Whole-genome screening for susceptibility genes in multicase families with Behçet's disease

Single-cell chromatin accessibility and transcriptomic characterization of Behcet's disease

Behect's disease is a chronic vasculitis characterized by complex multi-organ immune aberrations. However, a comprehensive understanding of the gene-regulatory profile of peripheral autoimmunity and the diverse immune responses across distinct cell types in Behcet's disease (BD) is still lacking. Here, we present a multi-omic single-cell study of 424,817 cells in BD patients and non-BD individuals. This study maps chromatin accessibility and gene expression in the same biological samples, unraveling vast cellular heterogeneity. We identify widespread cell-type-specific, disease-associated active and pro-inflammatory immunity in both transcript and epigenomic aspects. Notably, integrative multi-omic analysis reveals putative TF regulators that might contribute to chromatin accessibility and gene expression in BD. Moreover, we predicted gene-regulatory networks within nominated TF activators, including AP-1, NF-kB, and ETS transcript factor families, which may regulate cellular interaction and govern inflammation. Our study illustrates the epigenetic and transcriptional landscape in BD peripheral blood and expands understanding of potential epigenomic immunopathology in this disease.

Vitamin D and miRNA-155 in Behçet's Disease: Possible Association with the Disease and Disease Activity

Background

Vitamin D (vit D) controls inflammation and immunity. In Behçet's disease (BD), microRNA-155 is recognized as a significant immune response regulator. We aimed to investigate the role of vit D on immunomodulation and downregulation of inflammatory pathways associated with BD and detect the role of miRNA-155 in BD.

Methods

miRNA-155 expression by Real Time -Polymerase Chain Reaction (RT-PCR), and vit D, nuclear factor Kappa-light-chain-enhancer of activated B cells (NF-κB), and Tumor necrosis fact of TNF-α) expression by Enzyme Linked Immunosorbent Assay (ELISA) were assessed.

Results

BD patients had a significantly higher relative expression of microRNA-155 (P< 0.001), it was significantly related to vascular manifestations (P< 0.001). Vit D relative expression was significantly low in BD (P< 0.001). There was a significant rise in miRNA-155 in the active group compared to the inactive group (P< 0.001). A significant decrease in vit D levels (IU) was found in inactive and active individuals suffering from BD when compared to controls (P< 0.001). A significant rise was found in vit D levels in inactive BD cases (P< 0.001). A significant positive correlations were found between miRNA-155, NF-κB, TNF-α, and negative correlations with vit D relative expression in BD patients.

Conclusions

miRNA-155 relative expression is higher in BD is significantly related to vascular manifestations. It may have a relationship to disease activity. Vitamin D relative expression is significantly low in BD patients, which can significantly influence immunomodulatory BD therapy. Vitamin D deficiency linked to active BD.

Critical Role of Gut Microbiota and Epigenetic Factors in the Pathogenesis of Behçet's Disease

Behçet’s disease (BD) is a chronic refractory multisystem autoinflammatory disease, characterized by typical clinical features of non-specific vasculitis, oral and genital ulcers, uveitis, as well as skin lesions. The exact etiopathogenesis of BD remains unknown, existing studies have indicated that genetics and environmental factors contribute to the increased development of BD. Recently, several studies have shown that external environmental factors can affect the process of epigenetic modification, and abnormalities of epigenetic factors have been confirmed to be involved in the occurrence of BD. At the same time, abnormalities of gut microbiota (GM) in the body, have also been confirmed to participate in the pathogenesis of BD by regulating the balance of Th17/Tregs. This article reviews the pathogenesis of BD and summarizes numerous clinical studies, focusing on the mechanism of GM and epigenetic factors impacting on BD, and providing new ideas for further elucidating the pathogenesis of BD.

The Role of Natural Killer Cells in Autoimmune Diseases

Natural killer (NK) cells, the large granular lymphocytes differentiated from the common lymphoid progenitors, were discovered in early 1970’s. They are members of innate immunity and were initially defined by their strong cytotoxicity against virus-infected cells and by their important effector functions in anti-tumoral immune responses. Nowadays, NK cells are classified among the recently discovered innate lymphoid cell subsets and have capacity to influence both innate and adaptive immune responses. Therefore, they can be considered as innate immune cells that stands between the innate and adaptive arms of immunity. NK cells don’t express T or B cell receptors and are recognized by absence of CD3. There are two major subgroups of NK cells according to their differential expression of CD16 and CD56. While CD16⁺CD56^dim subset is best-known by their cytotoxic functions, CD16^-CD56^bright NK cell subset produces a bunch of cytokines comparable to CD4⁺ T helper cell subsets. Another subset of NK cells with production of interleukin (IL)-10 was named as NK regulatory cells, which has suppressive properties and could take part in immune-regulatory responses. Activation of NK cells is determined by a delicate balance of cell-surface receptors that have either activating or inhibitory properties. On the other hand, a variety of cytokines including IL-2, IL-12, IL-15, and IL-18 influence NK cell activity. NK-derived cytokines and their cytotoxic functions through induction of apoptosis take part in regulation of the immune responses and could contribute to the pathogenesis of many immune mediated diseases including ankylosing spondylitis, Behçet’s disease, multiple sclerosis, rheumatoid arthritis, psoriasis, systemic lupus erythematosus and type-1 diabetes. Dysregulation of NK cells in autoimmune disorders may occur through multiple mechanisms. Thanks to the rapid developments in biotechnology, progressive research in immunology enables better characterization of cells and their delicate roles in the complex network of immunity. As NK cells stand in between innate and adaptive arms of immunity and “bridge” them, their contribution in inflammation and immune regulation deserves intense investigations. Better understanding of NK-cell biology and their contribution in both exacerbation and regulation of inflammatory disorders is a requisite for possible utilization of these multi-faceted cells in novel therapeutic interventions.

Role of miR-146a rs2910164 and UTS2 rs228648 Genetic Variants in Behçet's Disease

Background: Behçet's disease (BD) is a chronic autoimmune inflammatory disease. Clinical studies revealed that both microRNAs and urotensin II (UTS2) play a significant role in the development of autoinflammatory diseases.Purpose: The study aimed to determine the association between miR-146a rs2910164 and UTS2 rs228648 genetic variants and BD susceptibility. In addition, the relationship between these gene variants and clinical and laboratory outcomes among Egyptian patients was investigated.Methods: The distributions of miR-146a rs2910164 and UTS2 rs228648 (p.Thr21Met) variants were analyzed in 94 patients with BD and 115 healthy control subjects using polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) and Taqman Real-time PCR techniques.Results: Frequencies of the G/G genotype and G allele of miR-146a rs2910164 variant were significantly higher in patients with BD compared with normal controls (p = .042, OR = 2.31; p = .022, OR = 1.58, respectively). The frequencies of the Thr/Thr genotype and the Thr allele of UTS2 rs228648 variant were significantly higher in subjects with BD compared with normal controls (p = .028, OR = 3.35; p = .032, OR = 1.60, respectively).Conclusion: Our results suggest that miR-146a rs2910164 and UTS2 rs228648 variants have significant roles in both the development and clinical modulation of BD in Egyptian patients.

