PSEN2 and familial Alzheimer disease: Although wild-type mice do not form senile plaques or neurofibrillary tangles,16 genetically engineered mice consisting of familial AD (FAD)-linked mutations in genes such as amyloid precursor protein (APP), presenilin1 (PSEN1), and PSEN2 are employed to mimic amyloidosis features of FAD-AD.17