Association of beta-defensin gene copy number variations with ankylosing spondylitis in Chinese population: A case-control study

Objectives. To explore the association of -defensin gene copy number variations (CNVs) with ankylosing spondylitis (AS).Methods. In this study, 405 unrelated Chinese Han patients with AS and 401 unrelated healthy controls were enrolled. The copy numbers of DEFB4 gene (2 fragments) were measured by AccuCopy methods. The association of DEFB4 gene CNVs with AS susceptibility was analyzed by chi-square and logistic regression models. Besides, P values, odds ratio, and 95% confidence intervals (CIs) were used to estimate the effects of risk.Results. The range of DEFB4_1 CN was 0-7 and the range of DEFB4_2 CN was 1-8 both in patients and controls. P values of (2) trend test for the association of DEFB4_1 and DEFB4_2 with AS were 0.607 and 0.005, respectively. The results of DEFB4_2, compared with the individual having median 3 copies, those carrying 2-copies [OR = 0.68, 95%CI: (0.46, 0.99), P = 0.049; adjusted OR = 0.69, 95%CI(0.47, 1.03), P = 0.067.]; and those carrying 4-copies [OR = 0.62, 95%CI: (0.45, 0.86), P = 0.004; adjusted OR = 0.64, 95%CI: (0.46, 0.88), P = 0.006], were significantly associated with decreasing risk of AS. Univariate analysis showed that both DEFB4_1 and DEFB4_2 were associated with Bath AS Disease Activity Index or BASDAI. After adjusted by age, sex, and disease duration, the results changed little, which demonstrated that high copies may be linked with decrease in the risk of disease severity [OR = 0.71, 95%CI: (0.56, 0.90), P = 0.005; OR = 0.75, 95%CI: (0.60, 0.94), P = 0.013, respectively].Conclusions. The CNs of DEFB4 gene may be associated with AS and involved in disease progression.