APP and familial Alzheimer disease: In the attempt to recapitulate the sequence of altered events occurring in brain circuits along with AD progression, a common strategy is to employ transgenic (tg) AD mouse models expressing human proteins carrying mutations associated to familial AD (FAD), especially those involved in Aβ production: the amyloid precursor protein (APP), presenilin 1 (PS1) and presenilin 2 (PS2)9.