APP and Alzheimer disease: Less than 5% of all AD-cases belong to FAD which is caused by mutations in the genes encoding for APP and the presenilins (PS) 1 and 2, proteins involved in proteolytic APP-processing (Levy et al., 1990; Goedert et al., 1994; Levy-Lahad et al., 1995; Sherrington et al., 1995; Tanzi, 2012).