Genome-wide association study identifies GIMAP as a novel susceptibility locus for Behcet's disease

Genetic predisposition to Behcet's disease mediated by a IL10RA enhancer polymorphism

Background

Several studies suggested the genetic association between IL10RA variants and susceptibility to Behcet's disease (BD). However, the precise mechanism of the association is still unknown. The purpose of this study was to investigate the mechanism underlying the genetic associations between IL10RA polymorphisms and the risk of BD.

Methods

To analyse the genetic susceptibility to BD mediated by IL10RA causal polymorphisms, we performed a study on data from our previous genome-wide association studies (GWAS), the bioinformatic analysis of post-annotation of GWAS and relevant mechanism verification experiments, including chromatin immunoprecipitation, luciferase gene-reporter assay, electrophoretic mobility shift assays, and enzyme-linked immunosorbent assay.

Results

Among 125 single nucleotide polymorphisms (SNPs) with P < 1 × 10-5 identified in our previous GWAS study on BD, rs4936415 (G/C) was predicted with the highest conserved score as an expression quantitative-trait-locus SNP for IL10RA in whole blood. There were H3K27ac and H3K4Me1 enhancer-specific enrichments around SNP rs4936415. Luciferase gene-reporter assays revealed that the rs4936415 G-allele construct showed a higher enhancer activity as compared to the empty and the C-allele construct. NF-κB1 was identified to bind the C-allele rather than the G-allele, although the enhancer SNP (rs4936415) region was found to control transcription factor binding sites. Interaction of C-allele and NF-κB1 gene construct resulted in an increased enhancer activity. BD patients showed a significantly lower serum level of the IL-10Rα.

Conclusions

This study identified a single functional causal SNP, rs4936415, in the IL10RA super-enhancer, conferring BD susceptibility. The protective G-allele of non-coding rs4936415 located inside an enhancer region of IL10RA promoted the enhancer activity and increased the expression of IL10RA.The risk C-allele is able to specifically bind NF-κB1 and, in turn, promotes enhancer activity of IL10RA. This subsequently leads to an increased expression of IL10RA. Low expression of IL-10RA suggests a relative deficiency of NF-κB1 in BD.

Genetics of vasculitis

Systemic vasculitis encompasses a wide range of conditions characterized by varying degrees of inflammation in blood vessels. Although the etiology of vasculitis remains unclear, accumulated data suggest that it is triggered in genetically predisposed individuals by the concurrence of certain environmental factors. The importance of the genetic component has been consistently supported by evidence of familial aggregation, differential prevalence by ethnicity, and multiple genetic associations with disease susceptibility and severity reported in recent years. The strongest association signals in most vasculitides correspond to genetic variants within the HLA region, suggesting an important role of the immune system in its pathophysiology. However, each type of vasculitis has distinct defining HLA association markers, likely due to disease-specific differences in antigenic drivers. Furthermore, other genetic polymorphisms located outside the HLA region play an important role in susceptibility to different vasculitides. More recent research has assessed the shared genetic susceptibility evident across different vasculitides. Future studies should focus on the identification of genetic markers that can serve as reliable biomarkers for early diagnosis, prognosis, and treatment response in systemic vasculitis.

Genome-wide association analysis reveals the associations of NPHP4, TYW1-AUTS2 and SEMA6D for Behçet's disease and HLA-B*46:01 for its intestinal involvement

BACKGROUND

Intestinal involvement in Behçet's disease (BD) is associated with poor prognosis and is more prevalent in East Asian than in Mediterranean populations. Identifying the genetic causes of intestinal BD is important for understanding the pathogenesis and for appropriate treatment of BD patients.

METHODS

We performed genome-wide association studies (GWAS) and imputation/replication genotyping of human leukocyte antigen (HLA) alleles for 1,689 Korean and Turkish patients with BD (including 379 patients with intestinal BD) and 2,327 healthy controls, followed by replication using 593 Japanese patients with BD (101 patients with intestinal BD) and 737 healthy controls. Stratified cross-phenotype analyses were performed for 1) overall BD, 2) intestinal BD, and 3) intestinal BD without association of overall BD.

RESULTS

We identified three novel genome-wide significant susceptibility loci including NPHP4 (rs74566205; P=1.36 × 10-8), TYW1-AUTS2 (rs60021986; P=1.14 × 10-9), and SEMA6D (rs4143322; P=5.54 × 10-9) for overall BD, and a new association with HLA-B*46:01 for intestinal BD (P=1.67 × 10-8) but not for BD without intestinal involvement. HLA peptide binding analysis revealed that Mycobacterial peptides, have a stronger binding affinity to HLA-B*46:01 compared to the known risk allele HLA-B*51:01.

CONCLUSIONS

HLA-B*46:01 is associated with the development of intestinal BD; NPHP4, TYW1-AUTS2, and SEMA6D are susceptibility loci for overall BD.

GIMAP5 deficiency reveals a mammalian ceramide-driven longevity assurance pathway

Preserving cells in a functional, non-senescent state is a major goal for extending human healthspans. Model organisms reveal that longevity and senescence are genetically controlled, but how genes control longevity in different mammalian tissues is unknown. Here, we report a new human genetic disease that causes cell senescence, liver and immune dysfunction, and early mortality that results from deficiency of GIMAP5, an evolutionarily conserved GTPase selectively expressed in lymphocytes and endothelial cells. We show that GIMAP5 restricts the pathological accumulation of long-chain ceramides (CERs), thereby regulating longevity. GIMAP5 controls CER abundance by interacting with protein kinase CK2 (CK2), attenuating its ability to activate CER synthases. Inhibition of CK2 and CER synthase rescues GIMAP5-deficient T cells by preventing CER overaccumulation and cell deterioration. Thus, GIMAP5 controls longevity assurance pathways crucial for immune function and healthspan in mammals.

Risk factors, clinical features and treatment of Behçet's disease uveitis

Behçet's disease is a systemic vasculitis frequently associated with intraocular inflammation. Recent findings identified independent clinical clusters in Behçet's disease, each involving distinct combinations of affected organs. Ocular Behçet's disease, mainly manifested as uveitis, is characterized as an independent cluster with a low likelihood of association with other system involvements, such as intestinal, cardiovascular, or central nervous system. A prevailing theory suggests that the pathogenesis of the disease is multifactorial, where a variety of genetic and infectious agents may interact with each other to cause the disease. Among sporadic cases, the human leukocyte antigen (HLA) genes, including HLA-B51, HLA-A26, HLA-B15, and HLA-B5701, have been found to be a key component conferring genetic susceptibility. Outside the HLA region, a set of susceptibility variants are identified, closely related to interleukin (IL)-23/IL-17 pathway, tumor necrosis factor (TNF) signaling, and pattern recognition receptor systems. Microbial infections, such as Streptococcus sanguinis, Mycobacterium tuberculosis, and Herpes simplex virus (HSV), are linked to play the triggering of disease in immunogenetically predisposed individuals. Clinically, due to the notable relapsing-remitting course of ocular Behçet's disease, the prevention of recurrent attack would be the primary treatment goal. Combination of corticosteroids and immunomodulatory drugs, such as anti-TNF agents, interferon, and conventional immunosuppressants (e.g. cyclosporine, azathioprine), have been the mainstream regimen for the disease. Future research may focus on comparing the effectiveness of immunomodulatory drugs and identifying the most suitable subgroups for a specific drug on the basis of the knowledge of the molecular heterogeneity of the disease.

