Tissue specific glucocorticoid receptor expression, a role for alternative first exon usage?

Context is key: glucocorticoid receptor and corticosteroid therapeutics in outcomes after traumatic brain injury

Traumatic brain injury (TBI) is a global health burden, and survivors suffer functional and psychiatric consequences that can persist long after injury. TBI induces a physiological stress response by activating the hypothalamic-pituitary-adrenal (HPA) axis, but the effects of injury on the stress response become more complex in the long term. Clinical and experimental evidence suggests long lasting dysfunction of the stress response after TBI. Additionally, pre- and post-injury stress both have negative impacts on outcome following TBI. This bidirectional relationship between stress and injury impedes recovery and exacerbates TBI-induced psychiatric and cognitive dysfunction. Previous clinical and experimental studies have explored the use of synthetic glucocorticoids as a therapeutic for stress-related TBI outcomes, but these have yielded mixed results. Furthermore, long-term steroid treatment is associated with multiple negative side effects. There is a pressing need for alternative approaches that improve stress functionality after TBI. Glucocorticoid receptor (GR) has been identified as a fundamental link between stress and immune responses, and preclinical evidence suggests GR plays an important role in microglia-mediated outcomes after TBI and other neuroinflammatory conditions. In this review, we will summarize GR-mediated stress dysfunction after TBI, highlighting the role of microglia. We will discuss recent studies which target microglial GR in the context of stress and injury, and we suggest that cell-specific GR interventions may be a promising strategy for long-term TBI pathophysiology.

Differential susceptibility of male and female germ cells to glucocorticoid-mediated signaling

While physiologic stress has long been known to impair mammalian reproductive capacity through hormonal dysregulation, mounting evidence now suggests that stress experienced prior to or during gestation may also negatively impact the health of future offspring. Rodent models of gestational physiologic stress can induce neurologic and behavioral changes that persist for up to three generations, suggesting that stress signals can induce lasting epigenetic changes in the germline. Treatment with glucocorticoid stress hormones is sufficient to recapitulate the transgenerational changes seen in physiologic stress models. These hormones are known to bind and activate the glucocorticoid receptor (GR), a ligand-inducible transcription factor, thus implicating GR-mediated signaling as a potential contributor to the transgenerational inheritance of stress-induced phenotypes. Here, we demonstrate dynamic spatiotemporal regulation of GR expression in the mouse germline, showing expression in the fetal oocyte as well as the perinatal and adult spermatogonia. Functionally, we find that fetal oocytes are intrinsically buffered against changes in GR signaling, as neither genetic deletion of GR nor GR agonism with dexamethasone altered the transcriptional landscape or the progression of fetal oocytes through meiosis. In contrast, our studies revealed that the male germline is susceptible to glucocorticoid-mediated signaling, specifically by regulating RNA splicing within the spermatogonia, although this does not abrogate fertility. Together, our work suggests a sexually dimorphic function for GR in the germline, and represents an important step towards understanding the mechanisms by which stress can modulate the transmission of genetic information through the germline.

Differential susceptibility of male and female germ cells to glucocorticoid-mediated signaling

While physiologic stress has long been known to impair mammalian reproductive capacity through hormonal dysregulation, mounting evidence now suggests that stress experienced prior to or during gestation may also negatively impact the health of future offspring. Rodent models of gestational physiologic stress can induce neurologic and behavioral changes that persist for up to three generations, suggesting that stress signals can induce lasting epigenetic changes in the germline. Treatment with glucocorticoid stress hormones is sufficient to recapitulate the transgenerational changes seen in physiologic stress models. These hormones are known to bind and activate the glucocorticoid receptor (GR), a ligand-inducible transcription factor, thus implicating GR-mediated signaling as a potential contributor to the transgenerational inheritance of stress-induced phenotypes. Here we demonstrate dynamic spatiotemporal regulation of GR expression in the mouse germline, showing expression in the fetal oocyte as well as the perinatal and adult spermatogonia. Functionally, we find that fetal oocytes are intrinsically buffered against changes in GR signaling, as neither genetic deletion of GR nor GR agonism with dexamethasone altered the transcriptional landscape or the progression of fetal oocytes through meiosis. In contrast, our studies revealed that the male germline is susceptible to glucocorticoid-mediated signaling, specifically by regulating RNA splicing within the spermatogonia, although this does not abrogate fertility. Together, our work suggests a sexually dimorphic function for GR in the germline, and represents an important step towards understanding the mechanisms by which stress can modulate the transmission of genetic information through the germline.

MkcDBGAS: a reference-free approach to identify comprehensive alternative splicing events in a transcriptome

Alternative splicing (AS) is an essential post-transcriptional mechanism that regulates many biological processes. However, identifying comprehensive types of AS events without guidance from a reference genome is still a challenge. Here, we proposed a novel method, MkcDBGAS, to identify all seven types of AS events using transcriptome alone, without a reference genome. MkcDBGAS, modeled by full-length transcripts of human and Arabidopsis thaliana, consists of three modules. In the first module, MkcDBGAS, for the first time, uses a colored de Bruijn graph with dynamic- and mixed- kmers to identify bubbles generated by AS with precision higher than 98.17% and detect AS types overlooked by other tools. In the second module, to further classify types of AS, MkcDBGAS added the motifs of exons to construct the feature matrix followed by the XGBoost-based classifier with the accuracy of classification greater than 93.40%, which outperformed other widely used machine learning models and the state-of-the-art methods. Highly scalable, MkcDBGAS performed well when applied to Iso-Seq data of Amborella and transcriptome of mouse. In the third module, MkcDBGAS provides the analysis of differential splicing across multiple biological conditions when RNA-sequencing data is available. MkcDBGAS is the first accurate and scalable method for detecting all seven types of AS events using the transcriptome alone, which will greatly empower the studies of AS in a wider field.

Profound Effects of Dexamethasone on the Immunological State, Synthesis and Secretion Capacity of Human Testicular Peritubular Cells

The functions of human testicular peritubular cells (HTPCs), forming a small compartment located between the seminiferous epithelium and the interstitial areas of the testis, are not fully known but go beyond intratesticular sperm transport and include immunological roles. The expression of the glucocorticoid receptor (GR) indicates that they may be regulated by glucocorticoids (GCs). Herein, we studied the consequences of the GC dexamethasone (Dex) in cultured HTPCs, which serves as a unique window into the human testis. We examined changes in cytokines, mainly by qPCR and ELISA. A holistic mass-spectrometry-based proteome analysis of cellular and secreted proteins was also performed. Dex, used in a therapeutic concentration, decreased the transcript level of proinflammatory cytokines, e.g., IL6, IL8 and MCP1. An siRNA-mediated knockdown of GR reduced the actions on IL6. Changes in IL6 were confirmed by ELISA measurements. Of note, Dex also lowered GR levels. The proteomic results revealed strong responses after 24 h (31 significantly altered cellular proteins) and more pronounced ones after 72 h of Dex exposure (30 less abundant and 42 more abundant cellular proteins). Dex also altered the composition of the secretome (33 proteins decreased, 13 increased) after 72 h. Among the regulated proteins were extracellular matrix (ECM) and basement membrane components (e.g., FBLN2, COL1A2 and COL3A1), as well as PTX3 and StAR. These results pinpoint novel, profound effects of Dex in HTPCs. If transferrable to the human testis, changes specifically in ECM and the immunological state of the testis may occur in men upon treatment with Dex for medical reasons.

