Expression profiling of mouse embryonic fibroblasts with a deletion in the helicase domain of the Werner Syndrome gene homologue treated with hydrogen peroxide

Background: Werner Syndrome (WS) is a rare disorder characterized by the premature onset of a number of age-related diseases. The gene responsible for WS encodes a DNA helicase/exonuclease protein believed to affect different aspects of transcription, replication, and/or DNA repair. In addition to genomic instability, human WS cells exhibit oxidative stress. In this report, we have examined the impact of exogenous hydrogen peroxide on the expression profile of mouse embryonic fibroblasts lacking part of the helicase domain of the WRN homologue (here referred to as Wrn(Delta hel/Delta hel)). Results: Wrn(Delta hel/Delta hel) mutant mouse embryonic fibroblasts exhibit increased oxidative stress. This was reflected by increased intracellular reactive oxygen species (ROS), increased oxidative damage in genomic DNA, changes in ATP/ADP ratios, and a disruption of the inner mitochondrial transmembrane potential when compared to wild type mouse embryonic fibroblasts. Expression profile analyses of hydrogen peroxide-treated wild type cells have indicated significant decreases in the expression of genes involved in mitosis, glycolysis, fatty acid metabolism, nucleic acid metabolism, and cell cycle control, as well as protein modification and stability. Such decreases in these biological processes were not observed in hydrogen peroxide-treated Wrn(Delta hel/Delta hel) cells. Importantly, untreated Wrn(Delta hel/Delta hel) cells already exhibited down regulation of several biological processes decreased in wild type cells that had been treated with hydrogen peroxide. Conclusion: Expression profiling of Wrn(Delta hel/Delta hel) mutant cells revealed a very different response to exogenous addition of hydrogen peroxide in culture compared to wild type cells. This is due in part to the fact that Wrn(Delta hel/Delta hel) mutant cells already exhibited a modest chronic intracellular oxidative stress.