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Global transcriptomic profiling of ischemic/reperfusion injury in an in vivo Gpx1 -/- transgenic mouse model.

ABSTRACT: Glutathione peroxidase (Gpx) is a selenium-containing enzyme that catalyses the reduction of a variety of biological peroxides at the expense of reduced glutathione (GSH). Gpx1 is the most abundant isoform and its role has been implicated in neurodegenerative disorders such as Parkinson’s disease (PD), dementia with Lewy bodies tissue (DLB) (Power and Blumbergs, 2009) and traumatic brain injury (Tsuru-Aoyagi et al., 2009). Due to its high abundance, mutation of the Gpx1 allele would lower overall Gpx activity in the brain significantly. Gpx1 knockout (Gpx1-/-) mice do not show overt phenotypic differences, but all indications suggest that these mice are in a chronic “pro-oxidant” state (Cheng et al. 1999; de Haan et al. 2004). Indeed, a recent study from our laboratory illustrated that the absence of Gpx1 exacerbated stroke injury via increased ROS production and vascular permeability (Wong et al. 2008). Furthermore, Gpx1-/- mice demonstrated an increase in caspase-3 activation and greater infarct volume (Crack et al. 2001)

ORGANISM(S): Mus musculus

PROVIDER: GSE23162 | GEO | 2011/01/10

SECONDARY ACCESSION(S): PRJNA133271

REPOSITORIES: GEO

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Project description:The complexity of gene regulation has created obstacles to defining mechanisms that establish the patterns of gene expression characteristic of the different clinical phenotypes of breast cancer. Transcription factor TFAP2C plays a critical role in the regulation of both estrogen receptor-alpha (ERM-NM-1) and c-ErbB2/HER2 (Her2). Herein, we performed chromatin immunoprecipitation and direct sequencing (ChIP-seq) for TFAP2C in four breast cancer cell lines representing different clinical phenotypes. Comparing the genomic binding sites for TFAP2C in the various cell lines, we identified that glutathione peroxidase (GPX1) is regulated by TFAP2C through an AP-2 regulatory region in the promoter of the GPX1 gene. Knock-down of TFAP2C, but not the related factor TFAP2A, resulted in an abrogation of GPX1 expression. Selenium-dependent GPX activity correlated with endogenous GPX1 expression, and overexpression of exogenous GPX1 induced GPX activity and significantly increased resistance to tert-butyl hydroperoxide. Methylation of the CpG island encompassing the AP-2 regulatory region was identified in cell lines where TFAP2C failed to bind the GPX1 promoter and GPX1 expression was unresponsive to TFAP2C. Furthermore, in cell lines where GPX1 promoter methylation was associated with gene silencing, treatment with 5-aza-dC (an inhibitor of DNA methylation) resulted in activation of GPX1 RNA and protein expression. Methylation of the GPX1 promoter was identified in approximately 20% of primary breast cancers and a highly significant correlation between TFAP2C and GPX1 expression was confirmed when considering only those tumors with an unmethylated promoter, whereas the related factor, TFAP2A, failed to demonstrate a correlation. The results demonstrate that TFAP2C regulates the expression of GPX1, which influences the redox state and sensitivity to oxidative stress induced by peroxides. Given the established role of GPX1 in breast cancer, the results provide an important mechanism for TFAP2C to further influence oncogenesis and progression of breast carcinoma cells. 4 ChIP-Seq data for TFAP2C in human breast carcinoma cell lines MCF-7, BT-474, MDA-MB-453 and SKBR-3.

Project description:The complexity of gene regulation has created obstacles to defining mechanisms that establish the patterns of gene expression characteristic of the different clinical phenotypes of breast cancer. Transcription factor TFAP2C plays a critical role in the regulation of both estrogen receptor-alpha (ERα) and c-ErbB2/HER2 (Her2). Herein, we performed chromatin immunoprecipitation and direct sequencing (ChIP-seq) for TFAP2C in four breast cancer cell lines representing different clinical phenotypes. Comparing the genomic binding sites for TFAP2C in the various cell lines, we identified that glutathione peroxidase (GPX1) is regulated by TFAP2C through an AP-2 regulatory region in the promoter of the GPX1 gene. Knock-down of TFAP2C, but not the related factor TFAP2A, resulted in an abrogation of GPX1 expression. Selenium-dependent GPX activity correlated with endogenous GPX1 expression, and overexpression of exogenous GPX1 induced GPX activity and significantly increased resistance to tert-butyl hydroperoxide. Methylation of the CpG island encompassing the AP-2 regulatory region was identified in cell lines where TFAP2C failed to bind the GPX1 promoter and GPX1 expression was unresponsive to TFAP2C. Furthermore, in cell lines where GPX1 promoter methylation was associated with gene silencing, treatment with 5-aza-dC (an inhibitor of DNA methylation) resulted in activation of GPX1 RNA and protein expression. Methylation of the GPX1 promoter was identified in approximately 20% of primary breast cancers and a highly significant correlation between TFAP2C and GPX1 expression was confirmed when considering only those tumors with an unmethylated promoter, whereas the related factor, TFAP2A, failed to demonstrate a correlation. The results demonstrate that TFAP2C regulates the expression of GPX1, which influences the redox state and sensitivity to oxidative stress induced by peroxides. Given the established role of GPX1 in breast cancer, the results provide an important mechanism for TFAP2C to further influence oncogenesis and progression of breast carcinoma cells.

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Global transcriptomic profiling of ischemic/reperfusion injury in an in vivo Gpx1 -/- transgenic mouse model.

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