Distinct Patterns of GR Transcriptional Regulation in Liver and Muscle of LPS-Challenged Weaning Piglets

Glucocorticoid receptor (GR), which is ubiquitously expressed in nearly all cell types of various organs, mediates the tissue-specific metabolic and immune responses to maintain homeostasis and ensure survival under stressful conditions or pathological challenges. The neonatal period is metabolically demanding, and piglets are subjected to multiple stressors in modern intensive farms, especially around weaning. The liver is more responsive to LPS challenge compared to muscle, which is indicated by significantly increased TLR4 and p-p65, TNF-α, and IL-6 levels in association with GR down-regulation at both mRNA and protein levels. GR binding to the putative nGRE on TNF-α and IL-6 gene promoters decreased in the liver, but not muscle, upon LPS stimulation. The transcriptional regulation of GR also showed striking differences between liver and muscle. GR exon 1 mRNA variants 1–4, 1–5, and 1–6 were down-regulated in both liver and muscle, but a significant up-regulation of GR exon 1–9/10 mRNA variants abolished the change of total GR mRNA in the muscle in response to LPS stimulation. The significant down-regulation of GR in the liver corresponded with significantly decreased binding of p-GR and diminished histone acetylation in GR gene promoters. These results indicate that tissue-specific GR transcriptional regulation is involved in the differential inflammation responses between liver and muscle.

Antenatal Steroids and Cord Blood T-cell Glucocorticoid Receptor DNA Methylation and Exon 1 Splicing

Antenatal administration of glucocorticoids such as betamethasone (BMZ) during the late preterm period improves neonatal respiratory outcomes. However, glucocorticoids may elicit programming effects on immune function and gene regulation. Here, we test the hypothesis that exposure to antenatal BMZ alters cord blood immune cell composition in association with altered DNA methylation and alternatively expressed Exon 1 transcripts of the glucocorticoid receptor (GR) gene in cord blood CD4⁺ T-cells. Cord blood was collected from 51 subjects in the Antenatal Late Preterm Steroids Trial: 27 BMZ, 24 placebo. Proportions of leukocytes were compared between BMZ and placebo. In CD4+ T-cells, methylation at CpG sites in the GR promoter regions and expression of GR mRNA exon 1 variants were compared between BMZ and placebo. BMZ was associated with an increase in granulocytes (51.6% vs. 44.7% p = 0.03) and a decrease in lymphocytes (36.8% vs. 43.0% p = 0.04) as a percent of the leukocyte population vs. placebo. Neither GR methylation nor exon 1 transcript levels differed between groups. BMZ is associated with altered cord blood leukocyte proportions, although no associated alterations in GR methylation were observed.

Molecular Signaling and Transcriptional Regulation of Histamine H1 Receptor Gene

Histamine-activated histamine H₁ receptor (H1R) signaling regulates many gene expressions, mainly through the protein kinase C (PKC)/extracellular signal-regulated kinases (ERK) signaling. Involvement of other signaling, including NF-κB, Wnt, RUNX-2, and Rho A signaling was also demonstrated. In addition, cAMP production through the activation of H1R signaling was reported. H1R gene itself is also up-regulated by the activation of H1R signaling with histamine. Here, we review our recent findings in the molecular signaling and transcriptional regulation of the H1R gene. Stimulation with histamine up-regulates H1R gene expression through the activation of H1R in HeLa cells. The PKCδ/ERK/poly(ADP)ribosyl transferase-1 (PARP-1) signaling was involved in this up-regulation. Heat shock protein 90 also plays an important role in regulating PKCδ translocation. Promoter analyses revealed the existence of two promoters in the human H1R gene in HeLa cells. H1R-activated H1R gene up-regulation in response to histamine was also observed in U373 astroglioma cells. However, this up-regulation was mediated not through the PKCδ signaling but possibly through the PKCα signaling. In addition, the promoter region responsible for histamine-induced H1R gene transcription in U373 cells was different from that of HeLa cells. These findings suggest that the molecular signaling and transcriptional regulation of the H1R gene are different between neuronal cells and non-neuronal cells.

Signaling Pathway of Histamine H1 Receptor-Mediated Histamine H1 Receptor Gene Upregulation Induced by Histamine in U-373 MG Cells

Histamine H₁ receptor (H1R) is one of the targets of histamine in the nervous system and the peripheral tissues. Protein kinase Cδ (PKCδ) signaling is involved in histamine-induced upregulation of H1R gene expression in HeLa cells. Histamine also upregulates H1R gene expression in U-373 MG cells. However, the molecular signaling of this upregulation is still unclear. Here, we investigated the molecular mechanism of histamine-induced H1R gene upregulation in U-373 MG cells. Histamine-induced H1R gene upregulation was inhibited by H1R antagonist d-chlorpheniramine, but not by ranitidine, ciproxifan, or JNJ77777120, and H2R, H3R, or H4R antagonists, respectively. Ro-31-8220 and Go6976 also suppressed this upregulation, however, the PKCδ selective inhibitor rottlerin and the PKCβ selective inhibitor Ly333531 did not. Time-course studies showed distinct kinetics of H1R gene upregulation in U-373 MG cells from that in HeLa cells. A promoter assay revealed that the promoter region responsible for H1R gene upregulation in U-373 MG cells was different from that of HeLa cells. These data suggest that the H1R-activated H1R gene expression signaling pathway in U-373 MG cells is different from that in HeLa cells, possibly by using different promoters. The involvement of PKCα also suggests that compounds that target PKCδ could work as peripheral type H1R-selective inhibitors without a sedative effect.

Genome-wide methylation in alcohol use disorder subjects: implications for an epigenetic regulation of the cortico-limbic glucocorticoid receptors (NR3C1)

Environmental factors, including substance abuse and stress, cause long-lasting changes in the regulation of gene expression in the brain via epigenetic mechanisms, such as DNA methylation. We examined genome-wide DNA methylation patterns in the prefrontal cortex (PFC, BA10) of 25 pairs of control and individuals with alcohol use disorder (AUD), using the Infinium^® MethylationEPIC BeadChip. We identified 5254 differentially methylated CpGs (p_nominal < 0.005). Bioinformatic analyses highlighted biological processes containing genes related to stress adaptation, including the glucocorticoid receptor (encoded by NR3C1). Considering that alcohol is a stressor, we focused our attention on differentially methylated regions of the NR3C1 gene and validated the differential methylation of several genes in the NR3C1 network. Chronic alcohol drinking results in a significant increased methylation of the NR3C1 exon variant 1_H, with a particular increase in the levels of 5-hydroxymethylcytosine over 5-methylcytosine. These changes in DNA methylation were associated with reduced NR3C1 mRNA and protein expression levels in PFC, as well as other cortico-limbic regions of AUD subjects when compared with controls. Furthermore, we show that the expression of several stress-responsive genes (e.g., CRF, POMC, and FKBP5) is altered in the PFC of AUD subjects. These stress-response genes were also changed in the hippocampus, a region that is highly susceptible to stress. These data suggest that alcohol-dependent aberrant DNA methylation of NR3C1 and consequent changes in other stress-related genes might be fundamental in the pathophysiology of AUD and lay the groundwork for treatments targeting the epigenetic mechanisms regulating NR3C1 in AUD.