Immunopathogenesis of Behçet's disease

Behçet's disease (BD) is a multi-system inflammatory disorder with vasculitic features. It does not suit any of the current pathogenesis-driven disease classifications well, a unifying concept of its pathogenesis is not unanimously conceivable at present, and its etiology is obscure. Still, evidence from immunogenetic and other studies supports the notion of a complex-polygenic disease with robust innate effector responses, reconstitution of regulatory T cells upon successful treatment, and first clues to the role of an, as of yet, underexplored adaptive immune system and its antigen recognition receptors. Without an attempt to be comprehensive, this review aims to collect and organize impactful parts of this evidence in a way that allows the reader to appreciate the work done and define the efforts needed now. The focus is on literature and notions that drove the field into new directions, whether recent or more remote.

Identification of Biomarkers Associated With CD4+ T-Cell Infiltration With Gene Coexpression Network in Dermatomyositis

Background

Dermatomyositis is an autoimmune disease characterized by damage to the skin and muscles. CD4⁺ T cells are of crucial importance in the occurrence and development of dermatomyositis (DM). However, there are few bioinformatics studies on potential pathogenic genes and immune cell infiltration of DM. Therefore, this study intended to explore CD4⁺ T-cell infiltration–associated key genes in DM and construct a new model to predict the level of CD4⁺ T-cell infiltration in DM.

Methods

GSE46239, GSE142807, GSE1551, and GSE193276 datasets were downloaded. The WGCNA and CIBERSORT algorithms were performed to identify the most correlated gene module with CD4⁺ T cells. Matascape was used for GO enrichment and KEGG pathway analysis of the key gene module. LASSO regression analysis was used to identify the key genes and construct the prediction model. The correlation between the key genes and CD4⁺ T-cell infiltration was investigated. GSEA was performed to research the underlying signaling pathways of the key genes. The key gene-correlated transcription factors were identified through the RcisTarget and Gene-motif rankings databases. The miRcode and DIANA-LncBase databases were used to build the lncRNA-miRNA-mRNA network.

Results

In the brown module, 5 key genes (chromosome 1 open reading frame 106 (C1orf106), component of oligomeric Golgi complex 8 (COG8), envoplakin (EVPL), GTPases of immunity-associated protein family member 6 (GIMAP6), and interferon-alpha inducible protein 6 (IFI6)) highly associated with CD4⁺ T-cell infiltration were identified. The prediction model was constructed and showed better predictive performance in the training set, and this satisfactory model performance was validated in another skin biopsy dataset and a muscle biopsy dataset. The expression levels of the key genes promoted the CD4⁺ T-cell infiltration. GSEA results revealed that the key genes were remarkably enriched in many immunity-associated pathways, such as JAK/STAT signaling pathway. The cisbp_M2205, transcription factor-binding site, was enriched in C1orf106, EVPL, and IF16. Finally, 3,835 lncRNAs and 52 miRNAs significantly correlated with key genes were used to build a ceRNA network.

Conclusion

The C1orf106, COG8, EVPL, GIMAP6, and IFI6 genes are associated with CD4⁺ T-cell infiltration. The prediction model constructed based on the 5 key genes may better predict the level of CD4⁺ T-cell infiltration in damaged muscle and lesional skin of DM. These key genes could be recognized as potential biomarkers and immunotherapeutic targets of DM.

Progress in the genetics of uveitis

Uveitis is the most common form of intraocular inflammatory disease and is a significant cause of visual impairment worldwide. Aetiologically, uveitis can also be classified into infectious uveitis and non-infectious uveitis. The common non-infectious forms of uveitis include acute anterior uveitis (AAU), Behçet’s disease (BD), Vogt-Koyanagi-Harada (VKH) disease, birdshot chorioretinopathy (BSCR), sarcoid uveitis. In addition, a few monogenic autoinflammatory disorders can also cause uveitis, such as Blau Syndrome and haploinsufficiency of A20 (HA20). Although the exact pathogenesis of non-infectious uveitis is still unclear, it is well-recognised that it involves both genetic and environmental risk factors. A hallmark of uveitis is its strong associations with human leucocyte antigens (HLA). For examples, AAU, BD and BSCR are strongly associated with HLA-B27, HLA-B51, and HLA-A29, respectively. In uveitis studies, multiple GWAS have successfully been conducted and led to identification of novel susceptibility loci, for example, IL23R has been identified in BD, VKH and AAU. In this review, we summarize the latest progress on the genetic associations of both HLA and non-HLA genes with major forms of uveitis, including AAU, BD, VKH, BSCR, sarcoid uveitis, Blau Syndrome and HA20, and potential future research directions.

The Roles of Monocytes and Macrophages in Behçet’s Disease With Focus on M1 and M2 Polarization

Behçet’s disease (BD) is a systemic inflammatory disease characterized by recurrent oral ulcers, genital ulcers, cutaneous inflammation, and uveitis. In addition, other potentially life-threatening lesions may occur in the intestinal tract, blood vessels, and central nervous system. This heterogeneity of the BD phenotype hampers development of a targeted treatment strategy. The pathogenesis of BD is not fully elucidated, but it is likely that genetically susceptible people develop BD in response to environmental factors, such as microbiome factors. Genetic analyses have identified various BD susceptibility loci that function in HLA-antigen presentation pathways, Th1 and Th17 cells, and autoinflammation related to monocytes/macrophages, or that increase levels of pro-inflammatory cytokines, reduce levels of anti-inflammatory cytokines, or act in dysfunctional mucous barriers. Our functional analyses have revealed that impairment of M2 monocyte/macrophage-mediated anti-inflammatory function through IL-10 is crucial to BD pathogenesis. We, therefore, propose that BD is an M1-dominant disease. In this review, we describe the roles of monocytes and macrophages in BD and consider the potential of these cells as therapeutic targets.

Global Meta-Analysis on the Association between Behcet Syndrome and Polymorphisms from the HLA Class I (A, B, and C) and Class II (DRB1, DQB1, and DPB1) Genes

Behcet syndrome (BS) is a multisystemic perivasculitis whose genetic susceptibility is linked to HLA region. We first meta-analysed all HLA class I and II genes involved in BS susceptibility in all ethnic groups worldwide. We identified 1141 articles and finally included 31 case-control studies after multiple rounds of selection. We analysed frequencies for 24 HLA-A alleles (3 alleles for HLA-A∗26 at four digits), 50 HLA-B alleles (11 alleles for HLA-B∗51 at four digits), 15 HLA-C alleles, 16 HLA-DRB1 alleles, 6 HLA-DQB1 alleles, and 15 HLA-DPB1 alleles. We meta-analysed only HLA allelic frequencies from at least three studies; therefore, we investigated 21 alleles out of 140. Going from 7.00 to 1.6 OR, we found 11 class I alleles conferring risk for BS: B∗51 : 08, B∗51, B∗51 : 01, B∗51 : 02, DQB1∗03, A∗26 : 01, Cw∗14, Cw∗15, Cw∗16, B∗15, and A∗26. Overall, the studies included populations from Europe (Greece, Spain, Italy, Germany, and Ireland), Asia (Korea, China, China Han, and Thailand), Middle East (Israel, Saudi Arabia, and Iran), and Morocco (as no other North-African population was included). We collected a number of ethnical groups sufficient to conduct an ethnic-specific meta-analysis where Europeans showed 11.25 OR for B∗51:08 and Japan 3.50 OR for A∗26 : 01. A remarkable result was that the most frequent HLA - B∗51 two-digit alleles associated with BS were different among populations: HLA - B∗51 : 08 in Europe, HLA - B∗51 : 01 in Turkey, and HLA - B∗51 : 02 in Japan. Overall, we discussed our real-world results with other imputation studies.

