Loss of neuronal cell cycle control as a mechanism of neurodegeneration in the presenilin-1 Alzheimer's disease brain.

Presenilin-1 (PS1) is a component of the beta-catenin degradation machinery, and PS1 mutations linked to familial Alzheimer's disease (FAD) represent a loss of this function, leading, in non-neuronal cells, to accumulation of cyclin D1, aberrant cell cycle activation and hyperproliferation. In post-mitotic neurons, cell cycle activation is thought to be abortive and initiate apoptosis, thus contributing to AD pathogenesis. Consequently, we tested here the hypothesis that, in the PS1 FAD brain, cyclin D1 accumulation may occur and lead to neuronal apoptosis secondary to an abortive entry into the cell cycle.