Fetal programming in dairy cows: Effect of heat stress on progeny fertility and associations with the hypothalamic-pituitary-adrenal axis functions

Ambient temperatures that result in body temperatures beyond those of the thermo-neutral zone for dairy cattle can lead to reduced reproductive efficiencies that have negative effects on economic and productive efficiencies of dairy farms. In addition, in pregnant cows, ambient temperature-induced heat stress leads to modifications in the epigenome of the developing embryo, which, in turn, could lead to phenotypic variations in the sexually mature animal and its offspring. In the mammalian response to stress, adrenocorticotropic hormone stimulates the synthesis and secretion of glucocorticoids, which may have detrimental effects on the hypothalamic-pituitary-gonadal axis and the female estrous cycle. The aim of this review is to describe the effects of ambient heat stress on the reproductive system of dairy cattle and its potential trans-generational effects. There are many heat stress occurrences in dairy cattle during a large portion of the year in many countries and there is an increase in incidence with the onset of global warming. These heat stress conditions make it possible that the embryo/fetus of cows may be affected when heat stress conditions prevail in ways that there is impaired fertility of the sexually mature cows that develop from these embryos/fetuses. This is the outcome because of molecular changes in ovarian glucocorticoid response caused by epigenetic modifications established during fetal development.

Altered Expression of Glucocorticoid Receptor and Neuron-Specific Enolase mRNA in Peripheral Blood in First-Episode Schizophrenia and Chronic Schizophrenia

INTRODUCTION

It is well-known that altered hypothalamus-pituitary-adrenal (HPA) axis process has an important role in the neurodegenerative process in schizophrenia (SZ). However, this neurodegenerative mechanism has not been clarified in SZ. Therefore, the main purpose of this study was to determine HPA axis damage in the first-episode, unmedicated schizophrenia (FES) patients and chronic schizophrenia (CSZ) patients in comparison with healthy controls (HC) by means of quantitative analysis of the peripheral blood mRNA expression of glucocorticoid receptor (GR), GR transcripts containing exons 1B (GR-1B), and neuron specific enolase (NSE) genes and serum cortisol and NSE, a specific serum marker for neuronal damage.

METHODS

In the present study, 43 FES patients, 39 CSZ, and 47 HC were included. The peripheral blood mRNA expressions for GR, GR-1B, and NSE genes were determined by real-time quantitative polymerase chain reaction (RT-qPCR). Serum cortisol and NSE were analyzed by electrochemiluminescence immunoassay technique.

RESULTS

Levels of GR mRNA were significantly lower in FES and CSZ than that in HC. The expression of GR-1B mRNA was significantly decreased in CSZ when compared with that in FES. Levels of NSE mRNA were significantly lower in CSZ than that in FES patients or HC patients. CSZ patients showed significantly lower cortisol concentrations than FES and HC patients. FES patients showed significantly higher NSE concentrations than CSZ and HC.

CONCLUSION

Our findings support that there is disrupted HPA axis system in the SZ and suggest that CSZ patients suffer a greater HPA axis damage than FES patients. Our research implicated underlying GR mRNA dysregulation in SZ and the potential importance of the functional GR-1B transcription in CSZ.

Alternatively spliced isoforms reveal a novel type of PTB domain in CCM2 protein

Cerebral cavernous malformations (CCMs) is a microvascular disorder in the central nervous system. Despite tremendous efforts, the causal genetic mutation in some CCM patients has not be identified, raising the possibility of an unknown CCM locus. The CCM2/MGC4607 gene has been identified as one of three known genes causing CCMs. In this report, we defined a total of 29 novel exons and 4 novel promoters in CCM2 genomic structure and subsequently identified a total of 50 new alternative spliced isoforms of CCM2 which eventually generated 22 novel protein isoforms. Genetic analysis of CCM2 isoforms revealed that the CCM2 isoforms can be classified into two groups based on their alternative promoters and alternative start codon exons. Our data demonstrated that CCM2 isoforms not only are specific in their subcellular compartmentation but also have distinct cellular expression patterns among various tissues and cells, indicating the pleiotropic cellular roles of CCM2 through their multiple isoforms. In fact, the complexity of the CCM2 genomic structure was reflected by the multiple layers of regulation of CCM2 expression patterns. At the transcriptional level, it is accomplished by alternative promoters, alternative splicing, and multiple transcriptional start sites and termination sites; while at the translational level, it is carried out with various cellular functions with a distinguishable CCM2 protein group pattern, specified abundance and composition of selective isoforms in a cell and tissue specific fashion. Through experimentation, we discovered a unique phosphotyrosine binding (PTB) domain, namely atypical phosphotyrosine binding (aPTB) domain. Some long CCM2 isoform proteins contain both classes of PTB domains, making them a dual PTB domain-containing protein. Both CCM1 and CCM3 can bind competitively to this aPTB domain, indicating CCM2 as the cornerstone for CCM signaling complex (CSC).

Parent and offspring genotypes influence gene expression in early life

Parents can have profound effects on offspring fitness. Little, however, is known about the mechanisms through which parental genetic variation influences offspring physiology in natural systems. White-throated sparrows (Zonotrichia albicollis, WTSP) exist in two genetic morphs, tan and white, controlled by a large polymorphic supergene. Morphs mate disassortatively, resulting in two pair types: tan male × white female (T × W) pairs, which provide biparental care and white male × tan female (W × T) pairs, which provide female-biased care. To investigate how parental composition impacts offspring, we performed RNA-seq on whole blood of WTSP nestlings sampled from nests of both pair types. Parental pair type had a large effect on nestling gene expression, with 881 genes differentially expressed (DE) and seven correlated gene coexpression modules. The DE genes and modules expressed at higher levels in W × T nests with female-biased parental care function in metabolism and stress-related pathways resulting from the overrepresentation of proteolysis and stress-response genes (e.g., SOD2, NR3C1). These results show that parental genotypes and/or associated behaviours influence nestling physiology, and highlight avenues of further research investigating the ultimate implications for the maintenance of this polymorphism. Nestlings also exhibited morph-specific gene expression, with 92 differentially expressed genes, comprising immunity genes and genes encompassed by the supergene. Remarkably, we identified the same regulatory hub genes in these blood-derived expression networks as were previously identified in adult WTSP brains (EPM2A, BPNT1, TAF5L). These hub genes were located within the supergene, highlighting the importance of this gene complex in structuring regulatory networks across diverse tissues.

Antenatal Hypoxia and Programming of Glucocorticoid Receptor Expression in the Adult Rat Heart

Glucocorticoid receptor (GR) signaling is critical for development and function of the heart. Our previous study demonstrated that gestational hypoxia induced epigenetic repression of the GR gene in the developing heart. The present study aims to determine that the alterations of promoter methylation level and epigenetic repression of the GR gene in the developing heart in response to maternal hypoxia is sustained in adult offspring and potential gender differences in the programming of GR gene. Pregnant rats were treated with 10.5% O₂ from gestational day 15 (E15) to 21 (E21). Hearts were isolated from 5-month-old male and female offspring with the developing stage being equivalent to 18-year-old human. GR mRNA and protein abundance was determined with real time qRT-PCR and Western blot. GR gene promoter methylation and binding of transcription factors were measured with methylated DNA immunoprecipitation (MeDIP) and Chromatin immunoprecipitation (ChIP). The results showed that antenatal hypoxia significantly decreased the expression of GR mRNA and protein in the hearts of adult male offspring, but not in females, which is ascribed to the differential changes of alternative exon1 mRNA variants of GR gene in male and female hearts in response to prenatal hypoxia. In addition, the downregulation of GR expression in the male heart was correlated with increased methylation levels of CpG dinucleotides in promoters of exon 1₄, 1₅, 1₆, 1₇, and 1₁₀, which resulted in a decrease in the binding of their transcription factors. Thus, the study reveals that antenatal hypoxia results in a reprogramming and long-term change in GR gene expression in the heart by hypermethylation of GR promoter in a sex-differential pattern, which provides a novel mechanism regarding the increased vulnerability of heart later in life with exposure of prenatal hypoxia.