A genome-wide association study in Chinese identifies novel risk loci for Behcet's uveitis

PURPOSE

To explore susceptibility loci associated with uveitis in Behcet's disease (BD).

METHODS

We conducted a genome-wide association study (GWAS) primarily involving 978 BD uveitis cases and 4388 controls and a replication study of 953 BD uveitis cases and 2129 controls in the Chinese population. Luciferase reporter analysis and Chromatin immunoprecipitation (ChIP) assay were performed to explore the functional role of susceptibility genetic variants nearby ZMIZ1.

RESULTS

Three independent HLA alleles (HLA-B51, HLA-A26 and HLA-C0704) were identified in a genome-wide association with BD uveitis. In the non-HLA region, besides confirming 7 previously reported loci, we identified 22 novel susceptibility variants located in 16 loci. Meta-analysis of the Chinese cohort involving 1931 cases and 6517 controls and a published Japanese cohort of 611 cases and 737 controls showed genome-wide significant associations with ZMIZ1, RPS6KA4, IL10RA, SIPA1-FIBP-FOSL1 and VAMP1. Functional experiments demonstrated that genetic variants of ZMIZ1 were associated with an enhanced transcriptional activity and an increased expression of ZMIZ1.

CONCLUSIONS

This GWAS study identified a novel set of genetic variants that are associated with susceptibility to uveitis in BD. These findings enriched our understanding of the contribution of genetic factors to the disease.

Behcet's disease in an adult male from Nepal: A case report

This case report highlights considering Behcet's disease as a diagnosis in orogenital ulcers and uveitis, although its prevalence is unknown in Nepal due to underreporting. Also, collaboration for patient care among relevant specialties is required.

Epidemiologic and Etiological Features of Korean Patients With Behçet's Disease

Behçet's disease (BD) is a multisystem disease in which environmental factors provoke an adverse immune response in patients with genetic susceptibility towards BD, subsequently leading to a cascade of dysregulated inflammation throughout the body. It is particularly prevalent in regions spanning the ancient Silk Road, including Korea, where the first known case of BD was reported in 1961. We summarize the history, epidemiology, and clinical presentation of BD in Korea, highlighting the clinical tendencies that are particularly seen in the Korean BD population as compared to European populations. Analysis of epidemiologic trends over the past three decades in Korea shows a decreasing prevalence of complete BD and a higher prevalence of intestinal BD. We also discuss the ever-evolving understanding of the pathogenesis of BD, noting the complex interplay among genetics, environment, and immunology. The HLA-B51 allele is the most significant known genetic risk factor in developing BD. We also discuss more recently studied associations between BD and immune factors such as IL-10, IL-23R-IL-12RB2, IL-1A-IL-1B, CCR1, ERAP1, and the GIMAP cluster, the last of which has been found to have an association with BD specifically in Korea. Environmental factors such as pollution and microbials are often the inciting event in developing BD, as they trigger an imbalanced immune response in genetically susceptible individuals, one that has been often found to exhibit an aberrant Th1/Th17 response. There would be value to further studying the pathogenesis and clinical characteristics of Korean BD.

Using hierarchical similarity to examine the genetics of Behçet's disease

OBJECTIVE

Behçet's disease (BD) is a multisystem inflammatory disease that affects patients along the historic silk road. Thus far, the pathogenesis of the disease has proved elusive due to the complex genetic interactions of the disease. In this paper, we seek to clarify the genetic factors of the disease while also uncovering other diseases of interest that present with a similar genotype as BD.

RESULTS

To do this, we employ a convergent functional genomics approach by leveraging the hierarchical similarity tool available in Geneweaver. Through our analysis, we were able to ascertain 7 BD consensus genes and 16 autoimmune diseases with genetic overlap with BD. The results of our study will inform further research into the pathogenesis of Behçet's disease.

Behçet Disease: An Update for Dermatologists

Behçet disease (BD) is a chronic, relapsing, systemic vasculitis of unknown etiology with the clinical features of oral and genital ulcers, cutaneous vasculitic lesions, ocular, articular, vascular, gastrointestinal, neurologic, urogenital and cardiac involvement. BD usually appears around the third or fourth decade of life. Gender distribution is roughly equal. The disease is much more frequent in populations along the ancient 'Silk Road', extending from Eastern Asia to countries in the Middle East and the Mediterranean, compared with Western countries, but has universal distribution. Mucocutaneous manifestations are the clinical hallmarks of BD. The diagnostic criteria widely used in the disease's diagnosis are based on mucocutaneous manifestations because of their high sensitivity and/or specificity. Genetic factors are the key driver of BD pathogenesis, and HLA-B51 antigen is the strongest genetic susceptibility factor. Streptococcus sanguinis (S. sanguinis) or microbiome change can trigger innate immune system-mediated inflammation sustained by adaptive immune responses. Epistatic interaction between HLA-B51 and endoplasmic reticulum aminopeptidase 1 (ERAP1) in antigen-presenting cells disrupt T-cell homeostasis leading to downregulation of Tregs and expansion of Th1 and Th17. Thus, neutrophil activation and intense neutrophil infiltration of the affected organs develop in the early stage of inflammation. BD has a variable clinical course with unpredictable exacerbations and remissions. The disease is associated with a high mortality rate, especially in young male patients, and large-vessel, neurological, gastrointestinal system and cardiac involvement are the most important causes of death. The principal aim of treatment should be to prevent irreversible organ damage, especially during the disease's early, active phase. A better understanding of the disease's pathogenesis has provided important information on its management. New drugs, especially apremilast and anti-TNF-α agents are effective in the management of BD and have the potential to improve patients' quality of life, prognosis and survival.

Familial risk of Behçet's disease among first-degree relatives: a population-based aggregation study in Korea

OBJECTIVE

Previous studies have indicated that Behçet's disease (BD) has a genetic component, however population-level familial risk estimates are unavailable. We quantified the familial incidence and risk of BD in first-degree relatives (FDR) according to age, sex and type of family relationship.

METHODS

Using the Korean National Health Insurance database, which has full population coverage and confirmed FDR information, we constructed a cohort of 21 940 795 individuals comprising 12 million families, which were followed for a familial occurrence of BD from 2002 to 2017. Age- and sex-adjusted incidence risk ratios for BD were calculated in individuals with affected FDR compared with those without affected FDR.

RESULTS

Among the total study population, 53 687 individuals had affected FDR, of whom 284 familial cases developed BD with an incidence of 3.57/104 person-years. The familial risk (incidence) for BD was increased to 13.1-fold (2.71/104 person-years) in individuals with an affected father, 13.9-fold (3.11/104 person-years) with affected mother, 15.2-fold (4.9/104 person-years) with an affected sibling and the highest risk was 165-fold (46/104 person-years) with an affected twin. Familial risks showed age dependence, being higher in younger age groups. The sex-specific familial risk was similar in males and females.

CONCLUSION

This study provides quantified estimates of familial incidence and risk in FDR of BD patients in an entire population. Familial risks were higher within generation (sibling-sibling) vs between generations (parent-offspring). This implicates complex interactions between genetic factors and shared childhood environmental exposures in the pathogenesis of BD.

