Transgenic expression of human wild-type amyloid precursor protein decreases neurogenesis in the adult hippocampus.

Besides its role in Alzheimer's disease, the amyloid precursor protein (APP) is implicated in several physiological functions in neuronal tissue such as cell survival, neurite outgrowth, synaptic formation, and neuronal plasticity. The present study analyzed effects of human wild-type APP (hAPP) overexpression on adult hippocampal neurogenesis in transgenic mice. Mice were housed under either standard or enriched conditions, the latter to boost neurogenetic activity. Different aspects of neurogenesis including proliferation, survival, and differentiation were assessed by employing the BrdU-incorporation method and, in parallel, immunohistochemistry for the neuronal and glial markers NeuN and S100b, respectively. Overexpression of hAPP caused a significant decrease in cell proliferation under standard housing conditions. The relative increase in the proliferation rate following housing in enriched environment was not different to that observed in wild-type mice. Overexpression of hAPP, on the other hand, promoted the survival of newly generated cells, but just under conditions of standard housing. Findings further suggest that overexpression of hAPP suppresses the phenotypic shift toward neuronal differentiation under conditions of enriched environment. In summary, the results reveal a dual effect of APP on adult hippocampal neurogenesis, comprising antiproliferative and prosurvival activities. Copyright 2009 Wiley-Liss, Inc.