Analysis of 47 Non-MHC Ankylosing Spondylitis Susceptibility Loci Regarding Associated Variants across Whites and Han Chinese

Association of Endoplasmic Reticulum Aminopeptidase 1 Gene Polymorphism with Susceptibility and Severity of Axial Spondyloarthritis in Egyptian Population: A Single-center Case-Control Study

BACKGROUND

Axial spondyloarthritis (axSpA) is a systemic, progressive, autoimmune disease. Complex interactions between environmental factors and host immune responses are the origin of axSpA. Together with human leukocyte antigen (HLA-B27), endoplasmic reticulum aminopeptidase 1 (ERAP1) gene is a potential non-HLA contributor to axSpA susceptibility.

AIM

This study aimed to identify the role of ERAP1 single-nucleotide polymorphisms (SNPs) (rs30187, rs27044, and rs27037) in susceptibility to and severity of axSpA in Egyptian patients.

METHODS

In this case-control study, we enrolled 120 patients with axSpA and 120 healthy individuals as controls. Real-time polymerase chain reaction was used to identify ERAP1 polymorphisms.

RESULTS

The present study revealed no significant association between ERAP1 SNPs (rs30187, rs27044, and rs27037) and axSpA susceptibility in Egyptian patients. A significant relationship was found only between the ERAP1 SNP rs27037 "GT" genotype and axSpA HLA-B27-positive cases, demonstrating a functional interaction between ERAP1 and HLA-B27-positive cases. Our analysis revealed a significant association between the ERAP1 SNP rs27037 "GT and TT" genotypes and Bath Ankylosing Spondylitis Disease Activity Index, in addition to an association between the ERAP1 SNP rs27037 "TT" genotype and active enthesitis. The ERAP1 SNP rs27044 "GG" genotype was significantly associated with active enthesitis, but not with clinical axial involvement. Finally, we did not observe a significant relationship between HLA-B27 positivity and disease severity in the studied cases.

CONCLUSION

Three SNPs (rs30187, rs27044, and rs27037) in ERAP1 do not confer susceptibility to axSpA in Egyptian patients. This association existed exclusively between the ERAP1 SNP (rs27037) "GT" genotype and axSpA HLA-B27-positive cases.

Shedding Light on the Role of ERAP1 in Axial Spondyloarthritis

Spondyloarthritis (SpA) is a multifactorial chronic inflammatory disease affecting the axial skeleton (axSpA) and/or peripheral joints (p-SpA) and entheses. The disease's pathogenesis depends on genetic, immunological, mechanical, and environmental factors. Endoplasmic reticulum aminopeptidase 1 (ERAP1) is a multifunctional enzyme that shapes the peptide repertoire presented by major histocompatibility complex (MHC) class I molecules. Genome-wide association studies (GWAS) have identified different single nucleotide polymorphisms (SNPs) in ERAP1 that are associated with several autoimmune diseases, including axSpA. Therefore, a deeper understanding of the ERAP1 role in axSpA could make it a potential therapeutic target for this disease and offer greater insight into its impact on the immune system. Here, we review the biological functions and structure of ERAP1, discuss ERAP1 polymorphisms and their association with axSpA, highlight the interaction between ERAP1 and human leukocyte antigen (HLA)-B27, and review the association between ERAP1 SNPs and axSpA clinical parameters.

Genome-wide association study reveals ethnicity-specific SNPs associated with ankylosing spondylitis in the Taiwanese population

BACKGROUND

Ankylosing spondylitis (AS) is an autoimmune disease affecting mainly spine and sacroiliac joints and adjacent soft tissues. Genome-wide association studies (GWASs) are used to evaluate genetic associations and to predict genetic risk factors that determine the biological basis of disease susceptibility. We aimed to explore the race-specific SNP susceptibility of AS in Taiwanese individuals and to investigate the association between HLA-B27 and AS susceptibility SNPs in Taiwan.

METHODS

Genotyping data were collected from a medical center participating in the Taiwan Precision Medicine Initiative (TPMI) in the northern district of Taiwan. We designed a case-control study to identify AS susceptibility SNPs through GWAS. We searched the genome browser to find the corresponding susceptibility genes and used the GTEx database to confirm the regulation of gene expression. A polygenic risk score approach was also applied to evaluate the genetic variants in the prediction of developing AS.

RESULTS

The results showed that the SNPs located on the sixth chromosome were related to higher susceptibility in the AS group. There was no overlap between our results and the susceptibility SNPs found in other races. The 12 tag SNPs located in the MHC region that were found through the linkage disequilibrium method had higher gene expression. Furthermore, Taiwanese people with HLA-B27 positivity had a higher proportion of minor alleles. This might be the reason that the AS prevalence is higher in Taiwan than in other countries. We developed AS polygenic risk score models with six different methods in which those with the top 10% polygenic risk had a fivefold increased risk of developing AS compared to the remaining group with low risk.

CONCLUSION

A total of 147 SNPs in the Taiwanese population were found to be statistically significantly associated with AS on the sixth pair of chromosomes and did not overlap with previously published sites in the GWAS Catalog. Whether those genes mapped by AS-associated SNPs are involved in AS and what the pathogenic mechanism of the mapped genes is remain to be further studied.

Associations between ERAP1 polymorphisms and ankylosing spondylitis susceptibility in HLA-B27 positive population: a Meta-analysis and bioinformatics analysis

Human leukocyte antigen (HLA)-B27 confers a key role in ankylosing spondylitis (AS) susceptibility. Endoplasmic reticulum aminopeptidase 1 (ERAP1) polymorphisms are associated with AS susceptibility in common population. In this study we intended to evaluate the possible association between ERAP1 polymorphisms and AS susceptibility in HLA-27 positive population. Data were collected from Pubmed, Embase, and Cochrane databases. The pooled odds ratios and 95% confidence intervals of the minor allele of each locus were calculated to appraise the associations under ERAP1 polymorphisms and AS in HLA-B27 positive population. Bioinformatics analysis was performed to explore the underlying mechanism. Four studies were included in this meta-analysis. There was a significant association between the minor allele of rs2287987 and reducing the risk of developing AS in HLA-B27 positive population. But there was no significant association between the minor allele of rs30187, rs27044, rs10050860 and rs17482078 and AS susceptibility. According to HaploReg, 5 motifs changed for rs2287987 were found. The eQTL analysis demonstrated that rs2287987 may influence ERAP1 expression. Rs2287987 in ERAP1 may have small influence on AS susceptibility in HLA-B27 positive population. Bioinformatics analysis indicated that the altered motifs and the change of EARP1 expression may influence the AS susceptibility.