Rachelle Donn

Rheumatoid arthritis association at 6q23

The Wellcome Trust Case Control Consortium (WTCCC) identified nine single SNPs putatively associated with rheumatoid arthritis at P = 1 × 10−5 − 5 × 10−7 in a genome-wide association screen. One, rs6920220, was unequivocally replicated (trend P = 1.1 × 10−8) in a validation study, as described here. This SNP maps to 6q23, between the genes oligodendrocyte lineage transcription factor 3 (OLIG3) and tumor necrosis factor-α–induced protein 3 (TNFAIP3).

Ligand modulation of REV-ERBα function resets the peripheral circadian clock in a phasic manner

The nuclear receptor REV-ERBα is a key negative-feedback regulator of the biological clock. REV-ERBα binds to ROR elements of the Bmal1 (Arntl) promoter and represses Bmal1 transcription. This stabilizing negative loop is important for precise control of the circadian pacemaker. In the present study, we identified a novel synthetic REV-ERBα ligand, which enhances the recruitment of nuclear receptor co-repressor (NCoR) to REV-ERBα. In order to explore REV-ERBα action on resetting responses of the molecular clock, we first established the rhythmic transcription profile and expression level of REV-ERBα in Rat-1 fibroblasts. When applied at different phases of the circadian oscillation to cell models containing stably transfected Bmal1::Luc or Per2::Luc, the REV-ERBα ligand induced phase-dependent bi-directional phase shifts. When the phase changes were plotted against time, a clear phase response curve was revealed, with a significant peak-to-trough amplitude of ca. 5 hours. The phase-resetting effect was also observed when the compound was applied to primary lung fibroblasts and ectopic lung slices from transgenic PER2::Luc mice. Therefore, similar regulation of REV-ERBα function by endogenous ligands, such as heme, is likely to be an important mechanism for clock resetting. In addition, we identify a new means to generate phasic shifts in the clock.

Characterization of a prolactin gene polymorphism and its associations with systemic lupus erythematosus

OBJECTIVE Hyperprolactinemia is associated with systemic lupus erythematosus (SLE), but the mechanism is unknown. Prolactin is expressed in T lymphocytes and is under the control of an alternative promoter region. We characterized a G/T single-nucleotide polymorphism (SNP) at position -1149 of this promoter and assessed its prevalence in patients with SLE. METHODS Electrophoretic mobility shift assays (EMSAs) were performed to determine DNA protein complex formation in the prolactin promoter. Transient transfection of reporter gene constructs containing the G/T promoter alleles into the Jurkat T cell line were used to determine transcription activity. Peripheral blood lymphocytes (PBLs) were treated in vitro with phytohemagglutinin (PHA) to determine levels of prolactin messenger RNA (mRNA). RESULTS EMSAs indicated that binding of a GATA-related transcription factor was altered by the G/T SNP at position -1149. Transient transfection studies in Jurkat cells showed that the G allele consistently produced higher promoter activity. PHA treatment of PBLs in vitro induced a greater increment of prolactin mRNA from patients with the GG(-1149) genotype than from those with the TT(-1149) genotype. Disease association studies in a cohort of SLE patients demonstrated an increased frequency of the prolactin -1149 G allele compared with control subjects. CONCLUSION We found a functionally significant polymorphism that alters prolactin promoter activity and mRNA levels in the lymphocytes. Altered local prolactin production by immune cells may contribute to disease progression by affecting T cell function.

Use of gene expression profiling to identify a novel glucocorticoid sensitivity determining gene, BMPRII

Wide variation in glucocorticoid (Gc) sensitivity exists between individuals which may influence susceptibility to, and treatment response of, inflammatory diseases. To determine a genetic fingerprint of Gc sensitivity 100 healthy human volunteers were polarized into the 10% most Gc‐sensitive and 10% most Gc‐resistant following a low dose dexamethasone (0.25mg) suppression test. Gene expression profiling of primary lymphocytes identified the 98 most significantly Gc regulated genes. These genes were used to build a subnetwork of Gc signaling, with 54 genes mapping as nodes, and 6 non‐Gc regulated genes inferred as signaling nodes. Twenty four of the 98 genes showed a difference in Gc response in vitro dependent on the Gc sensitivity of their donor individuals in vivo. A predictive model was built using both partial least squares discriminate analysis and support vector machines that predicted donor glucocorticoid sensitivity with 87% accuracy. Discriminating genes included bone morphogenetic protein receptor, type II (BMPRII). Transfection studies showed that BMPRII modulated Gc action. These studies reveal a broad base of gene expression that predicts Gc sensitivity and determine a Gc signaling network in human primary T lymphocytes. Furthermore, this combined gene profiling, and functional analysis approach has identified BMPRII as a modulator of Gc signaling.—Donn, R., Berry, A., Stevens, A., Farrow, S., Betts, J., Stevens, R., Clayton, C., Wang, J., Warnock, L., Worthington, J., Scott, L., Graham, S., Ray, D. Use of gene expression profiling to identify a novel glucocorticoid sensitivity determining gene, BMPRII. FASEB J. 21, 402–414 (2007)

