Abstract
BACKGROUND: Recent research in Alzheimer's disease (AD) field has been focused on the potential role of the amyloid-β protein that is derived from the transmembrane amyloid precursor protein (APP) in directly mediating cognitive impairment in AD. Transgenic mouse models overexpressing APP develop robust AD-like amyloid pathology in the brain and show various levels of cognitive decline. In the present study, we examined the cognition of the BRI2-Aβ transgenic mouse model in which secreted extracellular Aβ1-40, Aβ1-42 or both Aβ1-40/Aβ1-42 peptides are generated from the BRI-Aβ fusion proteins encoded by the transgenes. BRI2-Aβ mice produce high levels of Aβ peptides and BRI2-Aβ1-42 mice develop amyloid pathology that is similar to the pathology observed in mutant human APP transgenic models. RESULTS: Using established behavioral tests that reveal deficits in APP transgenic models, BRI2-Aβ1-42 mice showed completely intact cognitive performance at ages both pre and post amyloid plaque formation. BRI2-Aβ mice producing Aβ1-40 or both peptides were also cognitively intact. CONCLUSIONS: These data indicate that high levels of Aβ1-40 or Aβ1-42, or both produced in the absence of APP overexpression do not reproduce memory deficits observed in APP transgenic mouse models. This outcome is supportive of recent data suggesting that APP processing derivatives or the overexpression of full length APP may contribute to cognitive decline in APP transgenic mouse models. Alternatively, Aβ aggregates may impact cognition by a mechanism that is not fully recapitulated in these BRI2-Aβ mouse models.