APP and early-onset autosomal dominant Alzheimer disease: The amyloid precursor protein (APP) is best known for its crucial role in Alzheimer’s disease pathogenesis (De Strooper and Karran, 2016; Haass and Selkoe, 2022), whereas its physiological functions are only beginning to be unraveled (Mockett et al., 2017; Müller et al., 2017).