A Darwinian View of Behçet's Disease

Behçet's disease (BD) is a multisystem inflammatory disorder of unknown etiology, characterized by oral and genital ulceration, with other complications including eye, skin, joint, and central nervous system (CNS) lesions. Diagnosis is based on clinical findings, which may differ between patients. There is a strong genetic basis for BD; however, only a few genes have been associated with the disease across the geographical spread of BD. In this article, we discuss the history and combination of genes involved in this complex disease in relation to the geographical range and present our view that the disease has developed from a Darwinian perspective, with different gene polymorphisms that affect the same biological pathway. Moreover, these mutations individually are protective mechanisms against the disease relevant to each region, which affected both archaic and modern humans.

A novel gene signature for prognosis prediction and chemotherapy response in patients with pancreatic cancer

Pancreatic cancer is a lethal disease. Chemoresistance is one of the characteristics of pancreatic cancer and leads to a poor prognosis. This study built an effective predictive model for personalized treatment and explored the molecular mechanism of chemoresistance. A four-gene signature, including serine peptidase inhibitor Kazal type 1 (SPINK1), anoctamin 1 (ANO1), desmoglein 3 (DSG3) and GTPase, IMAP family member 1 (GIMAP1) was identified and associated with prognosis and chemoresistance in the training group. An internal testing dataset and the external dataset, GSE57495, were used for validation and showed a good performance of the gene signature. The high-risk group was enriched with multiple oncological pathways related to immunosuppression and was correlated with epidermal growth factor receptor (EGFR) expression, a target molecule of Erlotinib. In conclusion, this study identified a four-gene signature and established two nomograms for predicting prognosis and chemotherapy responses in patients with pancreatic cancer. The clinical value of the nomogram was evaluated by decision curve analysis (DCA). It showed that these may be helpful for clinical treatment decision-making and the discovery of the potential molecular mechanism and therapy targets for pancreatic cancer.

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.

Experimental Therapeutic Solutions for Behcet's Disease

Behcet's disease (BD) is a chronic systemic vasculitis with inflammation attacks that involve multiple organs. In addition to numerous mucocutaneous symptoms, notably recurrent oral and genital ulcers, ocular, articular, vascular, gastrointestinal, cardiac, and neurological system involvement can be observed. Mucocutaneous lesions are the primary symptom of the disease in most patients, and they usually occur before major organ involvement and other symptoms of the disease. Recognizing the disease's mucocutaneous lesions is very important to diagnose at an early stage, control with appropriate treatment and close follow-up, and prevent major organ involvement. Genome-wide association studies (GWAS) in recent years have confirmed that HLA-B*51 is the most significant genetic predisposing factor. The majority of gene polymorphisms have been detected in molecules that respond to microorganisms and genes encoding cytokines and adhesion molecules. The infectious agent S. sanguinis -commonly found in the oral mucosa of patients with BD- or the differences in the salivary or intestinal microbiome composition can trigger innate immune-mediated inflammation sustained by acquired or adaptive immune responses. In antigen-presenting cells (APCs), epistatic interactions between HLA-B*51 and endoplasmic reticulum aminopeptidase 1 (ERAP1) variants lead to the disruption of T-cell homeostasis, especially the activation of Type1 T-helper and Th17 pathway and suppression of regulatory T-cells. Recent developments to clarify the disease's etiopathogenesis provided us with a better understanding of the mechanism of action of the relatively old drugs while opening a way for many new treatment methods. Apremilast has become an important option in the treatment of mucocutaneous symptoms with its high efficacy and safety. The disease increases the mortality rate, especially in young male patients. New treatments, especially anti-TNF-α agents, have provided significant progress and decreased the mortality rates with their rapid effect and high efficacy in patients with severe organ involvement and resistance to traditional immunosuppressive and immunomodulatory therapies. The use of IL-1, IL-6, IL-17, IL-12/IL-23 antagonists in different organ involvement has gradually increased, and the quality of life has significantly improved in many patients.

Genetics of Behçet's Disease: Functional Genetic Analysis and Estimating Disease Heritability

Behçet's disease is a chronic multisystemic inflammatory disorder characterized by recurrent oral and genital ulcers. Although its etiology remains unclear, it is thought that both genetic and environmental factors contribute to the onset and progression of Behçet's disease. Here, we provide an updated view of the genetic landscape and architecture of Behçet's disease. Large-scale genetic studies performed to date revealed 21 genetic susceptibility loci associated with the disease at a GWAS level of significance (p-value = 5 × 10⁻⁸). We performed epigenetic pattern enrichment analysis in Behçet's disease associated loci, providing new insights into the molecular mechanisms underlying its pathophysiology. Our data suggest the crucial involvement of several immune cell types, including natural killer cells, monocytes, and B cells in the pathogenesis of the disease. Pathway enrichment analysis identified important biological processes involved. Using large-scale genetic data available from ~200 immune-related loci (Immunochip), we estimate Behçet's disease heritability to be at least 16%. We further used the same approach to estimate the heritability explained by the known Behçet's disease-associated loci, suggesting that they explain ~ 60% of the genetic component underlying Behçet's disease. These results indicate a significant role of non-genetic factors in causing Behçet's disease and that additional genetic variation influencing the risk of Behçet's disease remains to be identified. Finally, we calculated a cumulative genetic risk score across populations reinforcing the link between geographic variations in disease prevalence with its genetic component.

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.

Functional Genetic Polymorphisms in the IL1RL1-IL18R1 Region Confer Risk for Ocular Behçet's Disease in a Chinese Han Population

Single nucleotide polymorphisms (SNPs) in the IL1RL1–IL18R1 region are associated with various immune-mediated diseases. This study was carried out to investigate the causal variant for ocular Behçet’s disease (BD) and elucidate its target genes in the IL1RL1–IL18R1 region. Nine candidate functional SNPs were prioritized with bioinformatics analysis, followed by a two-stage association study in 694 ocular BD patients and 1,458 unaffected controls. Functional studies were performed in the peripheral blood mononuclear cells (PBMCs) of 45 healthy men and 16 active male BD patients. Genotyping was performed using the MassARRAY System. The mRNA expressions of IL1RL1, IL18R1, IL18RAP, and SLC9A4 were assayed by real-time PCR and secretion of cytokines was examined by ELISA. Significantly lower frequencies of the rs12987977 GG genotype/G allele (P_c = 8.93 × 10^–7, OR = 0.39; P_c = 2.60 × 10^–3, OR = 0.77, respectively), rs12999364 TT genotype/T allele (P_c = 3.15 × 10^–4, OR = 0.51; P_c = 1.13 × 10^–2, OR = 0.80, respectively), and rs4851569 AA genotype/A allele (P_c = 3.29 × 10^–4, OR = 0.52; P_c = 9.72 × 10^–3, OR = 0.80, respectively) were observed in BD patients compared with the controls. Functional experiments revealed a downregulation of IL1RL1, IL18R1, and SLC9A4 and a decreased secretion of IFN-γ in the anti-CD3/CD28 antibody-treated PBMCs as well as a decreased production of TNF-α in the lipopolysaccharide (LPS)-stimulated PBMCs in carriers of the protective homozygous rs12987977/GG genotype compared with the TT genotype. Our findings show that functional SNPs—rs12987977, rs12999364, and rs4851569—in the IL1RL1–IL18R1 region confer susceptibility to ocular BD in a Chinese Han population. And IL1RL1, IL18R1, and SLC9A4 may be the target genes of rs12987977.

