Two-stage association study in Chinese Han identifies two independent associations in CCR1/CCR3 locus as candidate for Behcet's disease susceptibility

Previous GWAS studies from Turkey suggested a potential risk locus at CCR1/CCR3 for Behcet's disease. However, this locus did not reach the GWAS significance threshold and has not yet been examined in other ethnic populations. The current study aimed to explore whether this locus was associated with Behcet's disease in Chinese Han and the functional role of the identified variants. A two-stage association study was performed in 653 patients and 1,685 controls using the iPLEX system. Real-time PCR was performed to examine the expression level of CCR1 and CCR3 genes. Haplotype analysis was used to construct the haplotype block. Logistic regression analysis was applied to calculate the independence of multiple associations. Bonferroni correction was applied to account for multiple testing. First stage analysis showed that ten SNPs, located in 3'UTR, 5'UTR in CCR1 or 5'UTR in CCR3, were significantly associated with Behcet's disease (P (c) = 0.018 to 1.3 x 10(-3)). The associations of six SNPs within this locus are independent after control for the genetic effect of rs17282391 using logistic regression analysis. Haplotype analysis identified three associated haplotypes: H3 (GTGAC), H6 (CCATTA) and H9 (CGA) (P (c) = 0.04 to 7.79 x 10(-4)). Three SNPs rs13084057, rs13092160 and rs13075270 showed consistent association in replication and combining studies (replication P (c) = 5.31 x 10(-5) to 1.44 x 10(-5); combining P (c) = 2.76 x 10(-7) to 6.50 x 10(-8)). Interestingly, eQTLs database reveals that SNP rs13092160 is eQTLs SNP, suggesting that this SNP is likely to be functional SNP that directly affects gene expression. The expression of CCR1 and CCR3 was increased in individuals with the CT genotype of rs13092160 (P <0.05). No significant difference was found for the mRNA level of CCR1 and CCR3 between Behcet's patients and controls. These findings strongly indicate CCR1/CCR3 as a novel locus underlying Behcet's disease.