Saponins as modulators of nuclear receptors

As plant-derived natural products, saponins have been widely applied for the dietary modification of metabolic syndrome. However, the underlying mechanisms of their preventive and therapeutic effects are still largely unclear. Nuclear receptors have been identified as potential pharmaceutical targets for treating various types of metabolic disorders. With similar structure to endogenous hormones, several saponins may serve as selective ligands for nuclear receptors. Recently, a series of saponins are proved to exert their physiological activities through binding to nuclear receptors. This review summarizes the biological and pharmacological activities of typical saponins mediated by some of the most well described nuclear receptors, including the classical steroid hormone receptors (ER, GR, MR, and AR) and the adopted orphan receptors (PPAR, LXR, FXR, and PXR).

Corticosteroid Receptors in the Brain: Transcriptional Mechanisms for Specificity and Context-Dependent Effects

Corticosteroid hormones act in the brain to support adaptation to stress via binding to mineralocorticoid and glucocorticoid receptors (MR and GR). These receptors act in large measure as transcription factors. Corticosteroid effects can be highly divergent, depending on the receptor type, but also on brain region, cell type, and physiological context. These differences ultimately depend on differential interactions of MR and GR with other proteins, which determine ligand binding, nuclear translocation, and transcriptional activities. In this review, we discuss established and potential mechanisms that confer receptor and cell type-specific effects of the MR and GR-mediated transcriptional effects in the brain.

Epigenetic Programming by Maternal Behavior in the Human Infant

: media-1vid110.1542/5804912859001PEDS-VA_2017-1890Video Abstract OBJECTIVES: We sought to determine if variations in maternal care alter DNA methylation in term, healthy, 5-month-old infants. This work was based on landmark studies in animal models demonstrating that nurturing care by dams would alter their newborns' stress responses through epigenetic mechanisms. We used breastfeeding as a proxy for animal maternal behavior. We hypothesized alterations in DNA methylation of the glucocorticoid receptor gene and less hypothalamic stress response in infants of mothers who breastfed their infants versus infants of mothers who did not breastfeed.

METHODS

A cohort study of term, healthy infants and their mothers who did (n = 21) or did not (n = 21) breastfeed for the first 5 months was used in this analysis. Cortisol stress reactivity was measured in infant saliva by using a mother-infant interaction procedure and DNA methylation of an important regulatory region of the glucocorticoid receptor gene. Changes in DNA methylation of this gene in humans were compared to homologous regions of the rat gene. DNA samples were prepared from cheek swabs and subjected to quantitative analysis of the extent of methylation by using sensitive sequencing techniques.

RESULTS

Breastfeeding was associated with decreased DNA methylation of the glucocorticoid receptor promoter and decreased cortisol reactivity in 5-month-old infants. Decreased DNA methylation occurred in the promoter region involved in regulation of the hypothalamic-pituitary-adrenal and immune system responses.

CONCLUSIONS

Maternal care in humans may impact the hypothalamic-pituitary-adrenal stress response through behavioral programming and manifest as offspring epigenetic change. These results explain, in part, some of the positive effects observed in children who are breastfed.

Pharmacogenomic markers of glucocorticoid response in the initial phase of remission induction therapy in childhood acute lymphoblastic leukemia

Background

Response to glucocorticoid (GC) monotherapy in the initial phase of remission induction treatment in childhood acute lymphoblastic leukemia (ALL) represents important biomarker of prognosis and outcome. We aimed to study variants in several pharmacogenes (NR3C1, GSTs and ABCB1) that could contribute to improvement of GC response through personalization of GC therapy.

Methods

Retrospective study enrolling 122 ALL patients was carried out to analyze variants of NR3C1 (rs33389, rs33388 and rs6198), GSTT1 (null genotype), GSTM1 (null genotype), GSTP1 (rs1695 and rs1138272) and ABCB1 (rs1128503, rs2032582 and rs1045642) genes using PCR-based methodology. The marker of GC response was blast count per microliter of peripheral blood on treatment day 8. We carried out analysis in which cut-off value for GC response was 1000 (according to Berlin-Frankfurt-Munster [BFM] protocol), as well as 100 or 0 blasts per microliter.

Results

Carriers of rare NR3C1 rs6198 GG genotype were more likely to have blast count over 1000, than the non-carriers (p = 0.030). NR3C1 CAA (rs33389-rs33388-rs6198) haplotype was associated with blast number below 1000 (p = 0.030). GSTP1 GC haplotype carriers were more likely to have blast number below 1000 (p = 0.036), below 100 (p = 0.028) and to be blast negative (p = 0.054), while GSTP1 GT haplotype and rs1138272 T allele carriers were more likely to be blasts positive (p = 0.034 and p = 0.024, respectively). ABCB1 CGT (rs1128503-rs2032582-rs1045642) haplotype carriers were more likely to be blast positive (p = 0.018).

Conclusions

Our results have shown that NR3C1 rs6198 variant and GSTP1 rs1695-rs1138272 haplotype are the most promising pharmacogenomic markers of GC response in ALL patients.

A Functional Mutation in KIAA1462 Promoter Decreases Glucocorticoid Receptor Affinity and Affects Egg-Laying Performance in Yangzhou Geese

The identification of genetic markers is valuable for improving the egg-laying performance in goose production. The single-nucleotide polymorphism (SNP) rs1714766362 in an intron of the goose KIAA1462 gene was found to be relevant to laying performance in our previous study. However, its function remains unclear. In this study, the full-length coding sequence of KIAA1462 gene was firstly characterized in Yangzhou geese. Q-PCR (Quantitative Real Time Polymerase Chain Reaction) results showed that KIAA1462 was highly expressed in the liver, ovary, and mature F1 follicles. For SNP rs1714766362, geese with the AA genotype showed better laying performance than the TT ones and exhibited a higher KIAA1462 expression level in the ovary. Gain- and loss-of function experiments in granulosa cells revealed that KIAA1462 affected the expression of the apoptosis marker gene caspase-3. Considering that rs1714766362 locates in an intron area, we compared the KIAA1462 promoter regions of AA and TT individuals and identified the SNP c.-413C>G (Genbank ss2137504176), which was completely linked to SNP rs1714766362. According to the transcription factor prediction results, the glucocorticoid receptor (GR) would bind to the SNP site containing the C but not the G allele. In this study, we proved this hypothesis by an electrophoretic mobility shift assay (EMSA). In summary, we identified a novel mutation in the promoter of KIAA1462 gene which can modulate GR binding affinity and affect the laying performance of geese.

Epigenetic mechanisms in the placenta related to infant neurodevelopment

As the 'third brain' the placenta links the developing fetal brain and the maternal brain enabling study of epigenetic process in placental genes that affect infant neurodevelopment. We described the characteristics and findings of the 17 studies on epigenetic processes in placental genes and human infant neurobehavior. Studies showed consistent findings in the same cohort of term healthy infants across epigenetic processes (DNA methylation, genome wide, gene and miRNA expression) genomic region (single and multiple genes, imprinted genes and miRNAs) using candidate gene and genome wide approaches and across biobehavioral systems (neurobehavior, cry acoustics and neuroendocrine). Despite limitations, studies support future work on molecular processes in placental genes related to neurodevelopmental trajectories including implications for intervention.