Current State of Precision Medicine in Primary Systemic Vasculitides

Precision medicine (PM) is an emerging data-driven health care approach that integrates phenotypic, genomic, epigenetic, and environmental factors unique to an individual. The goal of PM is to facilitate diagnosis, predict effective therapy, and avoid adverse reactions specific for each patient. The forefront of PM is in oncology; nonetheless, it is developing in other fields of medicine, including rheumatology. Recent studies on elucidating the genetic architecture of polygenic and monogenic rheumatological diseases have made PM possible by enabling physicians to customize medical treatment through the incorporation of clinical features and genetic data. For complex inflammatory disorders, the prevailing paradigm is that disease susceptibility is due to additive effects of common reduced-penetrance gene variants and environmental factors. Efforts have been made to calculate cumulative genetic risk score (GRS) and to relate specific susceptibility alleles for use of target therapies. The discovery of rare patients with single-gene high-penetrance mutations informed our understanding of pathways driving systemic inflammation. Here, we review the advances in practicing PM in patients with primary systemic vasculitides (PSVs). We summarize recent genetic studies and discuss current knowledge on the contribution of epigenetic factors and extracellular vesicles (EVs) in disease progression and treatment response. Implementation of PM in PSVs is a developing field that will require analysis of a large cohort of patients to validate data from genomics, transcriptomics, metabolomics, proteomics, and epigenomics studies for accurate disease profiling. This multi-omics approach to study disease pathogeneses should ultimately provide a powerful tool for stratification of patients to receive tailored optimal therapies and for monitoring their disease activity.

Leveraging Genetic Findings for Precision Medicine in Vasculitis

Vasculitides are a heterogeneous group of low frequent disorders, mainly characterized by the inflammation of blood vessels that narrows or occlude the lumen and limits the blood flow, leading eventually to significant tissue and organ damage. These disorders are classified depending on the size of the affected blood vessels in large, medium, and small vessel vasculitis. Currently, it is known that these syndromes show a complex etiology in which both environmental and genetic factors play a major role in their development. So far, these conditions are not curable and the therapeutic approaches are mainly symptomatic. Moreover, a percentage of the patients do not adequately respond to standard treatments. Over the last years, numerous genetic studies have been carried out to identify susceptibility loci and biological pathways involved in vasculitis pathogenesis as well as potential genetic predictors of treatment response. The ultimate goal of these studies is to identify new therapeutic targets and to improve the use of existing drugs to achieve more effective treatments. This review will focus on the main advances made in the field of genetics and pharmacogenetics of vasculitis and their potential application for ameliorating long-term outcomes in patient management and in the development of precision medicine.

KIR3DL1/S1 Allotypes Contribute Differentially to the Development of Behçet Disease

Behçet disease is a chronic, relapsing-remitting autoinflammatory syndrome with a strong HLA-B*51 association. In this paper, we describe a human cohort of 267 individuals with Behçet disease and 445 matched controls from a tertiary referral center in the U.K. HLA-B*51 was confirmed as a genetic risk factor in this group (p = 0.0006, Bonferroni-Dunn correction for multiple testing [Pc] = 0.0192, odds ratio [OR] 1.92, 95% confidence interval [CI] 1.33-2.76). KIR3DL1/S1 allele-level analysis indicated that low-expressing KIR3DL1/S1 alleles in combination with KIR3DS1 increased the risk of developing Behçet disease (KIR3DL1^LOW/KIR3DS1: p = 0.0004, Pc = 0.0040, OR 2.47, 95% CI 1.43-4.25), whereas high-expressing KIR3DL1/S1 alleles in combination with a null-expressing KIR3DL1 reduced the risk of disease (KIR3DL1^HIGH/KIR3DL1^NULL: p = 0.0035, Pc = 0.0350, OR 0.53, 95% CI 0.33-0.87). Behçet disease can manifest as a purely mucocutaneous disease or can involve other organ systems such as the eyes. In the U.K. cohort studied in this study, KIR3DL1^LOW/KIR3DS1 increased the risk of ophthalmic disease (p = 1.2 × 10^-5, OR 3.92, 95% CI 2.06-7.47), whereas KIR3DL1^HIGH/KIR3DL1^NULL reduced the risk of having purely mucocutaneous disease (p = 0.0048, OR 0.45, 95% CI 0.25-0.81). To our knowledge, this is the first analysis of KIR3DL1/S1 allelic variation in Behçet disease and may provide insight into the pathogenic role of HLA-B*51 and its interaction with KIR3DL1/S1.

Behçet's Disease: An Overview of Etiopathogenesis

Behçet's disease (BD) is a systemic inflammatory disease with a chronic, relapsing-remitting course of unknown etiology hallmarked predominantly by mucocutaneous lesions and ocular involvement. BD shares some common features with autoimmune and autoinflammatory diseases and spondyloarthropathies (MHC-I-opathies). It is related to more than one pathogenic pathway triggered by environmental factors such as infectious agents in genetically predisposed subjects. The interplay between genetic background and immune system is linked to the BD presentation. Genetic factors have been investigated extensively, and several recent genome-wide association studies have confirmed HLA-B ^* 51 to be the strongest genetic susceptibility factor. However, new non-HLA susceptibility genes have been identified. Genetic variations in the genes encoding the cytokines could affect their function and be associated with disease susceptibility. Infectious agents such as Streptococcus sanguinis or the differences in salivary or gut microbiome composition can be considered to trigger the innate-derived inflammation, which is, subsequently, sustained by adaptive immune responses. Altered trimming of microbial and/or endogenous peptides by endoplasmic reticulum aminopeptidase 1 (ERAP1), presented by HLA-B ^* 51, may play a key role in BD pathogenesis causing an alteration in T cell balance with downregulation of Tregs and expansion of Th1 and Th17. The activity of neutrophils is increased and there is an intense neutrophil infiltration in the early stage of inflammation in organs affected by the disease. Association with HLA-B ^* 51 and increased IL-17 response seems to have an important role in neutrophil activity. In this paper, we provide an overview of the most recent advances on BD etiopathogenesis.

Clinical and Genetic Aspects of Behçet's Disease in Japan

Patients with Behçet's disease (BD) suffer from episodic ocular and mucocutaneous attacks, resulting in a reduced quality of life. The phenotype of Japanese BD has been changing over the past 20 years, and the rate of human leukocyte antigen (HLA)-B*51-positive complete type is decreasing while that of intestinal type is increasing. This phenotypical evolution may be related to changes in as-yet-unknown environmental factors, as the immigration influx in Japan is low. Mechanisms discovered by genome-wide association studies include ERAP1-mediated HLA class I antigen bounding pathway, autoinflammation, Th17 cells, natural killer cells, and polarized macrophages, a similar genetic architecture to Crohn's disease, ankylosing spondylitis, and psoriasis. As for treatments, management guidelines have been implemented, and the development of tumor necrosis factor (TNF) inhibitors is markedly improving the outcome of BD, but evidence supporting treatment for special-type BD is limited. The classification of BD into distinct clusters based on clinical manifestations and genetic factors is crucial to the development of optimized medicine.

Vasculitis: Decade in Review

BACKGROUND

In the last decade, we have come to better understand and manage the vasculitides. The classification of vasculitides has been revised. Genome- wide association studies and linkage analyses have been undertaken in hope of better understanding the pathogenesis of vasculitides. Comprehensive genetic studies have highlighted new pathways that may guide us in more targeted therapies. Description of the monogenic forms of vasculitis, such as deficiency of adenosine deaminase type 2 (DADA2), Haploinsufficiency of A20 (HA20), have introduced a new perspective to vasculopathies, and introduced alternative treatments for these diseases.

