PSEN1 and Alzheimer disease: Importantly, this enhanced neurogenesis mitigates neuronal loss in Alzheimer’s disease (AD) mice such as 5xFAD mice, which exhibit neurodegeneration because of excessive amyloid deposition resulting from overexpressed mutant amyloid precursor protein and presenilin-1 (6, 8), and PS19 mice, which overexpress mutant tau protein and show broad neuronal loss (9, 10).