APP and early-onset autosomal dominant Alzheimer disease: We used an Aβ-overexpressing transgenic mouse model of Alzheimer's disease, TASTPM mice that carry a double mutation on the amyloid precursor protein (APP) and one single mutation on the presenilin-1 gene causing prevalent amyloid plaque deposition before they are six months old.15,16 Aβ deposits within the histological sections of the fixed brain hippocampus from TASTPM mice were analysed.