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Publication - Dr Karen Mifsud

    Rapid down‐regulation of glucocorticoid receptor gene expression in the dentate gyrus after acute stress in vivo

    Role of DNA Methylation and microRNA Activity

    Citation

    Mifsud, KR, Saunderson, EA, Spiers, H, Carter, SD, Trollope, AF, Mill, J & Reul, JMHM, 2016, ‘Rapid down‐regulation of glucocorticoid receptor gene expression in the dentate gyrus after acute stress in vivo: Role of DNA Methylation and microRNA Activity’. Neuroendocrinology, vol 104., pp. 157-169

    Abstract

    Background: Although glucocorticoid receptors (GRs) in the hippocampus play a vital role in the regulation of physiological and behavioural responses to stress, the regulation of receptor expression remains unclear. This work investigates the molecular mechanisms underpinning stress-induced changes in hippocampal GR mRNA levels in vivo.

    Methods: Male Wistar rats were killed either under baseline conditions or after forced swim stress (FSS; 15 min in 25°C water). Rat hippocampi were micro-dissected (for mRNA, microRNA, and DNA methylation analysis) or frozen whole (for chromatin immunoprecipitation (ChIP). In an additional experiment, rats were pre-treated with RU486 (a GR antagonist) or vehicle.

    Results: FSS evoked a dentate gyrus-specific reduction in GR mRNA levels. This was associated with increased DNMT3a protein association with a discreet region of the Nr3C1 (GR gene) promoter, shown here to undergo increased DNA methylation after FSS. FSS also caused a time-dependent increase in the expression of miR-124a, a microRNA known to reduce GR mRNA expression, which was inversely correlated with a reduction in GR mRNA levels at 30 min post-FSS. FSS did not affect GR binding to a putative negative glucocorticoid response element (GRE) within the Nr3c1 gene.

    Conclusions: Acute stress results in decreased GR mRNA expression specifically in the dentate gyrus. Our results indicate that a complex interplay of multiple molecular mechanisms including increased DNA methylation of discrete CpG residues within the Nr3c1 gene, most likely facilitated by DNMT3a, and increased expression of miR-124a could be responsible for these changes.

    Full details in the University publications repository