CONCLUSION

In this review, the important discoveries in pathogenesis and consensus treatment recommendations from the past decade will be summarized.

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.

Genetic Basis of Vasculitides with Neurologic Involvement

"Vasculitides are a heterogeneous group of inflammatory diseases of blood vessels in which genetic variation plays an important role in their susceptibility and clinical spectrum. Because of the use of novel technologies and the increase of the sample size of the study cohorts, the knowledge of the genetic background of vasculitides has considerably expanded during the last years. However, few insights have been obtained regarding the genetics underlying severe clinical phenotypes, such as those related to the nervous system. In this review the authors provide an updated overview of the genetic landscape behind vasculitis predisposition and development of neurologic manifestations."

Vasculitis Pathogenesis: Can We Talk About Precision Medicine?

Precision medicine is designing the medical care by taking into account the individual variability for each person. We have tried to address whether the existing data may guide precision medicine in primary systemic vasculitides (PSV). We have reviewed genome-wide association studies (GWAS) data, lessons from monogenic mimics of these diseases, and biomarker studies in immunoglobulin A vasculitis/Henoch–Schönlein purpura, Kawasaki disease, anti-neutrophil cytoplasmic antibody-associated vasculitis, polyarteritis nodosa (PAN), Takayasu arteritis, and Behçet’s disease (BD). GWAS provide insights about the pathogenesis of PSV while whole exome sequencing studies lead to discovery of monogenic vasculitides, phenotype of which could mimic other types of vasculitis such as PAN and BD. Monogenic vasculitides form a subgroup of vasculitis which are caused by single gene alterations and discovery of these diseases has enabled more specific therapies in these patients. With increasing number of studies on biomarkers, new targets for treatment appear and better and structured follow-up of PSV patients will become possible. Proteomics and metabolomics studies are required to better categorize our patients with PSV so that we can manage them appropriately and offer more targeted therapy.

Immune Regulatory Genes Are Major Genetic Factors to Behcet Disease: Systematic Review

Behcet's disease (BD) is a chronic refractory multi-system autoimmune disorder that occurs in a genetically susceptible host. Multiple genetic factors have been identified that may contribute to the pathogenesis of BD. The major genes with polymorphisms associated with BD include HLA-B and -A, CIITA, ERAP1, MICA, IL10, IL12A, IL12RB2, IL23R, MEFV, IRF8, TNFAIP3, REL, TLR4, NOD1,2, CCR1,CCR3, GIMAP1,2,4, KLRC4, STAT4, NCOA5, FOXP3, PSORS1C1, FUT2, UBAC2, SUMO4, ADO-EGR2, CEBPB-PTPN1, and JPKL-CNTN5. These genes encode proteins involved mainly in immune regulation and inflammation, and some in transcription and post-translational modification. A complete view of these BD-associated genes may provide a clue to this complex disease in terms of its pathogenesis and exploring potentially targeted therapies for BD.

The ocular involvement did not accompany with the genital ulcer or the gastrointestinal symptoms at the early stage of Behçet's disease

OBJECTIVES

This study aimed to identify patients with high-probability of ocular involvement of Behçet's disease (BD).

METHODS

The Japanese Ministry of Health, Labour and Welfare provided dataset of ongoing nationwide BD registration project. A patient who had confirmed BD and who was suspected to have BD was registered. We mainly analyzed newly registered patients who had the data for all demographic and diagnostic parameters regardless of fulfilment of any diagnostic criteria.

RESULTS

Among 3213 patients with confirmed or possible BD, 1382 (43.0%) were men and 1831 (57.0%) were women with a median age of 38 years (interquartile range (IQR) 30-49 years). The median duration between onset and registration was 0 year (IQR 0-3). A binomial multivariable logistic regression analysis revealed that being female (odds ratio (OR) 0.63, 95% confidence interval (CI) 0.53-0.75, p < .001), duration since onset (OR 1.33 per 10 years, 95% CI 1.18-1.51, p < .001), genital ulceration (OR 0.28, 95% CI 0.23-0.34, p < .001), and gastrointestinal symptoms (OR 0.36, 95% CI 0.30-0.44, p < .001) were related to the ocular lesion. Analyses based on data of 2800 patients who satisfied International criteria of BD, age-, sex-, duration-based subgroup analyses, analyses targeting iridocyclitis and retino-uveitis, and analysis including patients with missing data confirmed that the four factors were associated with the probability of eye involvement.

CONCLUSION

The ocular involvement did not accompany with genital ulcer or gastrointestinal symptoms at the early stage of BD.

Genetics and immunodysfunction underlying Behçet's disease and immunomodulant treatment approaches

Behçet's disease (BD) is a chronic autoimmune condition primarily prevalent in populations along the Mediterranean Sea. The exact etiology of BD has not been fully explained yet, but the disease occurrence is associated with a genetic factor, human leukocyte antigen (HLA)-B51 antigen. Among the various immunodysfunctions that are found in BD, patients are increased neutrophil motility and superoxide production, as well as elevated production of tumor necrosis factor (TNF)-α and decreased production of interleukin (IL)-10. Elevated levels of inflammatory cytokines like IL-1 and IL-17 in BD have been found associated with aberrant expression of microRNA. Gene polymorphisms in BD patients have been observed in molecules involved in responses to pathogens that can ultimately modulate the host antimicrobial response. Moreover, several single nucleotide polymorphisms (SNPs) have been reported in genes encoding chemokines and adhesion molecules; many of these changes manifest as increases in vascular inflammation and vascular damage. Lastly, genetic and epigenetic changes have been suggested as involved in the pathogenesis of BD. Modifications in DNA methylation have been found in BD patient monocytes and lymphocytes, leading to adverse function of these cells. This review presents a comprehensive compilation of the literature with regard to the immunodysfunction underlying BD, as well as of the genetics, newly described clinical specifications and novel treatment strategies using immunomodulants based on the current understanding of BD.

Vasculitis in Systemic Autoinflammatory Diseases

Autoinflammatory diseases (AID) are diseases of the innate immune system, characterized by recurrent episodes of localized or systemic inflammation. Vasculitis may accompany AID. The causes of the association of vasculitis with monogenic AID are still debated. Among the monogenic AID, Familial Mediterranean Fever (FMF) is the most common. IgA-related vasculitis (IgAV) and Polyarteritis Nodosa (PAN) involving small and/or medium-sized vessels have an increased frequency among FMF patients. There are also case reports revealing vasculitic features in Cryopyrin-Associated Periodic Fever Syndrome (CAPS), Tumor Necrosis Factor Receptor-Associated Periodic Syndrome (TRAPS), Mevalonate Kinase Deficiency (MKD), also known as Hyper IgD syndrome (HIDS), Deficiency of IL-1 Receptor Antagonist (DIRA) and Pyogenic Arthritis, Pyoderma gangrenosum, and Acne (PAPA) patients. Central nervous system vasculitis and vasculopathy have been reported in DIRA and PAPA patients whereas small vessel involvement affecting skin has been reported in CAPS, TRAPS, and MKD patients. Alternatively, vasculitis can also be a leading feature especially in the recently defined monogenic AID (Otulipenia, Deficiency of Adenosine Deaminase 2-DADA2, Haploinsufficiency of A20) and interferonopathies (STING-associated vasculopathy with onset in infancy-SAVI). DADA2 often presents as a PAN-like disease. In otulipenia, patients have painful subcutaneous nodules caused by septal panniculitis with small and medium vessel vasculitis. Haploinsufficiency of A20 (also called Familial Behcet-like Autoinflammatory Syndrome) results in a phenotype very similar to the variable vessel vasculitis of Behcet's disease with recurrent oral-genital ulcers, in addition to, skin rash, uveitis, and polyarthritis. SAVI is an autoinflammatory vasculopathy with increased Interferon (IFN) signature, causing severe skin lesions resulting in ulceration, necrosis, and in some cases, amputation. Behcet's Disease (BD) is a multifactorial polygenic AID characterized by recurrent attacks of oral-genital ulcers, skin lesions, uveitis and a unique vasculitis affecting both arteries and veins of all sizes. Many clinical features overlap with other autoinflammatory diseases and overexpression of proinflammatory cytokines is an important feature of the disease.

