Association of TLR7 gene copy number variations with ankylosing spondylitis in a Chinese population: a case control study

Objectives: To explore the association of TLR7 gene copy number variations (CNVs) with the susceptibility of ankylosing spondylitis (AS).

Methods: The case control study was performed in 649 Chinese Han patients with AS and 628 healthy controls. The copy numbers of TLR7 gene (2 fragments) were measured by AccuCopy^TM methods. Chi-square and logistic regression models were performed to investigate the association of TLR7 gene CNVs with AS. Odds ratio (ORs) and 95% confidence intervals (CIs) was calculated to estimate AS risk and the Bonferroni correction was applied owing to multiple testing.

Results: The logistic regression analysis showed that one copy was significantly associated with AS susceptibility after Bonferroni correction (for the TLR7_1 fragment: OR=1.458, 95%CI(1.098,1.936), p=0.009; for the TLR7_2 fragment: OR=1.451, 95%CI (1.093,1.927), p=0.010), and this association still exists after adjustment of age and sex (for the TLR7_1 fragment: adjusted OR=2.066, 95%CI (1.318,3.238), p=0.002; for the TLR7_2 fragment: adjusted OR=2.061, 95%CI (1.315,3.230), p=0.002). However, logistic regression analysis stratified by gender showed a higher OR in males (for the TLR7_1 fragment: OR(95%CI)=7.987(3.756,16.983); for the TLR7_2 fragment: OR(95%CI)=7.947(3.738,16.897)) than in females (for the TLR7_1 fragment: OR(95%CI)=0.204(0.080,0.524); for the TLR7_2 fragment: OR(95%CI)=0.204(0.080,0.524)).

Conclusions: We conclude that the lower copy number (=1) of TLR7 gene confers a risk factor for AS susceptibility in males but protective factor in females.