Detection of 8-oxoG DNA glycosylase activity and OGG1 transcripts in the rat CNS

The oxoguanine DNA glycosylase (Ogg1) is a DNA repair enzyme that excises 7 ,8-dihydro-8-oxoguanine present in DNA damaged by oxidative stress. We have investigated the expression of the OGG1 gene in different regions of the r at CNS, Biochemical studies on brain homogenates of adult rats have shown t hat Ogg1 nicking activity is present at relatively similar levels in the ce rebral cortex, the hypothalamus, the pens and the cerebellum. Following in situ hybridization with radiolabeled OGG1 cDNA or specific antisense oligon ucleotides, OGG1 transcripts showed a widespread but heterogeneous distribu tion pattern among distinct brain regions of adult rats: high levels of thi s transcript were detected in the CA1-CA3 layers and the gyrus dentate of t he hippocampal formation, the piriform cortex, the supraoptic nuclei, the o livary complex as well as in the pyramidal cells of layer V of the cortex a nd the Purkinje cells of the cerebellum. In peripheral organs such as the l ungs, the stomach and the spleen, OGG1 transcript is however expressed in s pecific subpopulations of cells. Using a semi-quantitative reverse transcri ption - polymerase chain reaction assay on total mRNA from the frontal cort ex, OGG1 mRNA was determined to be expressed with relatively the same level s in 1-day-old and 7-day-old rats as well as in adult rats. These results p rovide evidence for the widespread expression of the OGG1 gene in developin g and adult brains. (C) 2000 Elsevier Science B.V. All rights reserved.