PSEN1 and familial Alzheimer disease: For this study, we examined 5xFAD mice [13] that carry three mutations in heterologous amyloid precursor protein (APP) and two in the Presenilin 1 (PS1) transgene which are responsible for the early onset of familial AD (FAD) and thereby display an aggressive version of AD-like pathology with phenotypes observed at the age of 1.5 months [14].