Advances in Management of Intestinal Behçet's Disease: A Perspective From Gastroenterologists

Intestinal Behçet's disease (intestinal BD) is a rare chronic inflammatory disorder of the intestine that is characterized by recurrent intestinal manifestations with other systemic features of BD. Intestinal BD is diagnosed when a typically shaped ulcer is observed in the gastrointestinal tract, and the clinical findings meet the diagnostic criteria for BD. Owing to the small number of patients, intestinal BD is easily underestimated. On the other hand, but it often requires surgical treatment because of severe complications, including intestinal perforations or massive bleeding. The same treatment strategies used for inflammatory bowel diseases, such as Crohn's disease and ulcerative colitis, are used for intestinal BD. 5-Aminosalicylic acids, corticosteroids, and immunomodulators are considered conventional therapies, but a considerable number of patients eventually become unresponsive to these pharmaceutical treatments. Recently, biologic agents, such as anti-tumor necrosis factor-alpha inhibitors, have also been suggested as a new treatment option for intestinal BD. This article reviews the pathogenesis and diagnosis of intestinal BD and the current treatment strategies that are expected to be useful for rheumatologic specialists.

A comprehensive overview on the genetics of Behçet's disease

Behçet's disease (BD) is a systemic and inflammatory disease, characterized mainly by recurrent oral and genital ulcers, eye involvement, and skin lesions. Although the exact etiopathogenesis of BD remains unrevealed, a bulk of studies have implicated the genetic contributing factors as critical players in disease predisposition. In countries along the Silk Road, human leukocyte antigen (HLA)-B51 has been reported as the strongest genetically associated factor for BD. Genome-wide association studies, local genetic polymorphism studies, and meta-analysis of combined data from Turkish, Iranian, and Japanese populations have also identified new genetic associations with BD. Among these, other HLA alleles such as HLA-B*15, HLA-B*27, HLA-B*57, and HLA-A*26 have been found as independent risk factors for BD, whereas HLA-B*49 and HLA-A*03 are independent protective alleles for BD. Moreover, other genes have also reached the genome-wide significance level of association with BD susceptibility, including IL10, IL23R-IL12RB2, IL12A, CCR1-CCR3, STAT4, TNFAIP3, ERAP1, KLRC4, and FUT2. Also, several rare nonsynonymous variants in TLR4, IL23R, NOD2, and MEFV genes have been reported to be involved in BD pathogenesis. According to genetic determinants in the loci outside the MHC region that are contributed to the host defense, immunity, and inflammation pathways, it is suggested that immune responses to the pathogen as an important environmental factor and mucosal immunity contribute to BD susceptibility.

Behçet disease (BD) and BD-like clinical phenotypes: NF-κB pathway in mucosal ulcerating diseases

Behçet's disease (BD) is a heterogeneous multi-organ disorder in search of a unified pathophysiological theory and classification. The disease frequently has overlapping features resembling other disease clusters, such as vasculitides, spondyloarthritides and thrombophilias with similar genetic risk variants, namely HLA-B*51, ERAP1, IL-10, IL-23R. Many of the BD manifestations, such as unprovoked recurrent episodes of inflammation and increased expression of IL-1, IL-6 and TNFα, overlap with those of the hereditary monogenic autoinflammatory syndromes, positioning BD at the crossroads between autoimmune and autoinflammatory syndromes. BD-like disease associates with various inborn errors of immunity, including familial Mediterranean fever, conditions related to dysregulated NF-κB activation (eg TNFAIP3, NFKB1, OTULIN, RELA, IKBKG) and either constitutional trisomy 8 or acquired trisomy 8 in myelodysplastic syndromes. We review here the recent advances in the immunopathology of BD, BD-like diseases and the NF-κB pathway suggesting new elements in the elusive BD etiopathogenesis.

A general framework for functionally informed set-based analysis: Application to a large-scale colorectal cancer study

Genome-wide association studies (GWAS) have successfully identified tens of thousands of genetic variants associated with various phenotypes, but together they explain only a fraction of heritability, suggesting many variants have yet to be discovered. Recently it has been recognized that incorporating functional information of genetic variants can improve power for identifying novel loci. For example, S-PrediXcan and TWAS tested the association of predicted gene expression with phenotypes based on GWAS summary statistics by leveraging the information on genetic regulation of gene expression and found many novel loci. However, as genetic variants may have effects on more than one gene and through different mechanisms, these methods likely only capture part of the total effects of these variants. In this paper, we propose a summary statistics-based mixed effects score test (sMiST) that tests for the total effect of both the effect of the mediator by imputing genetically predicted gene expression, like S-PrediXcan and TWAS, and the direct effects of individual variants. It allows for multiple functional annotations and multiple genetically predicted mediators. It can also perform conditional association analysis while adjusting for other genetic variants (e.g., known loci for the phenotype). Extensive simulation and real data analyses demonstrate that sMiST yields p-values that agree well with those obtained from individual level data but with substantively improved computational speed. Importantly, a broad application of sMiST to GWAS is possible, as only summary statistics of genetic variant associations are required. We apply sMiST to a large-scale GWAS of colorectal cancer using summary statistics from ∼120, 000 study participants and gene expression data from the Genotype-Tissue Expression (GTEx) project. We identify several novel and secondary independent genetic loci.

Ulcerative Colitis in Hematological Malignancies: Paraneoplastic Manifestation or Coincidental Bystander?

Evidence of coexistence of diverse hematological malignancies—lymphoma, leukemia, multiple myeloma, and myelodysplastic syndromes—and either ulcerative colitis or Crohn's disease can be found in the literature. However, a more “systemic” effort to reach further and examine the potential of either one as paraneoplastic manifestation has not been performed. Based on these, three cases of ulcerative colitis manifesting before, simultaneously, and after the onset of different hematological malignancies are presented and critically evaluated.

Promoter methylation of Bax and Bcl2 genes and their expression in patients with Behcet's disease

BCL2 and BAX genes are a group of signalling inducer and inhibitor genes playing a key role in the process of cellular physiological death (apoptosis). These genes, through the JAK/STAT signalling pathway, affect different cytokines on cell function and subsequently lead to the pathophysiology of diseases, especially autoimmune diseases. In addition, altering the methylation of genes can affect their expression. Since the aetiology and pathology of Behcet's disease is not fully understood, the aim of this study was to determine the methylation pattern of BCL2 and BAX genes in patients with Behcet's disease and compare it with those of control group. This was a case-control study on 51 patients with Behcet and 61 control subjects. Blood samples were received from all subjects. Subsequently, the peripheral blood mononuclear cells (PBMCs) were isolated by Ficoll method and the methylation of the sites was investigated using quantitative methylation specific PCR (qMS-PCR) technique after extraction of DNA by salting out method and its examination with Nano drop. The results of methylation and expression of Bax gene suggest that the methylation level in the patient group significantly increased compared to the healthy individuals (p-value < .05). Furthermore, the results related to Bax gene expression revealed that the mean of gene expression in the patient group has decreased compared to the healthy group, and this decrease was statistically significant (p-value < .05). The rate of expression and methylation of Bcl2 did not indicate any change in the two patient and healthy groups. Given the results of this study, it can be guessed that perhaps DNA methylation is involved in certain conditions of the disease and it may result in regulation of the expression of the involved genes such as Bax gene, in the pathogenesis of the disease.

