A functional haplotype of PADI4 gene in rheumatoid arthritis: positive correlation in a french population

Abstract

Objective. A functional haplotype of peptidyl arginine deiminase 4 (PADI4) was associated with susceptibility to rheumatoid arthritis (RA) in Asian populations, but the results are contradictory in Europeans.We investigated (1) the association of 2 single-nucleotide polymorphisms (SNP) located in exon 2 of PADI4 with RA in another Caucasian population; and (2) the association between PADI4 and anti-citrullinated protein (anti-CCP) antibodies. Methods. DNA samples were obtained from 405 French RA patients and 275 controls. All RA patients met the revised criteria of the American College of Rheumatology. PADI4-89 163(G→A) and PADI4-90 245(T→C) SNP were genotyped using a PCR-RFLP method confirmed by direct sequencing. All patients and controls were genotyped for HLA-DRB1. The presence of anti-CCP antibodies was tested in 243 RA patients using an ELISA technique. Results. We focused on PADI4-89 163(G→A) and PADI4-90 245(T→C) SNP that distinguished 2 main haplotypes: AC haplotype (PADI4-89*A PADI4-90*C) and GT haplotype (PADI4-89*G PADI4-90*T), described, respectively, as "nonsusceptible" and "susceptible." A positive association between RA and presence of the GT haplotype was found in the heterozygous state (p = 0.002) and the homozygous state (RA patients 22%, controls 13%; p = 0.005). A correlation was observed between the presence but not the level of anti-CCP antibodies and the GT heterozygous (p = 0.03) and homozygous (p = 0.05) haplotypes. No correlation was found between the HLA-DRB1 shared epitope and any of the PADI4 haplotypes. Conclusion. Our findings confirm those of Japanese, Korean, and Canadian studies and suggest that PADI4 may be a new susceptibility gene independent of HLA-DRB1 for RA in Caucasian populations. The Journal of Rheumatology Copyright © 2009. All rights reserved.