Regulation of Fn14 Receptor and NF-κB Underlies Inflammation in Meniere's Disease

Meniere’s disease (MD) is a rare disorder characterized by episodic vertigo, sensorineural hearing loss, tinnitus, and aural fullness. It is associated with a fluid imbalance between the secretion of endolymph in the cochlear duct and its reabsorption into the subarachnoid space, leading to an accumulation of endolymph in the inner ear. Epidemiological evidence, including familial aggregation, indicates a genetic contribution and a consistent association with autoimmune diseases (AD). We conducted a case–control study in two phases using an immune genotyping array in a total of 420 patients with bilateral MD and 1,630 controls. We have identified the first locus, at 6p21.33, suggesting an association with bilateral MD [meta-analysis leading signal rs4947296, OR = 2.089 (1.661–2.627); p = 1.39 × 10⁻⁰⁹]. Gene expression profiles of homozygous genotype-selected peripheral blood mononuclear cells (PBMCs) demonstrated that this region is a trans-expression quantitative trait locus (eQTL) in PBMCs. Signaling analysis predicted several tumor necrosis factor-related pathways, the TWEAK/Fn14 pathway being the top candidate (p = 2.42 × 10⁻¹¹). This pathway is involved in the modulation of inflammation in several human AD, including multiple sclerosis, systemic lupus erythematosus, or rheumatoid arthritis. In vitro studies with genotype-selected lymphoblastoid cells from patients with MD suggest that this trans-eQTL may regulate cellular proliferation in lymphoid cells through the TWEAK/Fn14 pathway by increasing the translation of NF-κB. Taken together; these findings suggest that the carriers of the risk genotype may develop an NF-κB-mediated inflammatory response in MD.

Behçet's disease risk association fine-mapped on the IL23R-IL12RB2 intergenic region in Koreans

Background

Behçet’s disease (BD) susceptibility had been associated with single-nucleotide polymorphisms (SNPs) in IL23R–IL12RB2, IL10, STAT4, or ERAP1 locus in Japanese, Turkish, Chinese, and other populations, but not in a Korean genome-wide association study (GWAS). We aimed to fine-map BD risk association of these four loci using extensive imputation and additional genotyping for replication.

Methods

In the discovery phase, 369 patients with BD enrolled in the previous Korean GWAS and 2000 controls retrieved from a population-based cohort of healthy Koreans were imputed for their genotypes of all SNPs in the four loci using the Asian data of the 1000 Genomes Project as reference. For genotype imputation of ERAP1 SNPs, the adjacent ERAP2 SNPs were also covered. For the 10 most significantly associated SNPs (8 imputed and 2 GWAS-genotyped), an additional 84 patients with BD and 283 healthy controls were genotyped for replication. The results from the discovery and replication phases were pooled for meta-analysis using the Mantel-Haenszel test to estimate the odds ratio (OR) and 95% confidence interval (CI).

Results

An IL23R–IL12RB2 intergenic SNP rs1495965 was significantly associated with BD risk (OR (95% CI) = 1.5 (1.3, 1.7), P = 2.5 × 10⁻⁷) in the pooled meta-analysis of the discovery (1.4 (1.2, 1.7), P = 4.9 × 10⁻⁷) and replication (1.9 (1.3, 2.6), P = 6.0 × 10⁻⁴) phases. BD risk association was fine-mapped on the intergenic region rather than the two flanking genes, as rs1495966 and rs4655535, almost perfectly correlated with rs1495965 (r² = 0.99), were also located in the same intergenic region. Consistent with previous reports, the P values tended to be lower within IL23R than IL12RB2. On the other hand, several IL10 SNPs were suggested for association in the discovery phase but all failed in the replication phase. No SNP in ERAP1–ERAP2 and STAT4 was suggested even in the discovery phase.

Conclusions

BD susceptibility association was fine-mapped on the intergenic region between IL23R and IL12RB2 as marked by three correlated SNPs, rs1495965, rs1495966, and rs4655535.

Electronic supplementary material

The online version of this article (doi:10.1186/s13075-017-1435-5) contains supplementary material, which is available to authorized users.

Is Behçet's disease a 'class 1-opathy'? The role of HLA-B*51 in the pathogenesis of Behçet's disease

The association between carriage of the human leucocyte antigen (HLA)-B*51 allele and development of Behçet's disease (BD) has been known since the early 1970s, but the exact mechanisms responsible for its role in pathogenesis remain much-debated. In an effort to explain the disease process, it has been suggested that BD constitutes one of a newly termed group of diseases, the 'MHC-I-opathies'. Other MHC-I-opathies include ankylosing spondylitis and HLA-B*27-associated spondyloarthropathies and HLA-C*0602-associated skin psoriasis. Recent work analysing the peptidome of HLA-B*51 suggests that altered peptide presentation by HLA-B*51 is vital to the disease process. In this review, we argue that immune receptor interactions with HLA-B*51 or the HLA-B*51-peptide complex could lead to development of inflammation in BD. The evidence for CD8⁺ T cell involvement is weak, and based on emerging studies it seems more likely that natural killer (NK) or other cell interactions, perhaps mediated by leucocyte immunoglobulin-like receptor (LILR) or killer immunoglobulin-like receptor (KIR) receptors, are culpable in pathogenesis. HLA misfolding leading directly to inflammation is another hypothesis for BD pathogenesis that deserves greater investigation. Ultimately, greater understanding of HLA-B*51's unique role in BD will probably lead to improved development of therapeutic strategies.

Genome-Wide Identification of Target Genes for the Key B Cell Transcription Factor Ets1

Background

The transcription factor Ets1 is highly expressed in B lymphocytes. Loss of Ets1 leads to premature B cell differentiation into antibody-secreting cells (ASCs), secretion of autoantibodies, and development of autoimmune disease. Despite the importance of Ets1 in B cell biology, few Ets1 target genes are known in these cells.

Results

To obtain a more complete picture of the function of Ets1 in regulating B cell differentiation, we performed Ets1 ChIP-seq in primary mouse B cells to identify >10,000-binding sites, many of which were localized near genes that play important roles in B cell activation and differentiation. Although Ets1 bound to many sites in the genome, it was required for regulation of less than 5% of them as evidenced by gene expression changes in B cells lacking Ets1. The cohort of genes whose expression was altered included numerous genes that have been associated with autoimmune disease susceptibility. We focused our attention on four such Ets1 target genes Ptpn22, Stat4, Egr1, and Prdm1 to assess how they might contribute to Ets1 function in limiting ASC formation. We found that dysregulation of these particular targets cannot explain altered ASC differentiation in the absence of Ets1.