Peripheral blood mononuclear cell proteome profile in Behçet's syndrome

Behçet's syndrome (BS) is a systemic inflammatory disorder with unknown etiology. Investigation of proteome profiles of disease specific cells facilitates our understanding of the processes and related molecular pathways, especially in disorders like BS with complex inheritance pattern and clinical heterogeneity. In the current study, we evaluated the peripheral blood mononuclear cells (PBMCs) proteome of 59 patients with BS (33 in active and 26 in inactive phases) and of 28 healthy controls using two-dimensional fluorescence difference gel electrophoresis (2D-DIGE). Differentially expressed protein spots with at least twofold and/or statistically significant change (p ≤ 0.05) between active BS vs inactive BS, and also active BS vs healthy controls were identified by mass spectrometry (MALDI-TOF/TOF). Bioinformatic analyses revealed 16 differentially expressed proteins (12 of them in active vs inactive BS comparison, whereas 11 of them for active BS vs healthy control comparison) belonging to glycolysis, cytoskeleton organization, protein folding, and regulation of blood coagulation pathways. Stathmin (active BS vs inactive BS; fourfold, active BS vs healthy control; 4.7-fold) and WD repeat-containing protein-1 (active BS vs inactive BS; 2.7-fold, active BS vs healthy control; 2.7-fold), which are cytoskeleton-related proteins, were found to be lower in active patients compared to inactive patients and healthy control. Decreased levels of calreticulin (active BS vs inactive BS; 1.29-fold) and heat shock 70 kDa protein 8 (active BS vs healthy control; 1.5-fold) which are involved in protein folding and endoplasmic reticulum (ER) stress process, were observed in patients with active phase of BS. Down-regulation of protein folding and ER stress process proteins in BS patients may further support the involvement of ER stress in BS.

Genetics and Epigenetics Mechanism in the Pathogenesis of Behçet's Disease

BACKGROUND

Behçet's Disease (BD) is characterized by numerous systemic manifestations and is known for its ability to affect both, arteries and the veins. However, the etiology of BD is only partially understood, and previous studies have demonstrated a role for genetic and epigenetic factors that contribute to disease pathophysiology. Several studies have implicated T cells and monocytes in the pathogenesis of BD especially when these cells are stimulated by heat shock proteins and streptococcal antigen. Furthermore, during disease exacerbations adenosine deaminase has an important role in activating lymphocyte proliferation, maturation, and differentiation in BD. This article presents a review of the published literature mainly from the last 20 years. The topics of main concern were the role of genetic and epigenetic factors as contributing factors in disease pathophysiology.

RESULT AND CONCLUSION

The authors used MeSH terms "Behçet's disease" with "pathophysiology," "pathogenesis," "genetic" or "epigenetic" to search the PubMed database. All the relevant studies identified were included and are described according to the aforementioned subheadings.

The molecular and clinical evidence of vitamin D signaling as a modulator of the immune system: Role in Behçet's disease

Various tissues and cell types are the targets of vitamin D. However, the major targets of vitamin D in the immune system are monocytes/macrophages, dendritic cells (DCs), as well as B and T cells. Vitamin D plays an important role in the immune system modulation via regulating the expression of genes that generate pro-inflammatory mediators and inhibiting the proliferation of pro-inflammatory cells, both of which have been implicated in the pathophysiology of the inflammatory diseases. Recent studies have revealed the important relations between vitamin D and Behçet's disease (BD). Vitamin D function and its deficiency have been linked to a wide range of metabolic disorders including malignant, cardiovascular, infectious, neuromuscular, and autoimmune diseases. Here, we provide a brief analysis of the recent literature regarding immune-regulatory effects as well as clinical evidence of vitamin D influence on the molecular level in BD.

Recent Advances on Microbiota Involvement in the Pathogenesis of Autoimmunity

Autoimmune disorders derive from genetic, stochastic, and environmental factors that all together interact in genetically predisposed individuals. The impact of an imbalanced gut microbiome in the pathogenesis of autoimmunity has been suggested by an increasing amount of experimental evidence, both in animal models and humans. Several physiological mechanisms, including the establishment of immune homeostasis, are influenced by commensal microbiota in the gut. An altered microbiota composition produces effects in the gut immune system, including defective tolerance to food antigens, intestinal inflammation, and enhanced gut permeability. In particular, early findings reported differences in the intestinal microbiome of subjects affected by several autoimmune conditions, including prediabetes or overt disease compared to healthy individuals. The present review focuses on microbiota-host homeostasis, its alterations, factors that influence its composition, and putative involvement in the development of autoimmune disorders. In the light of the existing literature, future studies are necessary to clarify the role played by microbiota modifications in the processes that cause enhanced gut permeability and molecular mechanisms responsible for autoimmunity onset.

Behçet's disease: An immunogenetic perspective

Behçet's disease (BD) is a chronic and rare multisystemic disorder defined by autoimmunity and inflammatory characteristics, manifested by ocular lesions, recurrent genital and oral ulcers, skin symptoms and arthritis as well as neurological, intestinal, and vascular involvement. Despite the unknown cause of BD, there is some strong documentation for immunological, genetic, environmental, and infectious factors playing a role in the pathogenesis of BD. While the nature of the genetic variants remains unidentified, many genetic risk factors are considered to contribute to BD susceptibility. Along with human leukocyte antigen gene encoding B*51 (HLA-B*51) and areas including the major histocompatibility complex class I, genome-wide association studies have recognized numerous other BD susceptibility genes including those encoding interleukin (IL)-10, IL-12 receptor β 2 (IL-12RB2), IL-23 receptor (IL-23R), C-C chemokine receptor 1 gene, signal transducer and activator of transcription 4 (STAT4), endoplasmic reticulum aminopeptidase (ERAP1), and genes encoding killer cell lectin-like receptor family members (KLRC4-KLRK1). It is believed that BD could be considered as a disorder lying in between autoimmune and autoinflammatory syndromes. The positive responses to classical immunosuppressive agents like azathioprine and cyclosporine and involvement of autoantigens in the initiation of the disorder are the main BD features that reflect the autoimmune nature of the disorder. In this review, we address recent findings on the role of common cytokines, antibodies and immunogenetic factors in BD.

Recurrent aphthous stomatitis may be a precursor or risk factor for specific cancers: A case-control frequency-matched study

BACKGROUND

Recurrent aphthous stomatitis (RAS) is considered a prophase symptom in patients with specific cancers. This study assessed the association between RAS and subsequent onset of cancer based on a nationwide population-based database in Taiwan.

MATERIALS AND METHODS

We selected study participants from the National Health Insurance Research Database from January 2000 to December 2008. Patients in the non-RAS cohort were matched to case study patients at a 1:1 ratio through frequency matching. All participants were followed up for at least 5 years, and those who received cancer diagnoses during follow-up were identified.

RESULTS

Among 52 307 patients with and 52 304 patients without RAS, the combined hazard ratio (HR) of all subsequent cancer cases was 1.3 (95% confidence interval [CI]: 1.25-1.35, P = 0). RAS diagnosis was associated with risk for cancers of the head and neck (aHR = 2, 95% CI: 1.8-2.3), colon (aHR = 1.2, 95% CI: 1.1-1.4), liver (aHR = 1.1, 95% CI: 1-1.3), pancreas (aHR = 1.4, 95% CI: 1.1-1.7), skin (aHR = 1.4, 95% CI: 1.2-1.7), breast (aHR = 1.2, 95% CI: 1.1-1.4), and prostate (aHR = 1.5, 95% CI: 1.3-1.8), as well as hematologic cancers (aHR = 1.6, 95% CI: 1.3-1.9). A higher risk was observed for male patients (aHR = 1.35, 95% CI: 1.28-1.42) than for female patients (aHR = 1.25, 95% CI: 1.18-1.31) with RAS.

CONCLUSIONS

RAS was associated with specific cancers. Susceptible RAS patients should be screened for specific cancers.

Evaluation of SOCS1 methylation in patients with Behcet's disease

INTRODUCTION

Epigenetic discusses to inherited changes in mitosis and meiosis in the gene expression pattern which is independent of primary DNA sequence. Since, SOCS1 hyper-methylation can activate JAK / STAT signaling pathway and activation of this pathway can directly affect the impact of different cytokines on cell function and subsequently lead to pathophysiology of diseases, in particular autoimmune diseases that interact directly with the amount of cytokines and due to the fact that the cause and pathology of Behcet's disease (BD) have not ever been completely determined. So, the purpose of this study was to evaluate the methylation pattern of SOCS1 gene in patients with BD and compare them with healthy group.