Cytokine gene polymorphisms and susceptibility to juvenile idiopathic arthritis

Objective To investigate the involvement of candidate cytokine genes in the pathogenesis of juvenile idiopathic arthritis (JIA). Methods Single nucleotide polymorphisms and intragenic microsatellite markers within 8 candidate cytokine genes (interleukin-1α [IL-1α], IL-2, IL-4, IL-6, IL-10, interferon-α1 [IFNA1], interferon-γ [IFNG], and interferon regulatory factor 1 [IRF-1]) were investigated in 417 Caucasian patients with clinically characterized JIA and a panel of 276 unrelated, healthy Caucasian controls, all from the United Kingdom. Results A novel 3′–untranslated region (3′UTR) polymorphism in IRF-1 was found to be associated with susceptibility to JIA (corrected P = 0.002). No significant association with IL-1α, IL-2, IL-4, IL-6, IL-10, IFNA1, or IFNG was observed. Conclusion An association between JIA and a previously unreported 3′UTR polymorphism of IRF-1 was observed. This association was not found to be specific to any particular JIA subgroup. This suggests that IRF-1 may contribute to a common pathogenesis shared by all JIA patients, regardless of clinical phenotype. This is most likely to be a genetic contribution to the chronic inflammatory process that underlies JIA pathology.

HLA-DRB1 and disease outcome in multiple sclerosis.

Abstract The association between susceptibility to multiple sclerosis (MS) and the class II MHC allele HLA-DRB1*15 is well established although a possible relationship between this allele and outcome in MS is less clear. HLA-DRB1 typing was performed on 375 unrelated white patients with clinically definite MS and on 367 healthy controls. Putative associations of the gene with outcome were examined by dividing patients into two groups: those with an EDSS of 0–5.5 (mild/moderate disease) and those with an EDSS of 6–10 (severe disease). In order to minimise the effects of disease variability patients with a disease duration of at least 10 years or 15 years were examined. As subsidiary HLA-DRB1*03 and HLA-DRB1*04 associations have been previously reported, the effect of these alleles was also examined. As expected, HLA-DRB1*15 was found more frequently in patients than in controls (P < 0.000001). HLA-DRB1*15 positive patients had a significantly earlier age at onset than HLA-DRB1*15 negative patients. No significant associations were noted between HLA-DRB1*15 and outcome in the total patient group or in patients with a disease duration of 10 years or longer. In patients with a disease duration of at least 15 years HLA-DRB1*15 negative status was associated with a worse prognosis, although this did not remain significant after correction for multiple testing. It is thus likely that the contribution of HLA in MS is primarily towards onset and initial triggering mechanisms rather than influencing disease progression, chronicity and severity

Autoinflammatory genes and susceptibility to psoriatic juvenile idiopathic arthritis

Objective To investigate the association of NLRP3, NOD2, MEFV, and PSTPIP1, genes that cause 4 of the autoinflammatory hereditary periodic fever syndromes (HPFS), with juvenile idiopathic arthritis (JIA). Methods Fifty-one single-nucleotide polymorphisms (SNPs) across the 4 loci were investigated using MassArray genotyping in 950 Caucasian patients with JIA living in the UK and 728 ethnically matched healthy controls. Results Prior to Bonferroni correction for multiple testing, significant genotype associations between 6 SNPs in MEFV and JIA were observed and, in subgroup analysis, associations between 12 SNPs across all 4 loci and the subgroup of patients with psoriatic JIA were found. After Bonferroni correction for multiple testing, 2 genotype associations remained significant in the subgroup of patients with psoriatic JIA (MEFV SNP rs224204 [corrected P = 0.025] and NLRP3 SNP rs3806265 [corrected P = 0.04]). Conclusion These findings support the use of monogenic loci as candidates for investigating the genetic component of complex disease and provide preliminary evidence of association between SNPs in autoinflammatory genes and psoriatic JIA. Our findings raise the interesting possibility of a shared disease mechanism between the HPFS and psoriatic JIA, potentially involving abnormal production of interleukin-1β.

