PADI4 gene polymorphism is not associated with ankylosing spondylitis in Chinese Han population

The cause of ankylosing spondylitis (AS) remains unelucidated. Both genetic and environmental factors are suspected playing an important role in AS development. Peptidyl arginine deiminase type IV (PADI4) is a member of gene family that encodes enzymes responsible for the conversion of arginine to citrulline residues. A strong linkage between PADI4 polymorphism and rheumatoid arthritis has been found in Japanese and Korean patients, but there is no association study about PADI4 in AS. We speculated that PADI4 may be a pivotal gene for AS development. So we investigated the PADI4 polymorphisms in AS in Chinese Han population. A total of 316 Chinese AS patients of Han nationality and 439 healthy controls were recruited. Five single-nucleotide polymorphisms (SNP), PADI4-89 (rs11203366), PADI4-90 (rs11203367), PADI4-92 (rs874881) PADI4-94 (rs2240340) and PADI4-104 (rs1748033), of PADI4 gene were selected, and the major allele frequencies between cases and controls were assessed as 0.571 versus 0.597, 0.565 versus 0.585, 0.565 versus 0.574, 0.446 versus 0.421 and 0.614 versus 620, respectively. No significant differences in the frequency of PADI4 alleles and genotypes between the cases and controls were observed. Two haplotypes ACGGC and GTCGC were significant with AS even after Bonferroni's correction but were with a tiny frequency in AS cases as 1.0% and 1.2%, respectively. These results indicate that PADI4 polymorphisms may not play an important role in the development of AS in Chinese Han population.