METHODOLOGY

This study was a case-control study in which 50 patients with BD and 60 subjects as healthy group participated. Blood samples were collected from all participants and then Peripheral Blood Mononuclear Cells (PBMCs) were isolated through Ficoll method. After extraction of DNA by Salting out method and its analysis with Nano-drop, the methylation level of SOCS1 was examined using qMS-PCR technique.

RESULTS

Findings about methylation and gene expression in SOCS1 gene showed that the level of SOCS1 methylation was increased in patient groups compared with healthy subjects (control group) which the increase was statistically significant (p-value<0.05). Also, the results of gene expression revealed that the fold change of SOCS1 gene expression was decreased in patient group compared with healthy subjects which the decrease was statistically significant (p-value<0.05).

DISCUSSION AND CONCLUSION

According to the results of this study, it can be suggested that the DNA methylation of SOCS1 gene is likely to affect the gene expression and thereby contribute to the pathogenesis of Behcet's disease.

Dual effects of testosterone in Behcet's disease: implications for a role in disease pathogenesis

Behcet's disease (BD) exhibits more severe disease course and higher mortality among male patients. However, underlying mechanisms of gender differences in clinical manifestations and disease severity are unclear. The aim of this study was to determine whether testosterone (T) has any role on BD pathogenesis. We studied peripheral blood mononuclear cells (PBMC) and neutrophils of BD patients and controls. Functional assay of neutrophils, cytokine measurements of culture supernatants and gene expressions on both cells were analyzed before and after T incubation. Neutrophils were significantly activated after incubation with T in only BD patients. Incubation with T caused significantly elevated interleukin (IL)-12 and IL-2 in BD. Gene expression of IL-10 was significantly downregulated after incubation with T in BD, especially in male patients. The same difference was observed in IL-10 levels in culture supernatant after T. Baseline TLR4 expression was significantly higher in BD patients compared to healthy donors (HC). Toll-like receptor (TLR) 4 expression on PBMC was significantly elevated in female BD patients. ERAP1 expressions of all patients and controls were decreased under the T effect but it differed significantly between BD vs HC. Baseline IL23R expression was higher in BD males compared with females but the difference disappeared after T. When BD patients were analyzed separately, baseline C-C motif chemokine receptor1 (CCR1), STAT4, TLR4 and KLRC4 expressions were lower in males. Despite immunosuppressive behavior in healthy subjects, T causes neutrophil hyperactivation and TH1 type immune alterations in BD patients. Our results suggest that T may have a role in BD pathogenesis by altering the expression level of IL-10, TLR4, ERAP1, CCR1.

Behçet's: A Disease or a Syndrome? Answer from an Expression Profiling Study

Behçet's disease (BD) is a chronic, relapsing, multisystemic inflammatory disorder with unanswered questions regarding its etiology/pathogenesis and classification. Distinct manifestation based subsets, pronounced geographical variations in expression, and discrepant immunological abnormalities raised the question whether Behçet's is "a disease or a syndrome". To answer the preceding question we aimed to display and compare the molecular mechanisms underlying distinct subsets of BD. For this purpose, the expression data of the gene expression profiling and association study on BD by Xavier et al (2013) was retrieved from GEO database and reanalysed by gene expression data analysis/visualization and bioinformatics enrichment tools. There were 15 BD patients (B) and 14 controls (C). Three subsets of BD patients were generated: MB (isolated mucocutaneous manifestations, n = 7), OB (ocular involvement, n = 4), and VB (large vein thrombosis, n = 4). Class comparison analyses yielded the following numbers of differentially expressed genes (DEGs); B vs C: 4, MB vs C: 5, OB vs C: 151, VB vs C: 274, MB vs OB: 215, MB vs VB: 760, OB vs VB: 984. Venn diagram analysis showed that there were no common DEGs in the intersection "MB vs C" ∩ "OB vs C" ∩ "VB vs C". Cluster analyses successfully clustered distinct expressions of BD. During gene ontology term enrichment analyses, categories with relevance to IL-8 production (MB vs C) and immune response to microorganisms (OB vs C) were differentially enriched. Distinct subsets of BD display distinct expression profiles and different disease associated pathways. Based on these clear discrepancies, the designation as "Behçet's syndrome" (BS) should be encouraged and future research should take into consideration the immunogenetic heterogeneity of BS subsets. Four gene groups, namely, negative regulators of inflammation (CD69, CLEC12A, CLEC12B, TNFAIP3), neutrophil granule proteins (LTF, OLFM4, AZU1, MMP8, DEFA4, CAMP), antigen processing and presentation proteins (CTSS, ERAP1), and regulators of immune response (LGALS2, BCL10, ITCH, CEACAM8, CD36, IL8, CCL4, EREG, NFKBIZ, CCR2, CD180, KLRC4, NFAT5) appear to be instrumental in BS immunopathogenesis.

Intestinal Behçet's Disease: A True Inflammatory Bowel Disease or Merely an Intestinal Complication of Systemic Vasculitis?

Behçet's disease (BD) is a multi-systemic inflammatory disorder of an unknown etiology and shows a chronic recurrent clinical course. When the disease involves the alimentary tract, it is called intestinal BD because of its clinical importance. Intestinal BD is more frequently reported in East Asian countries than in Western or Middle Eastern countries. While any part of the gastrointestinal tract can be involved, the most common location of intestinal BD is the ileocecal area. A few, large, deep ulcerations with discrete border are characteristic endoscopic findings of intestinal BD. Currently, there is no single gold standard test or pathognomonic finding of intestinal BD. However, recently developed novel diagnostic criteria and a disease activity index have helped in assessing intestinal BD. As intestinal BD shares a lot of characteristics with inflammatory bowel disease, including genetic background, clinical manifestations, and therapeutic strategies, distinguishing between the two diseases in clinical practice is quite difficult. However, biologic agents such as anti-tumor necrosis factor α antibody shows a considerable efficacy similar to inflammatory bowel disease cases. It is important to distinguish and treat those two disease entities separately from the standpoint of precise medicine. Clinicians should require comprehensive knowledge regarding the similarities and differences between intestinal BD and inflammatory bowel disease for making an accurate clinical decision.

The impact of the IL-1β, IL-1Ra, IL-2, IL-6 and IL-10 gene polymorphisms on the development of Behcet's disease and their association with the phenotype

BACKGROUND AND OBJECTIVE

This trial was designed to investigate the effects of the interleukin (IL)-1β, IL-1Ra, IL-2, IL-6, IL-10 gene polymorphisms on Behcet's disease (BD) occurrence and the association between the polymorphisms and the phenotype.

MATERIALS AND METHOD

The study population consisted of 71 patients and 70 age and gender-matched healthy subjects. Each of the participants had 2cc of blood withdrawn, which was placed into a whole blood tube, and the DNA was obtained using the NucleoSpin(®) Blood DNA Isolation kit. To display the band lengths, the products were amplified using the primary pairs of the interleukins investigated and developed in a 2% agarose gel.

RESULTS

There were no significant differences between the groups with respect to the IL-1Ra, IL-1β, IL-2, IL-6 and the IL-10 gene polymorphism distributions. In the patient group the IL-1RN2 gene polymorphism was detected to be statistically correlated with the presence of articular involvement (p=0.0283) and the IL-1β gene polymorphism was statistically correlated with the presence of an ocular lesion (p=0.0178). The evaluation of the IL-2 gene polymorphism (p=0.0065) and IL-10 gene polymorphism (p=0.0483) distributions with respect to age of BD onset revealed a statistically significant distribution.

