Genetic mutations in the APP gene or presenilin-1 and presenilin-2 (PS1, PS2) genes, which encode for proteins constituting essential parts of the γ-secretase complex [8], were found in early onset cases of familial AD (FAD) and are responsible for an enhanced Aβ production and deposition in plaques [9]. Here, PSEN2 is linked to familial Alzheimer disease.