PSEN1 and Alzheimer disease: Since wild-type mice do not develop age-associated amyloid pathology, we next crossed Psen1KI/KI mice with 5xFAD mice, an accelerated model of AD that displays severe amyloid pathology [46] (5xFAD * Psen1KI/KI mouse was hemizygous for FAD mutations and homozygous for Psen1KI/KI).