CONCLUSION

The statistical correlations between the articular involvement and IL-1RN, the ocular involvement and the IL-1β, and the age of disease onset and the IL-2 and IL-10 gene polymorphisms, detected for the first time in the literature, suggest that these polymorphisms could be statistically associated with the disease symptoms and used as prognostic factors.

The immunogenetics of Behçet's disease: A comprehensive review

Behçet's disease is a chronic multisystem inflammatory disorder characterized mainly by recurrent oral ulcers, ocular involvement, genital ulcers, and skin lesions, presenting with remissions and exacerbations. It is thought that both environmental and genetic factors contribute to its onset and development. Although the etiology of Behçet's disease remains unclear, recent immunogenetic findings are providing clues to its pathogenesis. In addition to the positive association of HLA-B*51, which was identified more than four decades ago, and which has since been confirmed in multiple populations, recent studies report additional independent associations in the major histocompatibility complex class I region. HLA-B*15, -B*27, -B*57, and -A*26 are independent risk factors for Behçet's disease, while HLA-B*49 and -A*03 are independent class I alleles that are protective for Behçet's disease. Genome-wide association studies have identified associations with genome-wide significance (P < 5 × 10(-8)) in the IL23R-IL12RB2, IL10, STAT4, CCR1-CCR3, KLRC4, ERAP1, TNFAIP3, and FUT2 loci. In addition, targeted next-generation sequencing has revealed the involvement of rare nonsynonymous variants of IL23R, TLR4, NOD2, and MEFV in Behçet's disease pathogenesis. Significant differences in gene function or mRNA expression associated with the risk alleles of the disease susceptibility loci suggest which genes in a disease-associated locus influence disease pathogenesis. These genes encompass both innate and adaptive immunity and confirm the importance of the predominant polarization towards helper T cell (Th) 1 versus Th2 cells, and the involvement of Th17 cells. In addition, epistasis observed between HLA-B*51 and the risk coding haplotype of the endoplasmic reticulum-associated protease, ERAP1, provides a clue that an HLA class I-peptide presentation-based mechanism contributes to this complex disease.

Advances in the genetically complex autoinflammatory diseases

Monogenic diseases usually demonstrate Mendelian inheritance and are caused by highly penetrant genetic variants of a single gene. In contrast, genetically complex diseases arise from a combination of multiple genetic and environmental factors. The concept of autoinflammation originally emerged from the identification of individual, activating lesions of the innate immune system as the molecular basis of the hereditary periodic fever syndromes. In addition to these rare, monogenic forms of autoinflammation, genetically complex autoinflammatory diseases like the periodic fever, aphthous stomatitis, pharyngitis, and cervical adenitis (PFAPA) syndrome, chronic recurrent multifocal osteomyelitis (CRMO), Behçet's disease, and systemic arthritis also fulfill the definition of autoinflammatory diseases-namely, the development of apparently unprovoked episodes of inflammation without identifiable exogenous triggers and in the absence of autoimmunity. Interestingly, investigations of these genetically complex autoinflammatory diseases have implicated both innate and adaptive immune abnormalities, blurring the line between autoinflammation and autoimmunity. This reinforces the paradigm of concerted innate and adaptive immune dysfunction leading to genetically complex autoinflammatory phenotypes.

C-type lectin domain family 12, member A: A common denominator in Behçet's syndrome and acute gouty arthritis

C-type lectin domain family 12, member A (CLEC12A) is a C-type lectin-like pattern recognition receptor capable of recognizing monosodium urate crystals. Monosodium urate crystals, the causative agents of gout are also among the danger-associated molecular patterns reflecting cellular injury/cell death. In response to monosodium urate crystals, CLEC12A effectively inhibits granulocyte and monocyte/macrophage functions and hence acts as a negative regulator of inflammation. Behçet's syndrome and gout are autoinflammatory disorders sharing certain pathological (neutrophilic inflammation), clinical (exaggerated response to monosodium urate crystals) and therapeutic (colchicine) features. We propose the hypothesis that decreased expression of CLEC12A is a common denominator in the hyperinflammatory responses observed in Behçet's syndrome and gout. Major lines of evidence supporting this hypothesis are: (1) Downregulation/deficiency of CLEC12A is associated with hyperinflammatory responses. (2) CLEC12A polymorphisms with functional and clinical implications have been documented in other inflammatory diseases. (3) Colchicine, a fundamental therapeutic agent used both in Behçet's syndrome and gout is shown to oppose the downregulation of CLEC12A. (4) Behçet's syndrome and gout are characterized by a hyperinflammatory response to monosodium urate crystals and other than gout, Behçet's syndrome is the only inflammatory condition exhibiting this exaggerated response. (5) Genomewide linkage and association studies of Behçet's syndrome collectively point to 12p12-13, the chromosomal region harboring CLEC12A. (6) Patients with severe forms of Behçet's syndrome underexpress CLEC12A with respect to patients with mild forms of the disease. If supported by well-designed, rigorous experiments, the forementioned hypothesis pertinent to CLEC12A will carry important implications for therapy, designing experimental models, and uncovering immunopathogenic mechanisms in Behçet's syndrome and gout.

Behçet's Disease: Do Natural Killer Cells Play a Significant Role?

Behçet's disease (BD) is a complex inflammatory disease, of unknown etiology. While disease pathogenesis remains unclear, a strong relationship between BD and HLA-B*51 has been established over the last 30 years. A number of theories exist regarding the cause of BD; however, few are able to account for the increased rates of HLA-B*51 positive individuals, particularly around the Mediterranean basin and Middle-East where the prevalence is highest. This review outlines current immunogenetic data on BD and the immunoregulatory role natural killer cells may play. It also describes the interaction of the killer immunoglobulin-like receptor - KIR3DL1 with its ligand Bw4, which is found on HLA-B51. Finally, CD94/NKG2D, MICA, and ERAP are outlined with regard to their potential roles in BD.

Genetics of Behçet's disease: lessons learned from genomewide association studies

PURPOSE OF REVIEW

Behçet's disease is a complex disease, and genetic susceptibility plays a critical role. This review aimed to discuss the recent genomewide association study (GWAS) findings and their implications to the pathogenesis of Behçet's disease.

RECENT FINDINGS

GWAS data confirmed the major role of HLA-B51 in Behçet's disease susceptibility, and the discovery of epistatic interactions between HLA-B51 and ERAP1 variants provided some hints about its possible pathogenic mechanisms. Investigation of human leukocyte antigen (HLA) Class I region showed weaker but independent associations around HLA-A and HLA-C regions. Genomewide studies also established associations with IL10, IL23R, CCR1, STAT4, KLRC4, GIMAP2/GIMAP4, and UBAC2 genes in Behçet's disease patients of different ethnicities. Deep resequencing of targeted genes identified additional associations with rare variants in TLR4, MEFV, and NOD2 genes.

SUMMARY

GWAS data established a major step forward by providing insights into the underlying mechanisms in Behçet's disease with the discovery of new susceptibility genes. These variations may implicate defects in the sensing and processing of microbial and endogenous danger signals as well as in the regulation of innate and adaptive immune responses in Behçet's disease. Association findings with HLA Class I antigens as well as IL23R, ERAP1, IL10, and MEFV genes also suggest shared inflammatory pathways with spondyloarthropathies.

