Association Of Toll Like Receptor 7 Gene Copy Number Variations And Ankylosing Spondylitis In A Chinese Han Population

Objective: To analyze the the relationship between TLR7 gene Copy Number variation?Copy Number variation,CNVs?and the susceptibility and severity of disease,and the possible interactions between TLR7 gene CNVs and environmental factors.Methods: In 2013-2016,we collected the case group from the department of rheumatology and immunology at the First Affiliated Hospital of Anhui Medical University.At the same time,we collected the control group in the central blood station of Hefei.Case group and control group should be matched according to the principle of age and gender.Both case group and control group needed to provide 5 ml peripheral blood,questionnaire was finished with the help of our team in order to collect data accurately.Firstly,DNA extraction was carried out and the extraction method was based on the DNA kit?QIAGEN?,and then the copy number detection was carried out by Accu CopyTM method.According to the analysis purpose and data type,the corresponding statistical analysis method was adopted.Continuous data with normalized distribution were presented as mean±SD,and non-normalized continuous data were shown as median?P25,P75?.Qualitative data is described directly by frequency and percentage.The comparison of quantitative data between the case group and the control group was carried out by t test,and the comparison of qualitative data and the frequency distribution of the gene copy number were conducted by chi square test.The relationship between CNVs and disease severity and susceptibility were analyzed.In addition,case-only study was used to analyze the interaction between CNVs and environmental factors.P value <0.05 was deceted as significant.However,Bonferroni correction was applied when we conducted mulitiple comparisions.Results: The basic characteristics were as follows: There were 649 AS patients in the case group,and the sex ratio of men and women was 5.01:1,with an average age of 27.83± 7.58 years old;We have recurited 628 controls who were28.33±8.93 years old,with the sex ratio 4.74:1.The statistical test indicated that there was no significant difference between the two groups in age?t=-1.060,P=0.289?and gender??2=0.136,P=0.712?.The distribution of TLR7 gene copy number in the case group and control group: TLR7₁ gene fragment: in patients with AS,there were 522 cases?83.1%?of 1 copy and 106 cases?16.9%?of 2 copies.In the comparision group,456 cases?77.2%?carried one copy and 135 cases?22.8%?carried 2 copies.The difference in the distribution of TLR7₁ gene copies between the two groups was statistically significant??2=6.827,P=0.009?.TLR7₂ gene fragment: in patients with AS,there were 523 cases?83.1%?of 1 copy and 106 cases?16.9%?of 2 copies.In the comparision group,459 cases?77.1%?carried 1 copy and 135 cases?22.9%?carried 2 copies.The frequency distribution of TLR7₂ gene copies was statistically significant between the two groups??2=6.665,P=0.010?.TLR7 gene CNVs and the AS genetic susceptibility analysis: lower copy number conferred the risk of AS?TLR7₁: OR=2.066,95%CI:1.318³.238,P=0.002;TLR7₂: OR=2.061,95%CI: 1.315³.230,P=0.002?.After stratification by gender: the low copy number of TLR7 gene was the risk factor for male AS?TLR7₁: OR=8.036,95%CI: 3.774¹7.107,P<0.001;TLR7₂: OR=8.019,95%CI: 3.767¹7.072,P<0.001?;However,in females,the lower copy number of TLR7 gene was the protective factor of AS?TLR7₁: OR=0.221,95%CI: 0.085⁰.572,P=0.002;TLR7₂: OR=0.221,95%CI: 0.085⁰.572,P=0.002?.The analysis between TLR7 gene CNVs and the severity of disease: we found TLR7 gene CNVs were not associated with BASDAI and BASFI.In other words,TLR7 gene CNVs would not influence disease progression.The interaction analysis between TLR7 gene CNVs and environmental factors: Logistic regression analysis in the case-only study of CNVs-environment interaction indicated that oil type might interact with TLR7 gene CNVs in male AS patients?TLR7₁: OR=9.561,95%CI: 1.058⁸6.408,P=0.044;TLR7₂: OR=9.672,95%CI: 1.070⁸7.417,P=0.043?.Conclusion: TLR7 gene CNVs might be related to AS susceptibility,and lower copy number?=1?in males may be a risk factor for AS,while lower copy number?=1?in females may be the protective factor of AS.TLR7 gene CNVs was not associated with the severity of AS.In male patients,oil type might interact with TLR7 gene CNVs.