Dense genotyping of immune-related loci implicates host responses to microbial exposure in Behçet's disease susceptibility.

We analyzed 1,900 Turkish Behçet's disease cases and 1,779 controls genotyped with the Immunochip. The most significantly associated SNP was rs1050502, a tag SNP for HLA-B*51. In the Turkish discovery set, we identified three new risk loci, IL1A-IL1B, IRF8, and CEBPB-PTPN1, with genome-wide significance (P < 5 × 10-8) by direct genotyping and ADO-EGR2 by imputation. We replicated the ADO-EGR2, IRF8, and CEBPB-PTPN1 loci by genotyping 969 Iranian cases and 826 controls. Imputed data in 608 Japanese cases and 737 controls further replicated ADO-EGR2 and IRF8, and meta-analysis additionally identified RIPK2 and LACC1. The disease-associated allele of rs4402765, the lead marker at IL1A-IL1B, was associated with both decreased IL-1α and increased IL-1ß production. ABO non-secretor genotypes for two ancestry-specific FUT2 SNPs showed strong disease association (P = 5.89 × 10-15). Our findings extend the list of susceptibility genes shared with Crohn's disease and leprosy and implicate mucosal factors and the innate immune response to microbial exposure in Behçet's disease susceptibility.

IL10 low-frequency variants in Behçet's disease patients.

AIM: To explain the missing heritability after the genome-wide association studies era, sequencing studies allow the identification of low-frequency variants with a stronger effect on disease risk. Common variants in the interleukin 10 gene (IL10) have been consistently associated with Behçet's disease (BD) and the goal of this study is to investigate the role of low-frequency IL10 variants in BD susceptibility. METHODS: To identify IL10 low-frequency variants, a discovery group of 50 Portuguese BD patients were Sanger-sequenced in a 7.7 kb genomic region encompassing the complete IL10 gene, 0.9 kb upstream and 2 kb downstream, and two conserved regions in the putative promoter. To assess if the novel variants are BD- and/or Portuguese-specific, they were assayed in an additional group of BD patients (26 Portuguese and 964 Iranian) and controls (104 Portuguese and 823 Iranian). RESULTS: Rare IL10 coding variants were not detected in BD patients, but we identified 28 known single nucleotide polymorphisms with minor allele frequencies ranging from 0.010 to 0.390, and five novel non-coding variants in five heterozygous cases. ss836185595, located in the IL10 3' untranslated region, was also detected in one Iranian control individual and therefore is not specific to BD. The remaining novel IL10 variants (ss836185596 and ss836185602 in intron 3, ss836185598 and ss836185604 in the putative promoter region) were not found in the replication dataset. CONCLUSION: This study highlights the importance of screening the whole gene and regulatory regions when searching for novel variants associated with complex diseases, and the need to develop bioinformatics tools to predict the functional impact of non-coding variants and statistical tests which incorporate these predictions.

Intravenous Valproate versus Subcutaneous Sumatriptan in Acute Migraine Attack.

Migraine is a common and incapacitating neurologic disorder manifesting with episodic moderate to a severe headache and other symptoms such as photophobia, phonophobia, nausea, and vomiting. Triptans and ergot compounds have been used as treatment options for an acute migraine headache for many years. Triptans are considered the first line of treatment in patients with moderate to a severe migraine. Although the triptans are commonly used at any time during a migraine attack; they are more efficacious when used in the early stages of a migraine. Intravenous valproic acid has been shown to be well tolerated, safe, and with rapid onset of action in patients with acute moderate to severe and even refractory migraine. Sodium valproate is a Food and Drug Administration (FDA)-approved drug for prophylaxis of a migraine with and without aura. In this study, the main goal was to compare the effectiveness of sumatriptan versus valproate in an acute migraine. A randomized clinical trial including 37 patients with an acute migraine was considered to compare the effectiveness of sumatriptan versus valproate. The patients were divided into two groups. In first group, 6 mg subcutaneous of sumatriptan and in the second group 15 mg/Kg of valproate was administered. The outcomes including pain and drug adverse effects were compared across the groups. A total of 37 patients (7 male and 30 female) were evaluated in two groups. The difference between two groups regarding sex and age was not significant (P>0.05). The mean pain scores reduced from 8.3 to 4.7 and from 8.3 to 2.2 after one hour of treatment in sumatriptan and valproate groups, respectively. Response to treatment in valproate group was faster and more effective than sumatriptan group (P<0.05).The results indicated that valproate was more effective and with the faster response in patients with an acute migraine in comparison with sumatriptan without any recurrence and remarkable side effects.

Brief report: association of CCR1, KLRC4, IL12A-AS1, STAT4, and ERAP1 With Behçet's disease in Iranians.