MicroRNA-210 suppresses glucocorticoid receptor expression in response to hypoxia in fetal rat cardiomyocytes

Hypoxia is a common intrauterine stressor, often resulting in intrauterine growth restriction and increased risk for cardiovascular disease later in life. The aim of this work was to test the hypothesis that microRNA-210 (miR-210) mediates the detrimental suppression of glucocorticoid receptor (GR) in response to hypoxia in fetal rat cardiomyocytes. Cardiomyocytes isolated from gestational day 21 Sprague Dawley fetal rats showed increased miR-210 levels and reduced GR abundance after exposure to ex vivo hypoxia (1% O2). In regard to mechanisms, the different contributions of hypoxia response elements (HREs) motifs in the regulation of miR-210 promoter activity and the miR-210-mediated repression of GR expression were determined in rat embryonic heart-derived myogenic cell line H9c2. Moreover, using a cell culture-based model of hypoxia-reoxygenation injury, we assessed the cytotoxic effects of GR suppression under hypoxic conditions. The results showed that hypoxia induced HIF-1α-dependent miR-210 production, as well as miR-210-mediated GR suppression, in cardiomyocytes. Furthermore, inhibition or knockdown of GR exacerbated cell death in response to hypoxia-reoxygenation injury. Altogether, the present study demonstrates that the HIF-1α-dependent miR-210-mediated suppression of GR in fetal rat cardiomyocytes increases cell death in response to hypoxia, providing novel evidence for a possible mechanistic link between fetal hypoxia and programming of ischemic-sensitive phenotype in the developing heart.

DNA methylation: conducting the orchestra from exposure to phenotype?

DNA methylation, through 5-methyl- and 5-hydroxymethylcytosine (5mC and 5hmC), is considered to be one of the principal interfaces between the genome and our environment, and it helps explain phenotypic variations in human populations. Initial reports of large differences in methylation level in genomic regulatory regions, coupled with clear gene expression data in both imprinted genes and malignant diseases, provided easily dissected molecular mechanisms for switching genes on or off. However, a more subtle process is becoming evident, where small (<10 %) changes to intermediate methylation levels are associated with complex disease phenotypes. This has resulted in two clear methylation paradigms. The latter “subtle change” paradigm is rapidly becoming the epigenetic hallmark of complex disease phenotypes, although we are currently hampered by a lack of data addressing the true biological significance and meaning of these small differences.

Our initial expectation of rapidly identifying mechanisms linking environmental exposure to a disease phenotype led to numerous observational/association studies being performed. Although this expectation remains unmet, there is now a growing body of literature on specific genes, suggesting wide ranging transcriptional and translational consequences of such subtle methylation changes. Data from the glucocorticoid receptor (NR3C1) has shown that a complex interplay between DNA methylation, extensive 5′UTR splicing, and microvariability gives rise to the overall level and relative distribution of total and N-terminal protein isoforms generated. Additionally, the presence of multiple AUG translation initiation codons throughout the complete, processed mRNA enables translation variability, hereby enhancing the translational isoforms and the resulting protein isoform diversity, providing a clear link between small changes in DNA methylation and significant changes in protein isoforms and cellular locations. Methylation changes in the NR3C1 CpG island alters the NR3C1 transcription and eventually protein isoforms in the tissues, resulting in subtle but visible physiological variability.

This review addresses the current pathophysiological and clinical associations of such characteristically small DNA methylation changes, the ever-growing roles of DNA methylation and the evidence available, particularly from the glucocorticoid receptor of the cascade of events initiated by such subtle methylation changes, as well as addressing the underlying question as to what represents a genuine biologically significant difference in methylation.

Where does transcription start? 5'-RACE adapted to next-generation sequencing

The variability and complexity of the transcription initiation process was examined by adapting RNA ligase-mediated rapid amplification of 5' cDNA ends (5'-RACE) to Next-Generation Sequencing (NGS). We oligo-labelled 5'-m(7)G-capped mRNA from two genes, the simple mono-exonic Beta-2-Adrenoceptor (ADRB2R)and the complex multi-exonic Glucocorticoid Receptor (GR, NR3C1), and detected a variability in TSS location that has received little attention up to now. Transcription was not initiated at a fixed TSS, but from loci of 4 to 10 adjacent nucleotides. Individual TSSs had frequencies from <0.001% to 38.5% of the total gene-specific 5' m(7)G-capped transcripts. ADRB2R used a single locus consisting of 4 adjacent TSSs. Unstimulated, the GR used a total of 358 TSSs distributed throughout 38 loci, that were principally in the 5' UTRs and were spliced using established donor and acceptor sites. Complete demethylation of the epigenetically sensitive GR promoter with 5-azacytidine induced one new locus and 127 TSSs, 12 of which were unique. We induced GR transcription with dexamethasone and Interferon-γ, adding one new locus and 185 additional TSSs distributed throughout the promoter region. In-vitro the TSS microvariability regulated mRNA translation efficiency and the relative abundance of the different GRN-terminal protein isoform levels.

Epigenetics/Programming in the HPA Axis

The hypothalamic-pituitary-adrenal axis provides physiological adaptations to various environmental stimuli in mammals. These stimuli including maternal care, diet, immune challenge, stress, and others have the potential to stably modify or program the functioning of the HPA axis when experienced early in life or at later critical stages of development. Epigenetic mechanisms mediate the biological embedding of environmental stimuli or conditions. These changes are influenced by the genotype and both, environment and genotype contribute to the development of a specific phenotype with regard to the stress response that might be more susceptible or resilient to the development of mental conditions. The effects of stress might be a result of cumulative stress or a mismatch between the environments experienced early in life versus the conditions much later. These effects including the associated epigenetic modifications are potentially reversible.

Early life trauma, depression and the glucocorticoid receptor gene--an epigenetic perspective

BACKGROUND

Hopes to identify genetic susceptibility loci accounting for the heritability seen in unipolar depression have not been fully realized. Family history remains the 'gold standard' for both risk stratification and prognosis in complex phenotypes such as depression. Meanwhile, the physiological mechanisms underlying life-event triggers for depression remain opaque. Epigenetics, comprising heritable changes in gene expression other than alterations of the nucleotide sequence, may offer a way to deepen our understanding of the aetiology and pathophysiology of unipolar depression and optimize treatments. A heuristic target for exploring the relevance of epigenetic changes in unipolar depression is the hypothalamic-pituitary-adrenal (HPA) axis. The glucocorticoid receptor (GR) gene (NR3C1) has been found to be susceptible to epigenetic modification, specifically DNA methylation, in the context of environmental stress such as early life trauma, which is an established risk for depression later in life.

METHOD

In this paper we discuss the progress that has been made by studies that have investigated the relationship between depression, early trauma, the HPA axis and the NR3C1 gene. Difficulties with the design of these studies are also explored.

RESULTS

Future efforts will need to comprehensively address epigenetic natural histories at the population, tissue, cell and gene levels. The complex interactions between the epigenome, genome and environment, as well as ongoing nosological difficulties, also pose significant challenges.

