Amyloid-β E22Δ variant induces synaptic alteration in mouse hippocampal slices

We recently identified a novel amyloid precursor protein mutation (E693Delta) in familial Alzheimer's-type dementia. This mutation produces amyloid-beta (Abeta) variant lacking glutamate-22 (E22Delta), which showed enhanced oligomerization but no fibrillization. Here, we examined in-vitro toxicity of Abeta E22Delta peptide. Wild-type Abeta1-42 showed a dose-dependent (1 nM to 1 microM) cytotoxicity to cultured neuronal cells in the 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyl tetrazolium bromide assay, whereas Abeta1-42 E22Delta was toxic only weakly at 1 microM. In mouse hippocampal slices, however, Abeta1-42 E22Delta caused a dose-dependent (0.1-10 microM) decrease of synaptophysin, whereas wild-type Abeta1-42 was trophic at 0.1-1 microM and toxic at 10 microM. These results suggest that extracellular Abeta E22Delta causes more potent synaptic alteration, but lower neurodegeneration, than wild-type Abeta probably because of its unique aggregation property.