Human Macrophage Migration Inhibitory Factor A PROVEN IMMUNOMODULATORY CYTOKINE

Macrophage migration inhibitory factor (MIF) is a pro-inflammatory mediator with the ability to induce various immunomodulatory responses and override glucocorticoid-driven immunosuppression. Some of these functions have been linked to the unusual enzymatic properties of the protein, namely tautomerase and oxidoreductase activities. However, there are conflicting reports regarding the functional role of these enzymatic properties in normal physiological homeostasis and disease progression. Therefore, we have produced a highly pure, virtually endotoxin-free recombinant MIF preparation and fully characterized this using a variety of biochemical and biophysical approaches. The recombinant protein, with demonstrable enzymatic activity, was then used to systematically examine the biological activity of MIF. Surprisingly, treatment with MIF alone failed to induce cytokine expression, with the exception of IL-8. However, co-treatment of lipopolysaccharide (LPS) in conjunction with MIF produced synergistic secretion of tumor necrosis factor-α, interleukin (IL)-1, and IL-8 compared with LPS alone. The potentiating effect of MIF was seen at physiologically relevant concentrations. These data suggest that MIF has no conventional cytokine activity but, rather, acts to modulate and amplify the response to LPS.

Ultradian cortisol pulsatility encodes a distinct, biologically important signal.

Context Cortisol is released in ultradian pulses. The biological relevance of the resulting fluctuating cortisol concentration has not been explored. Objective Determination of the biological consequences of ultradian cortisol pulsatility. Design A novel flow through cell culture system was developed to deliver ultradian pulsed or continuous cortisol to cells. The effects of cortisol dynamics on cell proliferation and survival, and on gene expression were determined. In addition, effects on glucocorticoid receptor (GR) expression levels and phosphorylation, as a potential mediator, were measured. Results Pulsatile cortisol caused a significant reduction in cell survival compared to continuous exposure of the same cumulative dose, due to increased apoptosis. Comprehensive analysis of the transcriptome response by microarray identified genes with a differential response to pulsatile versus continuous glucocorticoid delivery. These were confirmed with qRT-PCR. Several transcription factor binding sites were enriched in these differentially regulated target genes, including CCAAT-displacement protein (CDP). A CDP regulated reporter gene (MMTV-luc) was, as predicted, also differentially regulated by pulsatile compared to continuous cortisol delivery. Importantly there was no effect of cortisol delivery kinetics on either GR expression, or activation (GR phosphoSer211). Conclusions Cortisol oscillations exert important effects on target cell gene expression, and phenotype. This is not due to differences in cumulative cortisol exposure, or either expression, or activation of the GR. This suggests a novel means to regulate GR function.

Impact of early disease factors on metabolic syndrome in systemic lupus erythematosus: data from an international inception cohort

Background The metabolic syndrome (MetS) may contribute to the increased cardiovascular risk in systemic lupus erythematosus (SLE). We examined the association between MetS and disease activity, disease phenotype and corticosteroid exposure over time in patients with SLE. Methods Recently diagnosed (<15 months) patients with SLE from 30 centres across 11 countries were enrolled into the Systemic Lupus International Collaborating Clinics (SLICC) Inception Cohort from 2000 onwards. Baseline and annual assessments recorded clinical, laboratory and therapeutic data. A longitudinal analysis of factors associated with MetS in the first 2 years of follow-up was performed using random effects logistic regression. Results We studied 1150 patients with a mean (SD) age of 34.9 (13.6) years and disease duration at enrolment of 24.2 (18.0) weeks. In those with complete data, MetS prevalence was 38.2% at enrolment, 34.8% at year 1 and 35.4% at year 2. In a multivariable random effects model that included data from all visits, prior MetS status, baseline renal disease, SLICC Damage Index >1, higher disease activity, increasing age and Hispanic or Black African race/ethnicity were independently associated with MetS over the first 2 years of follow-up in the cohort. Conclusions MetS is a persistent phenotype in a significant proportion of patients with SLE. Renal lupus, active inflammatory disease and damage are SLE-related factors that drive MetS development while antimalarial agents appear to be protective from early in the disease course.