CONCLUSIONS

The work that has been done so far is nevertheless encouraging and suggests potential mechanistic and biomarker roles for differential DNA methylation patterns in NR3C1 as well as novel therapeutic targets.

Endothelial glucocorticoid receptor promoter methylation according to dexamethasone sensitivity

We have previously shown that in vitro sensitivity to dexamethasone (DEX) stimulation in human endothelial cells is positively regulated by the glucocorticoid receptor (NR3C1, GR). The present study determined the role of differential GR transcriptional regulation in glucocorticoid sensitivity. We studied 25 human umbilical vein endothelial cells (HUVECs) that had been previously characterized as DEX-sensitive (n=15), or resistant (n=10). Real-time PCR analysis of GR 5'UTR mRNA isoforms showed that all HUVECs expressed isoforms 1B, 1C, 1D, 1F, and 1H, and isoforms 1B and 1C were predominantly expressed. DEX-resistant cells expressed higher basal levels of the 5'UTR mRNA isoforms 1C and 1D, but lower levels of the 5'UTR mRNA isoform 1F than DEX-sensitive cells. DEX treatment significantly decreased GRα and GR-1C mRNA isoform expression in DEX-resistant cells only. Reporter luciferase assays indicated that differential GR mRNA isoform expression was not due to differential promoter usage between DEX-sensitive and DEX-resistant cells. Analysis of promoter methylation, however, showed that DEX-sensitive cells have higher methylation levels of promoter 1D and lower methylation levels of promoter 1F than DEX-resistant cells. Treatment with 5-aza-2-deoxycytidine abolished the differential 5'UTR mRNA isoform expression between DEX-sensitive and DEX-resistant cells. Finally, both GRα overexpression and 5-aza-2-deoxycytidine treatment eliminated the differences between sensitivity groups to DEX-mediated downregulation of endothelial nitric oxide synthase (NOS3), and upregulation of plasminogen activator inhibitor 1 (SERPINE1). In sum, human endothelial GR 5'UTR mRNA expression is regulated by promoter methylation with DEX-sensitive and DEX-resistant cells having different GR promoter methylation patterns.

Breed-specific expression of GR exon 1 mRNA variants and profile of GR promoter CpG methylation in the hippocampus of newborn piglets

Glucocorticoid receptor (GR) transcription is driven by alternative promoters to produce different exon 1 mRNA variants. CpG methylation on GR promoters profoundly affects GR transcription. GR in hippocampus is critical for energy homeostasis and stress responses, yet it remains unclear whether hippocampal expression of GR exon 1 mRNA variants and the methylation status of GR promoters differ between Large White (LW) and Erhualian (EHL) pigs showing distinct metabolic and stress-coping characteristics. EHL pigs had higher hippocampus weight relative to BW (P<0.01), which was associated with higher serum cortisol level compared with LW pigs. Hippocampal expression of brain-derived neurotrophic factor (P<0.05) was significantly higher, while Bax, a pro-apoptotic gene, was significantly lower in EHL pigs (P<0.05). Hippocampal expression of total GR did not differ between breeds, yet GR exon 1 to 11 mRNA was significantly higher (P<0.01) in EHL pigs, which was associated with a trend of increase (P=0.057) in GR protein content. No significant breed difference was detected for the methylation status across the whole region of the proximal GR promoter, while CpG334 and CpG266.267 were differentially methylated, in a reversed manner, between breeds. The methylation status of CpGs 248, 259, 260, 268 and 271 was negatively correlated (P<0.05) with GR exon 1 to 11 mRNA abundance. Our results provide fundamental information on the breed-specific characteristics of GR and its mRNA variants expression and the status of DNA methylation on the proximal GR promoter in the pig hippocampus.

Corticosteroid use in neuro-oncology: an update

Because of the lack of curative approaches for most patients with malignant brain tumors, supportive therapy, which aims at maintaining quality of life and functional independence, has a central role in the treatment of many patients. Steroids are particularly important in the setting of supportive therapy. They are commonly used to treat tumor-associated edema, and their administration is typically associated with rapid symptom relief, such as the resolution of headaches. Besides their antiedema activity, corticosteroids are characterized by their potent antilymphoma properties and their effects against acute or delayed emesis caused by systemic chemotherapy in cancer patients. Accordingly, steroids are among the most frequently used drugs in oncology. These desirable properties of steroids are counterbalanced by cardiovascular, muscular, and psychiatric side effects. On the cellular level, corticosteroids exert various effects that translate into the desired clinical activity, but they also evoke significant toxicity that may outweigh the beneficial effects. The mode of action and the limitations of steroid treatment are summarized in this review article. Interactions between steroids and other drugs must be considered. A particular challenge to the ongoing use of glucocorticoids is that newer therapeutic approaches are being introduced in neuro-oncology for which concomitant steroids are likely to be contraindicated. These include the emergence of various immunotherapeutic approaches including vaccination strategies and treatment with immune checkpoint inhibitors. Since the administration of steroids may interfere with the activity of these novel therapies, an even more critical evaluation of their use will be required.

Mechanisms of glucocorticoid action and insensitivity in airways disease

Glucocorticoids are the mainstay for the treatment of chronic inflammatory diseases including asthma and chronic obstructive pulmonary disease (COPD). However, it has been recognized that glucocorticoids do not work well in certain patient populations suggesting reduced sensitivity. The ultimate biologic responses to glucocorticoids are determined by not only the concentration of glucocorticoids but also the differences between individuals in glucocorticoid sensitivity, which is influenced by multiple factors. Studies are emerging to understand these mechanisms in detail, which would help in increasing glucocorticoid sensitivity in patients with chronic airways disease. This review aims to highlight both classical and emerging concepts of the anti-inflammatory mechanisms of glucocorticoids and also review some novel strategies to overcome steroid insensitivity in airways disease.

Porcine glucocorticoid receptor (NR3C1) gene: tissue-specificity of transcriptional strength and glucocorticoid responsiveness of alternative promoters

Glucocorticoid receptor (GR) is transcribed in a tissue- and cell-specific manner with multiple exon 1 mRNA variants driven by selective promoters. We recently cloned and characterized the 5.3kb proximal promoter sequence of porcine GR gene containing 7 untranslated alternative first exons each processed by a distinct promoter. In this study, we showed tissue-specific expression of total GR and its exon 1 mRNA variants in hippocampus, muscle and liver of pigs. Total GR mRNA was most abundant in liver, followed by muscle and hippocampus in descending order. Among all the GR exon 1 mRNA variants detected, GR exon 1-9/10 and 1-4 were the most predominant variants in all the three tissues. The abundance of GR exon 1-4 mRNA was similar to that of 1-10 in muscle, but was significantly lower than 1-10 in liver and hippocampus. The activities of truncated short (S) and long (L) promoters of respective GR exon 1 mRNA variants were analyzed by luciferase reporter assay in 3 representative cell lines, SY5Y, C2C12 and HepG2. S1-10 and S1-4 demonstrated significantly higher activities than other short promoters in all the cell lines examined. Nevertheless, the strongest activity and cell specificity were detected for L1-10 promoter, which was consistent with the predominant exon 1-9/10 expression in porcine tissues. Moreover, with 3 potential nGRE binding sites, L1-10 promoter was more sensitive to dexamethasone (DEX) in HepG2. Our data provide basic knowledge of the transcriptional mechanism underlying the tissue- and cell-specific expression of porcine GR under basal or ligand-stimulated conditions.

