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Arthritis Res Ther. 2010; 12(3): R115.
Published online Jun 10, 2010. doi:  10.1186/ar3051
PMCID: PMC2911908
Peptidyl arginine deiminase type IV (PADI4) haplotypes interact with shared epitope regardless of anti-cyclic citrullinated peptide antibody or erosive joint status in rheumatoid arthritis: a case control study
So-Young Bang,1 Tae-Un Han,2 Chan-Bum Choi,1 Yoon-Kyoung Sung,1 Sang-Cheol Bae,corresponding author1 and Changwon Kangcorresponding author2
1Department of Rheumatology, Hanyang University Hospital for Rheumatic Diseases, 17 Hangdang-dong Seongdong-gu, Seoul 133-792, South Korea
2Department of Biological Sciences, Korea Advanced Institute of Science and Technology, 335 Gwahangno Yuseong-gu, Daejeon 305-701, South Korea
corresponding authorCorresponding author.
So-Young Bang: byul2/at/hanmail.net; Tae-Un Han: fstcaptain/at/kaist.ac.kr; Chan-Bum Choi: cbchoi/at/hanyang.ac.kr; Yoon-Kyoung Sung: sungyk/at/hanyang.ac.kr; Sang-Cheol Bae: scbae/at/hanyang.ac.kr; Changwon Kang: ckang/at/kaist.ac.kr
Received March 23, 2010; Revised May 10, 2010; Accepted June 10, 2010.
Abstract
Introduction
Anti-cyclic citrullinated peptide autoantibodies (anti-CCP) are the most specific serologic marker for rheumatoid arthritis (RA). Genetic polymorphisms in a citrullinating (or deiminating) enzyme, peptidyl arginine deiminase type IV (PADI4) have been reproducibly associated with RA susceptibility in several populations. We investigated whether PADI4 polymorphisms contribute to anti-CCP-negative as well as -positive RA, whether they influence disease severity (erosive joint status), and whether they interact with two major risk factors for RA, Human Leukocyte Antigen-DRB1 (HLA-DRB1) shared epitope (SE) alleles and smoking, depending on anti-CCP and erosive joint status.
Methods
All 2,317 unrelated Korean subjects including 1,313 patients with RA and 1,004 unaffected controls were genotyped for three nonsynonymous (padi4_89, padi4_90, and padi4_92) and one synonymous (padi4_104) single-nucleotide polymorphisms (SNPs) in PADI4 and for HLA-DRB1 by direct DNA sequence analysis. Odds ratios (OR) were calculated by multivariate logistic regression. Interaction was evaluated by attributable proportions (AP), with 95% confidence intervals (CI).
Results
A functional haplotype of the three fully correlated nonsynonymous SNPs in PADI4 was significantly associated with susceptibility to not only anti-CCP-positive (adjusted OR 1.73, 95% CI 1.34 to 2.23) but also -negative RA (adjusted OR 1.75, 95% CI 1.15 to 2.68). A strong association with both non-erosive (adjusted OR 1.62, 95% CI 1.29 to 2.05) and erosive RA (adjusted OR 1.62, 95% CI 1.14 to 2.31) was observed for PADI4 haplotype. Gene-gene interactions between the homozygous RA-risk PADI4 haplotype and SE alleles were significant in both anti-CCP-positive (AP 0.45, 95% CI 0.20 to 0.71) and -negative RA (AP 0.61, 95% CI 0.29 to 0.92). Theses interactions were also observed for both non-erosive (AP 0.48, 95% CI 0.25 to 0.72) and erosive RA (AP 0.46, 95% CI 0.14 to 0.78). In contrast, no interaction was observed between smoking and PADI4 polymorphisms.
Conclusions
A haplotype of nonsynonymous SNPs in PADI4 contributes to development of RA regardless of anti-CCP or erosive joint status. The homozygous PADI4 haplotype contribution is affected by gene-gene interactions with HLA-DRB1 SE alleles.
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