Conclusion

We have identified genome-wide binding targets for Ets1 in B cells and determined that a relatively small number of these putative target genes require Ets1 for their normal expression. Interestingly, a cohort of genes associated with autoimmune disease susceptibility is among those that are regulated by Ets1. Identification of the target genes of Ets1 in B cells will help provide a clearer picture of how Ets1 regulates B cell responses and how its loss promotes autoantibody secretion.

New insights into the genetic component of non-infectious uveitis through an Immunochip strategy

BACKGROUND

Large-scale genetic studies have reported several loci associated with specific disorders involving uveitis. Our aim was to identify genetic risk factors that might predispose to uveitis per se, independent of the clinical diagnosis, by performing a dense genotyping of immune-related loci.

METHODS

613 cases and 3693 unaffected controls from three European case/control sets were genotyped using the Immunochip array. Only patients with non-infectious non-anterior uveitis and without systemic features were selected. To perform a more comprehensive analysis of the human leucocyte antigen (HLA) region, SNPs, classical alleles and polymorphic amino acid variants were obtained via imputation. A meta-analysis combining the three case/control sets was conducted by the inverse variance method.

RESULTS

The highest peak belonged to the HLA region. A more detailed analysis of this signal evidenced a strong association between the classical allele HLA-A*2902 and birdshot chorioretinopathy (p=3.21E-35, OR=50.95). An omnibus test yielded HLA-A 62 and 63 as relevant amino acid positions for this disease. In patients with intermediate and posterior uveitis, the strongest associations belonged to the rs7197 polymorphism, within HLA-DRA (p=2.07E-11, OR=1.99), and the HLA-DR15 haplotype (DRB1*1501: p=1.16E-10, OR=2.08; DQA1*0102: p=4.37E-09, OR=1.77; DQB1*0602: p=7.26E-10, OR=2.02). Outside the HLA region, the MAP4K4/IL1R2 locus reached statistical significance (rs7608679: p=8.38E-07, OR=1.42). Suggestive associations were found at five other loci.

CONCLUSIONS

We have further interrogated the association between the HLA region and non-infectious non-anterior uveitis. In addition, we have identified a new non-HLA susceptibility factor and proposed additional risk loci with putative roles in this complex condition.

Are neutrophilic dermatoses autoinflammatory disorders?

Neutrophils constitute essential players in inflammatory responses and are the first line of defence against harmful stimuli. However, dysregulation of neutrophil homeostasis can result in excessive inflammation and subsequent tissue damage. Neutrophilic dermatoses are a spectrum of inflammatory disorders characterized by skin lesions resulting from a neutrophil-rich inflammatory infiltrate in the absence of infection. The exact molecular pathophysiology of neutrophilic dermatoses has long been poorly understood. Interestingly, neutrophil-rich cutaneous inflammation is also a cardinal feature of several autoinflammatory diseases with skin involvement, the latter being caused by aberrant innate immune responses. Overactivation of the innate immune system leading to increased production of interleukin-1 family members and 'sterile' neutrophil-rich cutaneous inflammation are features of both inherited autoinflammatory syndromes with skin involvement and an increasing number of neutrophilic dermatoses. Therefore, we propose that autoinflammation may be a cause of neutrophilic dermatoses.

Survival of mature T cells in the periphery is intrinsically dependent on GIMAP1 in mice

An effective immune system depends upon the survival of mature T cells in the periphery. Members of the GIMAP family of GTPases have been proposed to regulate this homeostasis, supported by the paucity of peripheral T cells in rodents deficient for either GIMAP1 or GIMAP5. It is unclear whether this lack of T cells is a consequence of an ontological defect, causing the thymus to generate and export T cells incapable of surviving in the periphery, or whether (alternatively or additionally) mature T cells intrinsically require GIMAP1 for survival. Using the ER^T2 Cre⁺ transgene, we conditionally deleted Gimap1 in C57BL/6 mice and demonstrate that GIMAP1 is intrinsically required for the survival of mature T cells in the periphery. We show that, in contrast to GIMAP5, this requirement is independent of the T-cells' activation status. We investigated the nature of the survival defect in GIMAP1-deficient CD4⁺ T cells and show that the death occurring after GIMAP1 ablation is accompanied by mitochondrial depolarization and activation of the extrinsic apoptotic pathway. This study shows that GIMAP1 is critical for maintaining the peripheral T-cell pool in mice and offers a potent target for the treatment of T-cell-mediated diseases.

Association study of rs924080 and rs11209032 polymorphisms of IL23R-IL12RB2 in a Northern Chinese Han population with Behcet's disease

OBJECTIVES

Two genome-wide association studies (GWAS) have identified the IL-23 receptor- IL-12 receptor β2 (IL23R-IL12RB2) as the susceptibility genetic region in Turkish and Japanese population with Behçet's disease (BD). We investigated the association of this region with BD in a Northern Chinese Han population.

METHODS

A total of 407 patients with BD and 421 healthy controls were genotyped for single nucleotide polymorphisms (SNPs) rs924080 and rs11209032 using the Sequenom MassArray system.

RESULTS

Statistically significant associations with BD were detected at two SNPs namely, rs924080 and rs11209032, both, by allele analysis (OR=1.58, 95% CI=1.25-2.00, P_c=2.52×10^-4, and OR=1.45, 95% CI=1.19-1.76, P_c=3.46×10^-4, respectively), and genotype analysis (P_c=1.22×10^-3andP_c=1.77×10^-3, respectively). Significant differences were observed in the genotype frequency distribution for these SNPs under the additive, dominant and recessive models (all P_c<0.05). The haplotypes (AT and GC) formed by the two SNPs were associated with BD (all permutation P<0.05). A meta-analysis also appeared to support the association of the two SNPs with BD.

CONCLUSION

SNPs (rs924080 and rs11209032) of the IL23R-IL12RB2 region were found to be associated with BD in a Northern Chinese Han population.

Genetic Analysis with the Immunochip Platform in Behçet Disease. Identification of Residues Associated in the HLA Class I Region and New Susceptibility Loci

Behcet's disease (BD) is an immuno-mediated vasculitis in which knowledge of its etiology and genetic basis is limited. To improve the current knowledge, a genetic analysis performed with the Immunochip platform was carried out in a population from Spain. A discovery cohort comprising 278 BD cases and 1,517 unaffected controls were genotyped using the Immunochip platform. The validation step was performed on an independent replication cohort composed of 130 BD cases and 600 additional controls. The strongest association signals were observed in the HLA class I region, being HLA-B*51 the highest peak (overall P = 6.82E-32, OR = 3.82). A step-wise conditional logistic regression with classical alleles identified HLA-B*57 and HLA-A*03 as additional independent markers. The amino acid model that best explained the association, includes the position 97 of the HLA-B molecule and the position 66 of the HLA-A. Among the non-HLA loci, the most significant in the discovery analysis were: IL23R (rs10889664: P = 3.81E-12, OR = 2.00), the JRKL/CNTN5 region (rs2848479: P = 5.00E-08, OR = 1.68) and IL12A (rs1874886: P = 6.67E-08, OR = 1.72), which were confirmed in the validation phase (JRKL/CNTN5 rs2848479: P = 3.29E-10, OR = 1.66; IL12A rs1874886: P = 1.62E-08, OR = 1.61). Our results confirm HLA-B*51 as a primary-association marker in predisposition to BD and suggest additional independent signals within the class I region, specifically in the genes HLA-A and HLA-B. Regarding the non-HLA genes, in addition to IL-23R, previously reported in our population; IL12A, described in other populations, was found to be a BD susceptibility factor also in Spaniards; finally, a new associated locus was found in the JRKL/CNTN5 region.