Neuronal Overexpression of Nogo Receptor 1 in APPswe/PSEN1(ΔE9) Mice Impairs Spatial Cognition Tasks without Influencing Plaque Formation

Abstract

In the search for molecules that may alter the formation of amyloid-β (Aβ) protofibrils, it has been shown that the Nogo-system can interact and bind to amyloid-β protein precursor and thus affect the amount of Aβ that is formed and deposited in the brain. To further address this issue in vivo, we crossed mice that overexpress Nogo receptor 1 (NgR1), “MemoFlex”, in forebrain neurons, with plaque forming APPswe/PSEN1(ΔE9) mice, to investigate if increased levels of NgR1 would influence plaque load or cognitive function in the resulting MemoFlex/APPswe/PSEN1(ΔE9) transgenic mice. We used a radial arm water maze and the Morris water maze to measure cognitive function. We did not find any significant effect of NgR1 overexpression on the performance of APPswe/PSEN1(ΔE9) mice in the radial arm water maze test. However, MemoFlex/APPswe/PSEN1(ΔE9) mice were found to be significantly impaired in the Morris water maze. We also analyzed the amount of plaques in the two mouse models without finding any significant difference in plaque load in the cerebral cortex or the hippocampal formation. It therefore appears that overexpression of NgR1 in APPswe/PSEN1(ΔE9) mice does not have any marked effects on Aβ levels, yet appears to impair spatial cognitive abilities. We conclude that strong overexpression of NgR1 in forebrain neurons impairs aspects of cognitive function but does not markedly alter plaque load in plaque-forming APPswe/PSEN1(ΔE9) mice. Thus high levels of membrane-bound NgR1 present since early postnatal life does not influence the development of plaques in mice carrying the two human plaque-causing mutations APPswe and PSEN1(ΔE9).