Association Of FCRL3 Gene Polymorphisms With Behcet's Disease In A Chinese Population

Purpose:Beh?et's disease (BD) is an idiopathic, multisystem and recurrent chronic inflammatory disease in China. The major clinical manifestations include recurrent oral and genital ulceration, uveitis and erythema nodosum. BD exists worldwide and has significant regional differences. It is quite common along the ancient'Silk Route'countries extending from China to the Mediterranean area. BD is one of the most common uveitis entities in China. Although the precise etiology of BD remains unknown, extensive studies suggest that autoimmunity and genetic factors are involved in its pathogenesis.As a new immunemodulation gene, FCRL3 may play an important role in autoimmunity and autoimmune diseases. Recently, a classical study by Kochi et al. in Japan found that four SNPs of the FCRL3 gene (-169C/T, -110A/G, +358C/G and +1381A/G ) were associated with rheumatoid arthritis (RA) and that SNP -169C/T was associated with autoimmune thyroid disease and systemic lupus erythematosus (SLE). As various autoimmune disorders may share common pathogenic pathways, genes that have been found to be involved in one autoimmune disease may also be considered as a candidate associated with other autoimmune diseases. Until now FCRL3 gene polymorphism has not yet been investigated in BD. In this study, we analyzed the association of four SNPs, i.e. -169C/T, -110A/G, +358C/G and +1381A/G, of the FCRL3 gene with susceptibility for BD in a Chinese population, and the association stratified by HLA-B51, clinical parameters and gender. MethodsStudy participantsPatients and controls were recruited from the Zhongshan Ophthalmic Center of Sun Yat-sen University and the First Affiliated Hospital of Chongqing Medical University in China. The test subjects consisted of 245 Chinese BD patients (aged 28.6±6.0 years ) and 289 healthy controls (aged 34.2±10.0 years).The diagnosis of Behcet's disease followed the criteria of the International Study Group for Behcet's disease. All subjects gave their written informed consent for this study, and the study protocol was approved by the local institutional ethics committee.SNPs and genotyping DNA was prepared by proteinase K digestion and salt extraction from peripheral blood of patients and controls, and stored at -20℃until use. The four SNPs in the FCRL3 gene, namely -169C/T , -110G/A, +358 C/G and +1381A/G, were genotyped by PCR restriction fragment length polymorphism (PCR-RFLP) .HLA-B51 genotyping was performed by the PCR-sequence specific primers( PCR-SSP ) method as described previously.Statistical analysisStatistical analysis was performed with the SPSS version 12.0 for Windows. Hardy-Weinberg Equilibrium (HWE) was tested by theχ~2 test. We evaluated the frequency of genotypes and alleles in this study using theχ~2 test or Fisher's exact test. The haplotype frequency and Linkage disequilibrium (LD) of the SNPs were estimated with the Haploview 3.2 program. All the data were corrected by Bonferroni correction.ResultsFour SNPs in the FCRL3 gene were determined in 245 BD patients and 289 healthy controls. The results showed that all the cases and controls were in HWE. The frequency of the G allele at the -110 site was significantly higher in patients (75.2%) than in controls (67.5%) (corrected p(pc)=0.044,χ~2=7.72 ). The -110 GG genotype was also found to be increased in patients (P=0.007), but this significance was lost after Bonferroni correction (pc =0.084). The frequency of the -169C:-110G: +358C: +1381G haplotype was significantly higher in patients as compared with controls (pc =0.0096,χ~2=11.70). The frequency of haplotype -169T: -110A: +358C: +1381G was significantly lower in patients than that in controls (pc =0.032,χ~2=9.27). No significant difference was observed in the distribution of other alleles and genotypes between BD patients and controls in the remaining three SNPs tested.As the HLA-B51 gene has been shown to be strongly associated with BD, we further analyzed its frequency in patients and controls. Stratification analysis according to HLA-B51 showed no significant difference between BD patients and healthy controls. Similar negative results were found in clinical characteristics and gender stratification.Conclusion:Our study revealed that the -110G allele and haplotype CGCG are positively associated and haplotype TACG is negatively associated with the susceptibility to BD.