheimer’s disease (FAD) (Selkoe and Hardy, 2016; Jansen et al., 2019).