A functional polymorphism in the TIM-1 gene is associated with asthma in a Chinese Han population

Background: TIM-1, a member of the T cell immunoglobulin and mucin domain (TIM) gene family was implicated as an asthma susceptibility gene in previous studies. TIM-1 is selectively expressed on activated CD4+ T cells and its expression is sustained preferentially on T helper type 2 (Th2) cells, which suggests that TIM-1 is associated with T cell differentiation and the development of Th2-biased immune response. Methods: In order to evaluate the effects of the promoter polymorphism in the TIM-1 gene on asthma susceptibility in a Chinese Han population, 2 promoter polymorphisms, -416G > C and -1454G > A, from 2 alternative promoter regions, were genotyped in 409 unrelated asthma patients and 305 healthy controls by using polymerase chain reaction and restriction fragment length polymorphism. Also, we analyzed the functional significance of -416G > C using the luciferase reporter gene assay. Results: We found that -416G > C was associated with asthma susceptibility in our study population ( chi(2) = 9.88, p = 0.002, odds ratio 1.41, 95% confidence interval 1.14-1.75). No statistically significant difference in the distribution of genotype and allele frequency of the -1454G > A site was observed. The -416G > C substitution increased the transcriptional activity of the TIM-1 gene. Conclusion: Our findings suggest that the -416G > C variation site in the human TIM-1 promoter region is associated with asthma susceptibility in a Chinese Han population.