Association Of ERAP1, ANTXR2, IL1R2, IL23R, JAK2 And STAT3 Polymorphisms With Ankylosing Spondylitis

Background:Ankylosing spondylitis (AS) is a common autoimmune disease that often disables the patients due to severe pain or deformity of axial skeleton and/or peripheral joints. The incidence of AS was estimated to be 0.1%-0.9% worldwide and 0.3% in China. The susceptibility of AS is strongly determined by genetic predisposition with the heritability over 90%. Human leukocyte antigen-B27 (HLA-B27) is most commonly known to be associated with the inheritance of AS. However, although HLA-B27 is present in 95% of AS patients, only 1%-5% of the HLA-B27 positive general population develops AS, and its contribution to overall genetic predisposition is only 16-40%. Moreover, twin studies and familial studies indicated that non major histocompatibility complex (MHC) gene contributed 60%-70% to the total genetic risk. Sibling recurrence risk ratio (λs) for HLA-B27 is 5-6, whereas that for non-MHC is about at 14. All of these results suggested that non-MHC gene played an important role in the susceptibility of AS. Recently, the single nucleotide polymorphisms (SNP) of endoplasmic reticulum aminopeptidase-1 (ERAP1), anthrax toxin receptor 2 (ANTXR2), interleukin 1 receptor type 2 (IL1R2) and IL23 receptor (IL23R) were found to be highly associated with AS in Caucasian population. Verification of these associations in multiple races is necessary for further exploring the role of the genes and understanding the pathogenesis of AS.The clinical and pathological manifestations of AS are closely related to the unbalance of immunologic functions. The role of IL23/Th17/IL17 axis in AS has gained more and more attentions in recent years. IL17, a strong proinflammatory cytokine produced by Th17 cells, is the core factor and the direct contributor of inflammatory effect generated by IL23/Thl7/IL17 axis. Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3) are key elements that regulate the differentiation of naive T cells into Th17 cells. In addition, JAK2 also belong to a gene network referred to as "IL23 pathway". JAK2 and STAT3 polymorphisms have recently been demonstrated to be associated with inflammatory bowel disease (IBD), a condition which might share common pathogenesis and genetic factors with AS. Therefore, we hypothesized that polymorphisms of JAK2 and STAT3 may also be associated with AS.The present study aimed to investigate the associations between ERAP1, ANTXR2, IL1R2, IL23R and AS in Chinese Han population, and identify whether JAK2 and STAT3 variants are associated with the susceptibility of AS. The study is divided into the following two parts.PartⅠ:Association of ERAP1, ANTXR2, IL1R2 and IL23R polymorphisms with AS in Chinese Han populationObjective:To investigate the association of ERAP1, ANTXR2, IL1R2 and IL23R variants with the susceptibility of AS in Chinese Han population.Materials and methods:200 AS patients satisfied the modified New York criteria were recruited from clinic and hospitalized patients.200 controls were matched by age and sex. All patients were of Chinese Han origin.2ml peripheral venous blood was collected with sample tube containing anticoagulant from each participant. DNA was extracted and purified using the AxyPrep Blood Genomic DNA Miniprep kit. Genotyping of each subject for 14 SNPs was performed by MassArray compact analyzer based on the chip-based matrix-assisted laser desorption ionization time-of-flight mass spectrometry platform. These 14 SNPs were shown to be associated with AS in Causasian population. The odds ratio and 95%confidence intervals of allele and genotype frequency were obtained with Plink software. Haplotype analysis was finished with use of Haploview software version 4.1.Results:No significant difference of the distribution of 14 SNPs in case group versus control group was observed. Strikingly, rs 11209026 was found not to be polymorphic in all subjects. Conclusion:ERAP1, ANTXR2, IL1R2 and IL23R polymorphisms are not associated with the susceptibility of AS in Chinese Han population. Our results were markedly discordant with that of Caucasian populations. These findings further proved that differences did exist on the genetic background and predisposing genes of the same disease in different races and also suggested that population stratification should strictly considered when designing the genetic study for complex multigenetic disease.PartⅡ:Association of the variants of JAK2 and STAT3 with the susceptibility of ASObjective:To identify the association of JAK2 and STAT3 with the susceptibility of ASMaterials and methods:200 AS patients satisfied the modified New York criteria and 200 controls were included.10 SNPs were tested by MALDI-TOF genotyping technology.7 of these 10 sites were tag SNPs chosen based on pairwise r2 method using SNP Brower 3.5 software with the parameter set at r2<0.85 and minor allelic frequency (MAF)>0.3, another 3 SNPs were loci that were reported to be associated with IBD in recent literatures. Haploview 4.1 was used to analyze the haplotype. Plink was utilized to analyze the distributions of polymorphisms and haplotypes, as well as the odds ratio and 95% confidence intervals between cases and controls.Results:There is no significant difference of the distribution of 10 SNPs and genotypes in case group vs control group. Haplotype analysis showed the distribution of the haplotype rs1536798/rs10119004/rs7857730-CGT in JAK2 locus was statistically different between AS patients and healthy controls (P=0.0323).Conclusion:JAK2 variants are associated with the susceptibility of AS. Although IL23R is not related to AS in Chinese Han population, the association of JAK2 with AS still demonstrated the importance of IL23 pathway in the pathogenesis of AS based on the fact that JAK2 belong to the "IL23 pathway". Our finding also provided further evidences for the close relationship between AS and IBD.