Mutations in the gene encoding APP and presenilin (PSEN1, PSEN2), the catalytic subunit of γ-secretase, are associated with the early-onset familial forms of Alzheimer's disease (AD; Goate et al., 1991; Levy-Lahad et al., 1995; Sherrington et al., 1995). This evidence concerns the gene PSEN2 and Alzheimer disease.