Glucocorticoid receptor gene (NR3C1) methylation following stressful events between birth and adolescence. The TRAILS study

Stress early in life is a known risk factor for the development of affective disorders later in life. Epigenetic mechanisms, such as DNA methylation, may have an important role in mediating that risk. Recent epigenetic research reported on the long-term relationship between traumatic stress in childhood and DNA methylation in adulthood. In this study, we examined the impact of various types of stress (perinatal stress, stressful life events (SLEs) and traumatic youth experiences) on methylation of the glucocorticoid receptor gene (NR3C1) in the blood of a population sample of 468 adolescents (50.4% female, mean age 16.1 years). Second, we determined whether stress at different ages was associated with higher NR3C1 methylation. NR3C1 methylation rates were higher after exposure to SLEs and after exposure to traumatic youth experiences. NR3C1 methylation in adolescence was not higher after exposure to perinatal stress. Experience of SLEs in adolescence was associated with a higher NR3C1 methylation, independently of childhood SLEs. We demonstrate that not only traumatic youth experiences but also (more common) SLEs are associated with higher NR3C1 methylation. In addition, our findings underline the relevance of adolescent stress for epigenetic changes in the NR3C1 gene.

Fetal hypoxia increases vulnerability of hypoxic-ischemic brain injury in neonatal rats: role of glucocorticoid receptors

Gestational hypoxia is a common stress to the fetal development and increases the risk of neonatal morbidity. The present study tested the hypothesis that fetal hypoxia results in heightened brain vulnerability to hypoxic-ischemic (HI) injury in neonatal rats via down-regulation of glucocorticoid receptor (GR) in the developing brain. Time-dated pregnant rats were exposed to hypoxia (10.5% O2) from days 15 to 21 of gestation. Brain HI injury was determined in day 10 pups. Maternal hypoxia resulted in asymmetric intrauterine growth restriction in the fetus. The brain HI injury was significantly increased in maternal hypoxia-treated pups as compared with the normoxia control in both males and females. Activation of brain GR by dexamethasone injection into the right lateral ventricle produced a concentration-dependent reduction of HI-induced brain injury in control pups. Maternal hypoxia significantly decreased GR mRNA and protein abundance in the fetal brain and neonatal hippocampus and abolished the dexamethasone-mediated neuroprotective effect in pup brains. This decreased GR expression was resulted from increased DNA methylation, decreased binding of transcription factors Egr-1 and Sp1 to GR gene exon 17 and 111 promoters, and reduced expression of GR exon 17 and 111 mRNA variants. The results demonstrate that gestational hypoxia causes epigenetic repression of GR gene expression in the developing brain resulting in the heightened brain vulnerability to HI injury in neonatal rats.

Role of the hypothalamic-pituitary-adrenal axis in developmental programming of health and disease

Adverse environments during the fetal and neonatal development period may permanently program physiology and metabolism, and lead to increased risk of diseases in later life. Programming of the hypothalamic-pituitary-adrenal (HPA) axis is one of the key mechanisms that contribute to altered metabolism and response to stress. Programming of the HPA axis often involves epigenetic modification of the glucocorticoid receptor (GR) gene promoter, which influences tissue-specific GR expression patterns and response to stimuli. This review summarizes the current state of research on the HPA axis and programming of health and disease in the adult, focusing on the epigenetic regulation of GR gene expression patterns in response to fetal and neonatal stress. Aberrant GR gene expression patterns in the developing brain may have a significant negative impact on protection of the immature brain against hypoxic-ischemic encephalopathy in the critical period of development during and immediately after birth.

Decreased hippocampal mineralocorticoid:glucocorticoid receptor ratio is associated with low birth weight in female cynomolgus macaque neonates

During pregnancy, glucocorticoids transfer environmental signals to the growing brain and its associated neuroendocrine system to modulate their maturation and function during adolescence and adulthood. Increased in utero exposure to glucocorticoids is associated with impaired fetal growth resulting in low birth weight (LBW) and compromised neural development. The underlying molecular changes affecting brain development, however, are largely unknown. Here, we compared the relative mRNA expression of genes directly involved in glucocorticoid signaling in the hippocampus, amygdala, and cortex of female non-human primate neonates (Macaca fascicularis) of naturally occurring normal birth weight and LBW. We focused on the glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) genes as well as that for 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) and found a significantly decreased MR:GR mRNA ratio in the hippocampus and lower expression of 11β-HSD1 in the amygdala associated with LBW. The MR:GR mRNA ratio in the amygdala and cortex was not associated with birth weight, reflecting tissue-specific effects. Protein quantification in the hippocampus confirmed our finding of a decreased hippocampal MR:GR ratio. Our data suggest that the MR:GR ratio in the hippocampus and the expression of 11β-HSD1 in the amygdala are associated with intrauterine growth restriction in non-human primates during early perinatal development.

Glucocorticoid receptor mRNA and protein isoform alterations in the orbitofrontal cortex in schizophrenia and bipolar disorder

BACKGROUND

The orbitofrontal cortex (OFC) may play a role in the pathogenesis of psychiatric illnesses such as bipolar disorder and schizophrenia, in which hypothalamic-pituitary-adrenal (HPA) axis abnormalities are observed and stress has been implicated. A critical component of the HPA axis which mediates cellular stress responses in the OFC, and has been implicated in psychiatric illness, is the glucocorticoid receptor (GR).

METHODS

In the lateral OFC, we employed quantitative real-time PCR and western blotting to investigate GR mRNA and protein expression in 34 bipolar disorder cases, 35 schizophrenia cases and 35 controls. Genotype data for eleven GR gene (NR3C1) polymorphisms was also used to explore possible effects of NR3C1 sequence variation on GR mRNA and protein expression in the lateral OFC.

RESULTS

We found no diagnostic differences in pan GR, GR-1C or GR-1F mRNA expression. However, the GR-1B mRNA transcript variant was decreased (14.3%) in bipolar disorder cases relative to controls (p < 0.05), while GR-1H mRNA was decreased (22.0%) in schizophrenia cases relative to controls (p < 0.005). By western blotting, there were significant increases in abundance of a truncated GRα isoform, putative GRα-D1, in bipolar disorder (56.1%, p < 0.005) and schizophrenia (31.5% p < 0.05). Using genotype data for eleven NR3C1 polymorphisms, we found no evidence of effects of NR3C1 genotype on GR mRNA or GRα protein expression in the OFC.

CONCLUSIONS

These findings reveal selective abnormalities of GR mRNA expression in the lateral OFC in psychiatric illness, which are more specific and may be less influenced by NR3C1 genotype than those of the dorsolateral prefrontal cortex reported previously. Our results suggest that the GRα-D1 protein isoform may be up-regulated widely across the frontal cortex in psychiatric illness.

