Rapid down-regulation of glucocorticoid gene expression in the dentate Gyrus after acute stress in vivo: role of DNA methylation and microRNA activity

Mifsud, Karen R., Saunderson, Emily A., Spiers, Helen, Carter, Sylvia D., Trollope, Alexandra F., Mill, Jonathon, and Reul, Johannes M.H.M. (2016) Rapid down-regulation of glucocorticoid gene expression in the dentate Gyrus after acute stress in vivo: role of DNA methylation and microRNA activity. Neuroendocrinology, 104 (2). pp. 157-169.

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View at Publisher Website: http://dx.doi.org/10.1159/000445875
 
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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.

Item ID: 43636
Item Type: Article (Refereed Research - C1)
Keywords: PTSD, epigenetics, DNA methylation, microRNA, forced swimming, Chromatin immunoprecipitation
ISSN: 1423-0194
Funders: Biotechnology and Biological Sciences Research Council (BBSRC), Medical Research Council (MRC), British Pharmacological Society
Projects and Grants: BBSRC grant BB/K007408/1, BBSRC grant BB/G02507X/1
Date Deposited: 07 Jun 2016 00:48
FoR Codes: 11 MEDICAL AND HEALTH SCIENCES > 1109 Neurosciences > 110904 Neurology and Neuromuscular Diseases @ 50%
06 BIOLOGICAL SCIENCES > 0604 Genetics > 060404 Epigenetics (incl Genome Methylation and Epigenomics) @ 50%
SEO Codes: 92 HEALTH > 9201 Clinical Health (Organs, Diseases and Abnormal Conditions) > 920111 Nervous System and Disorders @ 100%
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