The gene encoding interferon (IFN)-γ, IFNG, is known as one of the candidate susceptibility genes for type 1 diabetes. In addition, cytokines, including IFN-γ, play important roles in the pathogenesis of type 1 diabetes. Therefore, we focused on the Th1-specific T-box transcription factor gene (T-bet), which contributes to the induction of the hallmark Th1 cytokine, IFN-γ. We first screened for polymorphisms in the T-bet gene and detected two microsatellite repeat polymorphisms located in intron 1 and the 3′- flanking region, and two single nucleotide polymorphisms, including a His33Gln substitution within the coding region. By association studies, the Gln-positive phenotype and (CA)14 allele in 3′-flanking region of T-bet were found to be associated with type 1 diabetes in the Japanese population. Furthermore, Gln33 T-bet showed a significantly higher transcriptional activity of the IFNG gene via a dual luciferase reporter assay. Our study suggests the first evidence of an association between type 1 diabetes and polymorphisms in the T-bet gene, and that variation in T-bet transcriptional activity may play a role in the development of type 1 diabetes, possibly through the effect on IFN-γ production in Th1 cells.
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