Association of mineralization-related genes TNAP and ANKH polymorphisms with ankylosing spondylitis in the Chinese Han population

The aim of this study was to investigate two mineralization-related genes TNAP and ANKH polymorphisms associated with ankylosing spondylitis (AS) in the North Chinese Han population. We carried out a case-control study in Chinese AS cohorts involving 278 AS patients and 286 unrelated healthy controls. Five TNAP SNPs (rs3200254, rs1256348, rs1472563, rs1780329, rs3767155) and four ANKH SNPs (rs25957, rs26307, rs27356, rs28006) were genotyped by the Multiplex Snapshot method. There were significant differences in genotype (permutated p = 0.00481) and allele (permutated p = 0.0126) frequencies of the rs26307 ANKH SNP between AS patients and controls. Logistic regression analysis suggested an association of AS with the polymorphism in an additive model (OR = 0.640, 95%CI = 0.480-0.853, p = 0.0023, permutation 10,000 corrected p = 0.0158) and a dominant model (OR = 0.599, 95%CI = 0.423-0.846, p = 0.0037, permutation 10,000 corrected p = 0.022). Haplotype analysis identified the ANKH haplotype rs26307(C)/rs27356 (T) as a predisposing factor for AS (OR = 1.53, 95%CI = 1.165-2.071, p = 0.0026, permutation 10,000 corrected p = 0.0103). This study provides evidence that variation in the ANKH gene influences susceptibility to AS in the Northern Han Chinese population.