Profiling of stress-induced epigenetic alterations in neuronal Neuro-2a cells

Epigenetic processes participate in the transmission of environmental cues into chromatin conformation changes governing permanently altered gene expression. We analyzed stress induced alterations of transcription profiles that might be maintained by chromatin modifications such as histone acetylation and CpG methylation. Using N2a cells that lack glucocorticoid receptors (GR), we identified dexamethasone regulated genes by Illumina MicroArray after ectopical expression of GR. In addition, we surveyed the transcription profile of N2a cells with pharmacologically inhibited DNMT (5AZA) as well as HDAC (Trichostatin A, TSA), and built convergent expression profiles from all three arrays. From 710 Dex-stimulated genes, 185 genes were up-regulated by TSA. The 5AZA/Dex intersection resulted in an overlap of only 1.4%. Commonly upregulated candidates from all three arrays comprised chromogranin A, NPY, serum/glucocorticoid kinase and metallothionein-1. Furthermore, chromatin immunoprecipitation analysis was performed to monitor stress or TSA-induced epigenetic modifications of the target promoters with focus on the acetylation status of histone H4 (AcH4). Preliminary results indicate subtle changes in the AcH4 composition after TSA, and to a smaller extent also after Dex exposure. Establishment of a GR-ChIP analysis will allow us to directly correlate GR binding sites with epigenetic changes of promoters, providing new insights into the mechanisms of long lasting stress effects.