A specific amyloid-β protein assembly in the brain impairs memory
Sylvain Lesne, Ming Teng Koh, Linda Kotilinek, Rakez Kayed, Charles G. Glabe, Austin Yang, Michela Gallagher & Karen H. Ashe
Nature (2006) Vol. 440, No. 16, 352-357

ABSTRACT:  Memory function often declines with age1, and is believed to deteriorate initially because of changes in synaptic function rather than loss of neurons. Some individuals then go on to develop Alzheimer’s disease with neurodegeneration. Here we use Tg2576 mice, which express a human amyloid-b precursor protein (APP) variant linked to Alzheimer’s disease, to investigate the cause of memory decline in the absence of neurodegeneration or amyloid-b protein amyloidosis. Young Tg2576 mice (<6 months old) have normal memory and lack neuropathology, middle-aged mice (6–14 months old) develop memory deficits without neuronal loss, and old mice (>14 months old) form abundant neuritic plaques containing amyloid-b. We found that memory deficits in middle-aged Tg2576 mice are caused by the extracellular accumulation of a 56-kDa soluble amyloid-b assembly, which we term Ab*56 (Ab star 56). Ab*56 purified from the brains of impaired Tg2576 mice disrupts memory when administered to young rats. We propose that Ab*56 impairs memory independently of plaques or neuronal loss, and may contribute to cognitive deficits associated with Alzheimer’s disease.