Presenilin 1-related alterations in DNA integrity in a transgenic mouse model of Alzheimer's disease

The present study tested the hypothesis that mutations in amyloid precursor protein (APP) and presenilin (PS) 1 result in alterations in the amount of nuclear (n) DNA repair and nDNA damage in neurons in vivo. To this end, the relative amount of nDNA repair was measured in 8-month-old transgenic mice expressing either human mutant APP (APP751(SL) mice), human mutant PS1 (pS1(M146L) mice) or both human mutant APP and PS1 (APP751(SL)/PS1(M146L) mice) with unscheduled DNA synthesis, and the relative amount of nDNA single strand breaks (SSB) with in situ nick translation. APP751(SL)/PS1(M146L) mice showed a significantly decreased relative amount of nDNA repair in pyramidal cells in hippocampal area CA1/2 compared to APP751(SL) mice. Furthermore, PS1(M146L) mice showed a significantly increased relative amount of nDNA SSB in both granule cells in the dentate gyrus and pyramidal cells in area CA1/2 compared to both APP751(SL) mice and APP751(SL)/PS1(M146L) mice. These results might indicate a previously unknown action of mutations in PS1 on DNA integrity, which might be involved in the pathophysiologic processes of mutant PS1 in Alzheimer's disease. (C) 2009 Elsevier B.V. All rights reserved.