PSEN1 and early-onset autosomal dominant Alzheimer disease: Many transgenic mouse lines are produced as animal models of Alzheimer’s disease (AD), with the majority being engineered to overexpress mutant β-amyloid precursor protein (APP) and/or presenilin 1 or 2 (PS1, PS2) genes identified from patients with early-onset familial AD (FAD) [1–3].