Epistatic interaction of ERAP1 and HLA-B in Behçet disease: a replication study in the Spanish population

Behçet's disease (BD) is a multifactorial disorder associated with the HLA region. Recently, the ERAP1 gene has been proposed as a susceptibility locus with a recessive model and with epistatic interaction with HLA-B51. ERAP1 trims peptides in the endoplasmic reticulum to optimize their length for MHC-I binding. Polymorphisms in this gene have been related with the susceptibility to other immune-mediated diseases associated to HLA class I. Our aim was, the replication in the Spanish population of the association described in the Turkish population between ERAP1 (rs17482078) and BD. Additionally, in order to improve the understanding of this association we analyzed four additional SNPs (rs27044, rs10050860, rs30187 and rs2287987) associated with other diseases related to HLA class I and the haplotype blocks in this gene region. According to our results, frequencies of the homozygous genotypes for the minor alleles of all the SNPs were increased among patients and the OR values were higher in the subgroup of patients with the HLA-B risk factors, although differences were not statistically significant. Moreover, the presence of the same mutation in both chromosomes increased the OR values from 4.51 to 10.72 in individuals carrying the HLA-B risk factors. Therefore, although they were not statistically significant, our data were consistent with an association between ERAP1 and BD as well as with an epistatic interaction between ERAP1 and HLA-B in the Spanish population.

Association of Rho-kinase 1 (ROCK1) gene polymorphisms with Behçet's disease

BACKGROUND AND OBJECTIVE

Behçet's disease (BD) is a chronic inflammatory vasculitis presenting with flares and silent periods usually between 15 and 40 years of age. The aim of this study was to evaluate the possible association between Rho-kinase 1 (ROCK1) gene polymorphisms and patients with BD in a Turkish population.

METHODS

A total of 192 BD patients and 255 healthy controls of similar age and sex were enrolled in this study. Polymorphisms were analyzed in genomic DNA using a BioMark HD dynamic array system.

RESULTS

In the presence of CC genotype for rs73963110, CT genotype for rs111874856 (Val355Ile), and TC genotype for rs112130712 (Lys1054Arg) polymorphisms, the risk of BD increased 12.13-, 15.05-, and 16.28-fold, respectively (p < 0.0001). There was a lower frequency of the GA genotype of the rs112108028 (Pro1164Leu) polymorphisms in BD (10.3 %) compared with controls (39.7 %; p < 0.0001). Marked associations between these polymorphisms and the manifestations of BD were recorded.

CONCLUSION

This is the first study to show that ROCK1 gene polymorphisms may have a significant impact on susceptibility to BD.

Association Analysis of IL10, TNF-α, and IL23R-IL12RB2 SNPs with Behçet's Disease Risk in Western Algeria

Objective: We have conducted the first study of the association of interleukin (IL)-10, tumor necrosis factor alpha (TNF-α), and IL23R-IL12RB2 region single nucleotide polymorphisms (SNPs) with Behçet’s disease (BD) in Western Algeria.

Methods: A total of 51 BD patients and 96 unrelated controls from West region of Algeria were genotyped by direct sequencing for 11 SNPs including 2 SNPs from the IL10 promoter [c.-819T > C (rs1800871), c.-592A > C (rs1800872)], 6 SNPs from the TNF-α promoter [c.-1211T > C (rs1799964), c.-1043C > A (rs1800630), c.-1037C > T (rs1799724), c.-556G > A (rs1800750), c.-488G > A (rs1800629), and c.-418G > A (rs361525)], and 3 SNPs from the IL23R-IL12RB2 region [g.67747415A > C (rs12119179), g.67740092G > A (rs11209032), and g.67760140T > C (rs924080)].

Results: The minor alleles c.-819T and c.-592A were significantly associated with BD [odds ratio (OR) = 2.18; 95% confidence interval (CI) 1.28–3.73, p = 0.003]; whereas, there was weaker association between TNF-α promoter SNPs or IL23R-IL12RB2 region and disease risk.

Conclusion: Unlike the TNF-α and the IL23R-IL12RB2 region SNPs, the two IL10 SNPs were strongly associated with BD. The -819T, and -592A alleles and the -819TT, -819CT, and -592AA and -592CA genotypes seem to be highly involved in the risk of developing of BD in the population of Western Algeria.

HLA and non-HLA genes in Behçet's disease: a multicentric study in the Spanish population

Introduction

According to genome wide association (GWA) studies as well as candidate gene approaches, Behçet’s disease (BD) is associated with human leukocyte antigen (HLA)-A and HLA-B gene regions. The HLA-B51 has been consistently associated with the disease, but the role of other HLA class I molecules remains controversial. Recently, variants in non-HLA genes have also been associated with BD. The aims of this study were to further investigate the influence of the HLA region in BD and to explore the relationship with non-HLA genes recently described to be associated in other populations.

Methods

This study included 304 BD patients and 313 ethnically matched controls. HLA-A and HLA-B low resolution typing was carried out by PCR-SSOP Luminex. Eleven tag single nucleotide polymorphisms (SNPs) located outside of the HLA-region, previously described associated with the disease in GWA studies and having a minor allele frequency in Caucasians greater than 0.15 were genotyped using TaqMan assays. Phenotypic and genotypic frequencies were estimated by direct counting and distributions were compared using the χ² test.

Results

In addition to HLA-B*51, HLA-B*57 was found as a risk factor in BD, whereas, B*35 was found to be protective. Other HLA-A and B specificities were suggestive of association with the disease as risk (A*02 and A*24) or protective factors (A*03 and B*58). Regarding the non-HLA genes, the three SNPs located in IL23R and one of the SNPs in IL10 were found to be significantly associated with susceptibility to BD in our population.

Conclusion

Different HLA specificities are associated with Behçet’s disease in addition to B*51. Other non-HLA genes, such as IL23R and IL-10, play a role in the susceptibility to the disease.

Behçet's Disease, Associated Large Vessel Thrombosis, and Coexistent Thrombophilia: A Distinct Nosological Entity?

Behçet's disease (BD) represents a multisystemic disorder that combines features of immune-mediated diseases and autoinflammatory disorders. Even though it is recognized that every type or size of vessel can be affected in this disease, there is an inability to describe a coherent model that sufficiently explains the predilection of certain patients with BD for manifesting severe large vessel thrombosis. The inconsistent epidemiologic data and the complex genetic background of BD, along with the controversy of multiple international studies regarding the coexistence of thrombophilia in patients with BD and large vessel thrombosis, make us think that a percentage of these patients may actually suffer from a distinct clinical entity. The stimulus for this concept arose from the clinical observation of three male patients who were admitted to our clinic due to extended vena cava thrombosis. On the occasion of those clinically and laboratory resembling cases, we performed a literature review concerning the epidemiology of BD, associated thrombosis, and coexistent thrombophilic factors, in order to present some evidence, which sustains our hypothesis that certain patients with large vessel thrombosis, who share features of BD and coexistent thrombophilia, should actually be further investigated for the possibility of suffering from a distinct nosological entity.

Identification of a susceptibility locus in STAT4 for Behçet's disease in Han Chinese in a genome-wide association study

OBJECTIVE

To identify susceptibility loci for Behçet's disease (BD) and elucidate their functional role.

METHODS

A genome-wide association study (GWAS) and functional studies were conducted. A total of 149 patients and 951 controls were enrolled in the initial GWAS, and 554 patients and 1,159 controls were enrolled in the replication study. Real-time polymerase chain reaction, luciferase reporter assay, and enzyme-linked immunosorbent assay were performed.

