PSEN1 and Alzheimer disease: These include the Apolipoprotein E gene (ApoE) which increases the risk of developing AD (Corder et al., 1993), the Amyloid precursor protein (APP) (Goate et al., 1991), presenilin-1 (PSEN1), and presenilin-2 (PSEN2) (Levy-Lahad et al., 1995; Rogaev et al., 1995).