Breed-dependent transcriptional regulation of 5'-untranslated GR (NR3C1) exon 1 mRNA variants in the liver of newborn piglets

Glucocorticoids are vital for life and regulate an array of physiological functions by binding to the ubiquitously expressed glucocorticoid receptor (GR, also known as NR3C1). Previous studies demonstrate striking breed differences in plasma cortisol levels in pigs. However, investigation into the breed-dependent GR transcriptional regulation is hampered by lacking porcine GR promoter information. In this study, we sequenced 5.3 kb upstream of the translation start codon of the porcine GR gene, and identified seven alternative 5′-untranslated exons 1–4, 1–5, 1–6, 1–7, 1–8, 1–9,10 and 1–11. Among all these mRNA variants, exons 1–4 and 1–5, as well as the total GR were expressed significantly (P<0.05) higher in the liver of newborn piglets of Large White (LW) compared with Erhualian, a Chinese indigenous breed. Overall level of CpG methylation in the region flanking exons 1–4 and 1–5 did not show breed difference. However, nuclear content of Sp1, p-CREB and GR in the liver was significantly (P<0.05) higher in LW piglets, associated with enhanced binding of p-CREB, and higher level of histone H3 acetylation in 1–4 and 1–5 promoters. In contrast, GR binding to promoters of exons 1–4 and 1–5 was significantly diminished in LW piglets, implicating the presence of negative GREs. These results indicate that the difference in the hepatic expression of GR transcript variants between two breeds of pigs is determined, at least partly, by the disparity in the binding of transcription factors and the enrichment of histone H3 acetylation to the promoters.

Decreased expression of mineralocorticoid receptor mRNA and its splice variants in postmortem brain regions of patients with major depressive disorder

Appropriate signaling in the brain by the glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) is critical in regulation of the hypothalamic-pituitary-adrenal (HPA) axis, emotional arousal and cognitive performance. To date, few data exist on MR (and GR) expression in the brain of patients suffering from major depressive disorder (MDD). With the help of quantitative PCR we assessed MR and GR mRNA expression, including the splice variants MRα and MRβ, in tissue samples from the hippocampus, amygdala, inferior frontal gyrus, cingulate gyrus and nucleus accumbens. Expression levels were compared between tissue samples from six MDD patients and six non-depressed subjects. Relative to total GR, total MR mRNA expression was higher in hippocampus and lower in the amygdala, inferior frontal gyrus and nucleus accumbens. Both MRα and MRβ could be detected in all brain regions that were analyzed, although MRβ expression was low. Significantly lower expression levels (30-50%) were detected for MR or GR in hippocampal, inferior frontal gyrus and cingulate gyrus tissue from MDD patients (p < .05), while no differences were found in the amygdala or nucleus accumbens. The data show that both MRα and MRβ mRNA are expressed throughout the human limbic brain with highest expressions in the hippocampus. A decreased expression of corticosteroid receptors in specific brain regions of MDD patients could underlie HPA hyperactivity, mood and cognitive disturbances often observed in patients suffering from stress-related psychopathologies.

Histone modification profiles are predictive for tissue/cell-type specific expression of both protein-coding and microRNA genes

Background

Gene expression is regulated at both the DNA sequence level and through modification of chromatin. However, the effect of chromatin on tissue/cell-type specific gene regulation (TCSR) is largely unknown. In this paper, we present a method to elucidate the relationship between histone modification/variation (HMV) and TCSR.

Results

A classifier for differentiating CD4+ T cell-specific genes from housekeeping genes using HMV data was built. We found HMV in both promoter and gene body regions to be predictive of genes which are targets of TCSR. For example, the histone modification types H3K4me3 and H3K27ac were identified as the most predictive for CpG-related promoters, whereas H3K4me3 and H3K79me3 were the most predictive for nonCpG-related promoters. However, genes targeted by TCSR can be predicted using other type of HMVs as well. Such redundancy implies that multiple type of underlying regulatory elements, such as enhancers or intragenic alternative promoters, which can regulate gene expression in a tissue/cell-type specific fashion, may be marked by the HMVs. Finally, we show that the predictive power of HMV for TCSR is not limited to protein-coding genes in CD4+ T cells, as we successfully predicted TCSR targeted genes in muscle cells, as well as microRNA genes with expression specific to CD4+ T cells, by the same classifier which was trained on HMV data of protein-coding genes in CD4+ T cells.

Conclusion

We have begun to understand the HMV patterns that guide gene expression in both tissue/cell-type specific and ubiquitous manner.

Dynamic molecular and anatomical changes in the glucocorticoid receptor in human cortical development

The glucocorticoid receptor (GR) has a critical role in determining the brain's capacity to respond to stress, and has been implicated in the pathogenesis of psychiatric illness. We hypothesized that key changes in cortical GR occur during adolescence and young adulthood, at a time when individuals are at increased risk of developing schizophrenia, bipolar disorder and major depression. We investigated the mRNA and protein expression of GR in the dorsolateral prefrontal cortex across seven developmental time points from infancy to adulthood. GR mRNA expression, determined by microarray and quantitative real-time PCR, was lowest in neonates and peaked around young adulthood. Western blotting revealed two dynamic patterns of GRα protein expression across the lifespan, with N-terminal variants displaying differing unique patterns of abundance. GRα-A and a 67-kDa GRα isoform mirrored mRNA trends and peaked in toddlers and late in adolescence, whereas a 40-kDa isoform, very likely a GRα-D variant, peaked in neonates and decreased across the lifespan. GRα protein was localized to pyramidal neurons throughout life and most strikingly in young adulthood, but to white matter astrocytes only in neonates and infants (<130 days). These results suggest that the neonatal and late adolescent periods represent critical windows of stress pathway development, and highlight the importance of white matter astrocytes and pyramidal neurons, respectively, at these stages of cortical development. Evidence of dynamic patterns of GR isoform expression and cellular localization across development strengthens the hypothesis that windows of vulnerability to stress exist across human cortical development.

Birthweight is associated with DNA promoter methylation of the glucocorticoid receptor in human placenta

Birthweight has been associated with a number of health outcomes throughout life. Crucial to proper infant growth and development is the placenta, and alterations to placental gene function may reflect differences in the intrauterine environment which functionally contribute to infant growth and may ultimately affect the child's health. To examine if epigenetic alteration to the glucocorticoid receptor (GR) gene was linked to infant growth, we analyzed 480 human placentas for differential methylation of the GR gene exon 1F and examined how this variation in methylation extent was associated with fetal growth. Multivariable linear regression revealed a significant association (p < 0.0001) between differential methylation of the GR gene and large for gestational age (LGA) status. Our work is one of the first to link infant growth as a measure of the intrauterine environment and epigenetic alterations to the GR and suggests that DNA methylation may be a critical determinant of placental function.

Differential regulation and function of 5'-untranslated GR-exon 1 transcripts

Alternative splicing serves to increase biological diversity and adaptation. Many genes, including the glucocorticoid receptor (GR), contain multiple 5'-untranslated exons in their promoter regions that can give rise to various mRNA isoforms encoding the same protein. To date, information on the mouse GR promoter remains sparse. Here, we extensively characterize alternative first exons of the mouse GR to reveal homology to the rat and human. We further find that, although most promoters are broadly expressed in various tissues, transcription of individual promoters can be differentially regulated by growth factor- and depolarization-induced signaling. Moreover, in addition to selective promoter usage, the alternative first exon transcripts differentially control RNA stability and translation efficiency, indicative of their role in GR expression. In conclusion, the composite GR promoter enables multilayered adjustments in gene expression through transcriptional and posttranscriptional mechanisms that may serve varying physiological demands.

The prefrontal-limbic network in depression: Modulation by hypothalamus, basal ganglia and midbrain

The anterior cingulate cortex, amygdala and hippocampus form part of an interconnected prefrontal neocortical and limbic archicortical network that is dysregulated in major depressive disorders (MDD). Modulation of this prefrontal-limbic network (PLN) is principally through the hypothalamus, basal ganglia and midbrain. Here the likely mechanisms by which these modulations are affected are described and the implications of their failure for depression associated with suicidal diathesis, late-life and psychoses discussed.