RESULTS

Our GWAS and replication studies identified a susceptibility locus around STAT4 (single-nucleotide polymorphisms [SNPs] rs7574070, rs7572482, and rs897200; P = 3.36 × 10(-7) to 6.20 × 10(-9) ). Increased expression of STAT4 was observed in individuals carrying the rs897200 risk genotype AA. Consistent with the idea that STAT4 regulates the production of interleukin-17 (IL-17) and interferon-γ, IL17 messenger RNA and protein levels were increased in individuals carrying the rs897200 risk genotype AA. Interestingly, the risk allele A of rs897200 creates a putative transcription factor binding site. To test whether it directly affects STAT4 transcription, an in vitro luciferase reporter gene assay was performed. Higher transcription activity was observed in individuals carrying the risk allele A, suggesting that rs897200 is likely to directly affect STAT4 expression. Additionally, 2 SNPs, rs7574070 and rs7572482, which are tightly linked with rs897200, were cis-expression quantitative trait loci (eQTL) SNPs, suggesting that SNP rs897200 is an eQTL SNP. Most importantly, the clinical disease severity score was higher in individuals with the rs897200 risk genotype AA.

CONCLUSION

These findings strongly suggest that STAT4 is a novel locus underlying BD. We propose a model in which up-regulation of STAT4 expression and subsequent STAT4-driven production of inflammatory cytokines, such as IL-17, constitute a potential pathway leading to BD.

Thr21Met (T21M) but not Ser89Asn (S89N) polymorphisms of the urotensin-II (UTS-II) gene are associated with Behcet's disease (BD)

Behcet's disease (BD) is multisytemic vasculitis or chronic inflammation that may lead to various autoimmune and autoinflammatory syndromes. Exact etiopathogenesis of BD has not been clarified yet. Urotensin II (UTS-II) is predominantly a vasoactive peptide and Thr21Met polymorphism in UTS-II gene was proved to increasing in some autoimmune diseases. Considering these, our objective was to evaluate whether two UTS-II gene polymorphisms (Thr21Met and Ser89Asn) were responsible in genetic susceptibility to BD in a Turkish population. A total of 198 patients with BD and 275 healthy controls were enrolled. We analyzed the genotype and allele frequencies of two UTS-II gene polymorphisms, Thr21Met and Ser89Asn, in BD patients and in controls. We found that Thr21Met but not Ser89Asn polymorphisms of the UTS-II gene were markedly associated with the risk of developing BD (p<0.0001), The Met21Met genotype was less common among BD patients (6.1% in patients vs. 17.1% in controls; p<0.0001). There was also an increase in the 21Thr allele (54.8% in BD patients vs. 43.8% in controls) and a decrease in 21Met allele frequencies (45.2% in controls vs. 56.2% in patients) in the BD groups (p<0.0044). To the best of our knowledge, for the first time in the literature, our study claims that there is an association between Thr21Met, and not between Ser89Asn polymorphisms in the UTS-II gene and BD. These results put a new player to the field of undiscovered pathogenesis of BD and hopefully provide new insights to the treatment options.

Genome-wide association analysis identifies new susceptibility loci for Behçet's disease and epistasis between HLA-B*51 and ERAP1

Patients with Behçet's disease (BD) suffer from episodic inflammation often affecting the orogenital mucosa, skin, and eyes. To discover new BD-susceptibility loci, we performed a genome-wide association study (GWAS) of 779,465 SNPs with imputed genotypes in 1,209 Turkish BD patients and 1,278 controls. We identified novel associations at CCR1, STAT4, and KLRC4. Additionally, two SNPs in ERAP1, encoding ERAP1 p.Asp575Asn and p.Arg725Gln, recessively conferred disease risk. These findings replicated in 1,468 independent Turkish and/or 1,352 Japanese samples (combined meta-analysis p < 2 × 10⁻⁹). We also found evidence for interaction between HLA-B*51 and ERAP1 (p = 9 × 10⁻⁴). The CCR1 and STAT4 variants were associated with gene expression differences. Three risk loci shared with ankylosing spondylitis and psoriasis (MHC-I, ERAP1, and IL23R, and the MHC-I-ERAP1 interaction), as well as two loci shared with inflammatory bowel disease (IL23R and IL10) implicate shared pathogenic pathways in the spondyloarthritides and BD.

Replication study confirms the association between UBAC2 and Behçet's disease in two independent Chinese sets of patients and controls

Introduction

The purpose of this study was to replicate genetic factors associated with the susceptibility to Behçet's disease (BD). We conducted a two-stage candidate genes association and functional study, involving 477 BD patients and 1,334 normal controls of Chinese Han descent.

Methods

The genotyping of five candidate genes/loci, including LOC100129342, KIAA1529, CPVL, UBASH3B and UBAC2, were performed using TaqMan single nucleotide polymorphism (SNP) assays. Real-time PCR and luciferase reporter assay were performed to test the function of the identified promoter polymorphism. The main outcome measures were genotype frequencies and expression levels in BD patients.

Results

The first-stage study results showed that UBAC2 (rs9513584, Pc = 0.018, OR = 1.4), but not LOC100129342, KIAA1529, CPVL, UBASH3B was associated with the susceptibility to BD in Chinese Han. The fine-mapping association study of UBAC2 identified six risk SNPs for BD in the Chinese cohort; three of them were verified in validation study (rs3825427, first-stage Pc = 2.2 × 10^-3, second-stage Pc = 9.3 × 10^-3, combined Pc = 6.9 × 10^-6; rs9517668, first-stage Pc = 1.7 × 10^-3, second-stage Pc = 0.03, combined Pc = 3.3 × 10^-4; rs9517701, first-stage Pc = 5.1 × 10^-3, second-stage Pc = 9.0 × 10^-3, combined Pc = 2.9 × 10^-5; respectively). Functional analysis showed that the risk T allele of the promoter polymorphism rs3825427 had a significantly lower promoter activity than the non-risk G allele (P = 0.002) and a decreased expression of UBAC2 transcript variant 1 in peripheral blood mononuclear cells (PBMCs) and skin of normal controls carrying the risk T allele than that in individuals with the G allele (P = 0.045, P = 0.025; respectively). The mRNA expression of UBAC2 transcript variant 1 was significantly decreased in PBMCs and skin of BD patients as compared with controls (P = 0.025; P = 0.047, respectively). The mRNA expression of UBAC2 transcript variant 2 was significantly increased in skin of BD patients as compared with controls (P = 0.004).

Conclusions

This study replicates a predisposition gene to BD, UBAC2, and suggests that UBAC2 may be involved in the development of BD through its transcriptional modulation.

No association of PTPN22 polymorphisms with susceptibility to ocular Behcet's disease in two Chinese Han populations

BACKGROUND

Behcet's disease is known as a recurrent, multisystem inflammation and immune-related disease. Protein tyrosine phosphatase non-receptor 22 (PTPN22) is a key negative regulator of T lymphocytes and polymorphisms of the PTPN22 gene have been shown to be associated with various immune-related diseases. The present study was performed to assess the association between PTPN22 polymorphisms and Behcet's disease in two Chinese Han populations.

METHODOLOGY/PRINCIPAL FINDINGS

A total of 516 patients with ocular Behcet's disease and 690 healthy controls from two Chinese Han populations were genotyped by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method for three single nucleotide polymorphisms (SNPs). Hardy-Weinberg equilibrium was tested using the χ(2) test. Genotype frequencies were estimated through direct counting. Allele and genotype frequencies were compared between patients and controls using logistic regression analysis. The results revealed that there was no association between the tested three PTPN22 SNPs (rs2488457, rs1310182 and rs3789604) and ocular Behcet's disease (p>0.05). Categorization analysis according to the clinical features did not show any association of these three polymorphisms with these parameters (p>0.05).

