Detection and Functional Evaluation of −262A/T and −188A/G Polymorphisms of SLAM Gene in Patients with Systemic Lupus Erythematosus

Abstract

Signaling lymphocytic activation molecule (SLAM) has been related to the pathology of systemic lupus erythematosus (SLE) through regulation of T cell-dependent humoral immune responses. We investigated the functional associations of the -262A/T and -188A/G polymorphisms of SLAM in Chinese patients with SLE. Genotyping of -262A/T (rs2295614) and -188A/G (rs2295613) in SLAM was carried out in 248 cases and 278 controls. Promoter activities of haplotypes on the SLAM gene were evaluated with the dual-luciferase reporter system. The mRNA expressions of SLAM on peripheral blood mononuclear cells (PBMC) of SLE patients with different genotypes were determined by real-time polymerase chain reaction. Frequencies of -262A allele and -188G allele were significantly higher in SLE patients than in controls. Haplotype analysis and multifactorial logistic regression analysis showed that individuals with the AG/AG haplotype had increased susceptibility to SLE (p = 0.002, OR 1.478, 95% CI 1.152-1.897). In response to PHA stimulation, the SLAM mRNA expression on PBMC of SLE patients was significantly higher in -262A-188G haplotype homozygotes compared with -262A-188G heterozygotes and individuals with other genotypes. Our findings suggest that -262A-188G haplotype in the SLAM gene promoter contributes to the risk of SLE by increasing the expression of SLAM.