OBJECTIVE: To independently replicate the top findings from 4 published genome-wide association studies (GWAS) of susceptibility genes in Behçet's disease (BD). METHODS: We tested 14 single-nucleotide polymorphisms (SNPs) in 13 genomic loci (excluding the major histocompatibility complex [MHC], IL10, and IL23R-IL12RB2, which have already been associated with BD in Iranians) for allelic and genotypic associations with BD in 973 patients and 828 controls from Iran and performed meta-analyses of the significantly associated markers. RESULTS: Six SNPs (in decreasing order of significance, rs7616215 located 38 kb downstream of CCR1, rs2617170 [p.Asn104Ser] in KLRC4, rs17810546 in IL12A-AS1, rs7574070 in STAT4, and rs10050860 [p.Asp575Asn] and rs13154629 in ERAP1) were nominally associated with BD in both allelic association tests (5.05 × 10(-9) ≤ Pallele ≤ 7.55 × 10(-3) ) and sex-adjusted genotypic association tests (6.01 × 10(-9) ≤ adjusted P value ≤ 1.30 × 10(-2) ). For all 6 SNPs tested by meta-analysis (Pmeta ), the association with BD was strengthened, because the direction and magnitude of association were similar across populations (e.g., for rs7574070, odds ratio [OR] for A allele 1.29 [95% confidence interval (95% CI) 1.21-1.37], Pmeta = 2.34 × 10(-16) ; for rs7616215, OR for C allele 0.70 [95% CI 0.65-0.76], Pmeta = 1.54 × 10(-19) ; for rs17810546, OR for A allele 0.60 [95% CI 0.52-0.70], Pmeta = 6.34 × 10(-11) ; for rs2617170, OR for T allele 0.76 [95% CI 0.70-0.81], Pmeta = 2.75 × 10(-14) ; for rs13154629, OR for TT genotype 2.76 [95% CI 2.01-3.80], Pmeta = 3.57 × 10(-10) ). CONCLUSION: This study reinforces the notion that CCR1, KLRC4, IL12A-AS1, STAT4, and ERAP1 are bona fide susceptibility genes for BD, in addition to the MHC, IL10, and IL23R-IL12RB2 loci. Future genetic and functional studies are now warranted to uncover the roles of these genes in the pathogenesis of BD.

Characterization of the major histocompatibility complex locus association with Behçet's disease in Iran.

INTRODUCTION: The aim of this study was to characterize the association of human leukocyte antigen (HLA) B alleles and major histocompatibility complex (MHC) single nucleotide polymorphisms (SNPs) with Behçet's disease (BD) in an Iranian dataset. METHODS: The association of three SNPs in the MHC region previously identified as the most associated in high-density genotyping studies was tested in a case-control study on 973 BD patients and 825 controls from Iran, and the association of HLA-B alleles was tested in a subset of 681 patients and 414 controls. RESULTS: We found that HLA-B*51 (P = 4.11 × 10(-41), OR [95% CI] = 4.63[3.66-5.85]) and B*15 confer risk for BD (P = 2.83 × 10(-2), OR [95% CI] = 1.75[1.08-2.84]) in Iranian, and in B*51 negative individuals, only the B*15 allele is significantly associated with BD (P = 2.51 × 10(-3), OR [95% CI] = 2.40[1.37-4.20]). rs76546355, formerly known as rs116799036, located between HLA-B and MICA (MHC class I polypeptide-related sequence A), demonstrated the same level of association with BD as HLA-B*51 (P adj = 1.78 × 10(-46), OR [95% CI] = 5.46[4.21-7.09], and P adj = 8.34 × 10(-48), OR [95% CI] = 5.44[4.20-7.05], respectively) in the HLA-B allelotyped subset, while rs2848713 was less associated (P adj = 7.14 × 10(-35), OR [95% CI] = 3.73[2.97-4.69]) and rs9260997 was not associated (P adj = 1.00 × 10(-1)). Additionally, we found that B*51 genotype-phenotype correlations do not survive Bonferroni correction, while carriers of the rs76546355 risk allele predominate in BD cases with genital ulcers, positive pathergy test and positive BD family history (2.31 × 10(-4) ≤ P ≤ 1.59 × 10(-3)). CONCLUSIONS: We found that the HLA-B*51 allele and the rs76546355/rs116799036 MHC SNP are independent genetic risk factors for BD in Iranian, and that positivity for the rs76546355/rs116799036 risk allele, but not for B*51, does correlate with specific demographic characteristics or clinical manifestations in BD patients.

Gene expression profiling and association studies implicate the neuregulin signaling pathway in Behçet's disease susceptibility.

Behçet's disease (BD) is a complex disease with genetic and environmental risk factors implicated in its etiology; however, its pathophysiology is poorly understood. To decipher BD's genetic underpinnings, we combined gene expression profiling with pathway analysis and association studies. We compared the gene expression profiles in peripheral blood mononuclear cells (PBMCs) of 15 patients and 14 matched controls using Affymetrix microarrays and found that the neuregulin signaling pathway was over-represented among the differentially expressed genes. The Epiregulin (EREG), Amphiregulin (AREG), and Neuregulin-1 (NRG1) genes of this pathway stand out as they are also among the top differentially expressed genes. Twelve haplotype tagging SNPs at the EREG-AREG locus and 15 SNPs in NRG1 found associated in at least one published BD genome-wide association study were tested for association with BD in a dataset of 976 Iranian patients and 839 controls. We found a novel association with BD for the rs6845297 SNP located downstream of EREG, and replicated three associations at NRG1 (rs4489285, rs383632, and rs1462891). Multifactor dimensionality reduction analysis indicated the existence of epistatic interactions between EREG and NRG1 variants. EREG-AREG and NRG1, which are members of the epidermal growth factor (EGF) family, seem to modulate BD susceptibility through main effects and gene-gene interactions. These association findings support a role for the EGF/ErbB signaling pathway in BD pathogenesis that warrants further investigation and highlight the importance of combining genetic and genomic approaches to dissect the genetic architecture of complex diseases.