CONCLUSIONS/SIGNIFICANCE

The investigated PTPN22 gene polymorphisms (rs2488457, rs1310182 and rs3789604) were not associated with ocular Behcet's disease in two Chinese Han populations, and showed that it may be different from other classical autoimmune diseases. More studies are needed to confirm these findings for Behcet's disease in other ethnic backgrounds.

Replication of a microsatellite genome-wide association study of Behcet's disease in a Korean population

OBJECTIVE

Behçet's disease is one of the major aetiologies of uveitis causing blindness in Asian countries. A genome-wide association study identified six microsatellite markers as disease susceptibility loci for Japanese patients with Behçet's disease. To confirm our recent results, these microsatellite markers were examined in a Korean population as a replication study.

METHODS

Study participants included 119 Behçet's disease patients and 141 controls. All were enrolled in Korea. Association between the six reported microsatellite markers (D3S0186i, D6S0014i, D6S0032i, 536G12A, D12S0645i and D22S0104i) and Behçet's disease was analysed. HLA-B was genotyped by sequence-based typing methods.

RESULTS

A microsatellite marker located near the HLA-B region demonstrated significant association with Behçet's disease (P = 0.028). The genotype and phenotype frequencies of the HLA-B*51 gene were significantly increased in patients (23.1 and 39.5%, respectively) compared with healthy controls (11.2 and 20.1%, respectively; P < 0.001).

CONCLUSION

Microsatellite analysis revealed that the HLA-B*51 gene was strongly associated with Behçet's disease in a Korean population.

Behçet's disease and genes within the major histocompatibility complex region

The role of genetic background in the development of Behçet's disease (BD) is best reflected by the strong association between HLA-B*51 and BD that has been demonstrated across various ethnic groups. The contributions made by other HLA or non-HLA genes to disease susceptibility have been suggested by the results of a number of gene association studies, although the true associations between the genes located within the major histocompatibility complex (MHC) region and BD have often been doubted due to the possibility of linkage disequilibrium of those genes with HLA-B*51. The presence of a true susceptibility gene in the vicinity of HLA-B*51 has also been extensively investigated because of the limited evidence that directly relates HLA-B*51 to the pathogenesis of BD. However, recent genome-wide association studies have confirmed that HLA-B*51 is primarily associated with BD and that there are multiple susceptibility loci other than HLA-B*51. In this review, we discuss BD-associated genes within the MHC region and their biological roles in the pathogenesis of BD.

Genetics of Behçet's Disease

Behçet's disease (BD) is a systemic inflammatory disorder characterized mainly by recurrent oral and genital ulcers and eye involvement. Although the pathogenesis remains poorly understood, a variety of studies have demonstrated that genetic predisposition is a major factor in disease susceptibility. Peculiar geographical distribution of BD along the ancient Silk Road has been regarded as evidence supporting genetic influence. The observed aggregation of BD in families of patients with BD is also supportive for a genetic component in its etiology. HLA-B51 (B510101 subtype) is the most strongly associated genetic marker for BD in countries on the Silk Road. In recent years, several genome-wide association studies and genetic polymorphism studies have also found new genetic associations with BD, which may have a supplementary role in disease susceptibility and/or severity. The author reviewed the HLA and non-HLA genetic association studies.

Associations between the HLA-A polymorphism and the clinical manifestations of Behcet's disease

INTRODUCTION

The objective was to investigate associations between the HLA-A gene and Behcet's disease (BD) and its clinical manifestations.

METHODS

Genotyping for the HLA-A locus was performed using the polymerase chain reaction-Luminex typing method in 223 BD patients and 1,398 healthy controls.

RESULTS

The phenotypic frequencies of HLA-A*02:07 (odds ratio (OR) = 2.03, P = 0.002), A*26:01 (OR = 1.85, P = 0.008), and A*30:04 (OR = 2.51, P = 0.006) tended to be higher in BD patients than in normal controls, but the frequency of A*33:03 (OR = 0.59, P = 0.003) tended to be lower in BD patients. A meta-analysis adopting our and the Japanese data confirmed the associations of HLA-A*02:07, A*26:01, and A*33:03 with BD. Furthermore, the frequencies of the HLA-A*02:07, A*26:01, and A*30:04 were significantly higher in patients with skin lesions (OR = 2.37, P < 0.0005, Pc < 0.012) and arthritis (OR = 2.32, P = 0.002, Pc = 0.048), with uveitis (OR = 3.01, P < 0.0005, Pc < 0.012), and with vascular lesions (OR = 9.80, P < 0.0005, Pc < 0.012) and a positive pathergy test (OR = 4.10, P = 0.002, Pc = 0.048), respectively, than in controls. In HLA-B*51 non-carriers, these associations were also significant, being much stronger between HLA-A*26:01 and uveitis (OR = 4.19, P < 0.0005, Pc < 0.012) and between HLA-A*30:04 and vascular lesions (OR = 13.97, P < 0.00005, Pc < 0.0012). In addition, HLA-A*30:04 was associated with genital ulcers in HLA-B*51 non-carriers (OR = 3.89, P = 0.002, Pc = 0.048).

CONCLUSIONS

HLA-A*02:07, A*26:01, and A*30:04 were associated with increased risk for BD, while HLA-A*33:03 with decreased risk. HLA-A*02:07, A*26:01, and A*30:04 were associated with skin lesions and arthritis, with uveitis, and with vascular lesions, genital ulcers, and a positive pathergy test, respectively.

Genetic susceptibility to Behcet's disease: role of genes belonging to the MHC region

OBJECTIVE

To review the progress in the field of MHC-related genetic susceptibility to Behçet's disease (BD).

METHOD

Systematic review of the English literature between 1 January 1980 and 31 January 2010 using Medline. Case-control, population-based, observational cohort studies investigating the association between BD and HLA-B*51 subtypes, classical and non-classical HLA alleles and other HLA-related genes were selected. The geographical distribution of BD and these susceptibility genes was also taken into consideration. Case and familial case reports were excluded except for case series with more than two patients.

RESULTS

Ninety articles plus 17 obtained from other sources were included in the systematic review. We have found high evidence that a core component of genetic susceptibility to BD is within the MHC region being primarily related to an HLA-B*51 subtype: HLA-B*5101/B*510101. Moreover, HLA-A*26, HLA-B*15, HLA-B*5701 and TNF-α -1031C were independently associated with BD. Data suggest that other HLA (HLA-C, HLA-DR) and HLA-related [MHC Class I chain-related gene A (MIC-A), TNF-α] genes may play a role in BD co-susceptibility or pathogenesis. Finally, the distinctive geographical distribution of BD suggested an evolutionary selection of HLA-B*51 subtypes as the major susceptibility factors for BD.

CONCLUSION

Further studies must be addressed to clarify the functional relevance of the different genes found to be associated with disease susceptibility and the potential interactions between genes located within and outside the MHC region.

[Behçet's disease in obstetrics and gynecology]

Behçet's disease is a multisystemic disease of unknown origin characterized by a recurrent bipolar aphtosis (oral and genital) associated with vascular, digestive or articular symptoms. Gynecologists can be faced to this disease at any time of the life of their patients, including during the pregnancy. Given that the first demonstrations of the disease can be genital, they are in the front line to evoke this diagnosis. They thus have to know the main characteristics of the disease to make the diagnosis and to organize a multidisciplinary management. During pregnancy, the treatment of the disease is to be adapted to avoid teratogenic drugs, and adapt the doses of the treatment.