Genomic Polymorphism in the Interferon-induced Helicase (IFIH1) Gene does not Confer Susceptibility to Autoimmune Thyroid Disease in the Japanese Population

Introduction

The pathogenesis of autoimmune thyroid diseases (AITDs), including Graves’ disease (GD) and Hashimoto's thyroiditis (HT) is thought to involve several risk factors, including genetic risk factors and environmental triggers such as cigarette smoking, iodine intake, and infection (reviewed in [1]). The first locus shown to be associated with AITDs was the HLA-DRB1 locus (reviewed in [1]). HLA-DR3 (DRB1*03) has been consistently shown to be associated with GD in Caucasians, with an odds ratio (OR) of 2.0–3.0 [1]. Other HLA alleles have been shown to be associated with GD in non-Caucasian populations (for a review see [2]). It was recently shown that arginine at position 74 of the DRβ1 chain (DRβ1-Arg74) is important for the development of GD in a significant proportion of patients [3] [4]. Non-HLA genes have also been shown to influence the expression of AITD. These genes include the genes for CTLA-4, CD40, thyroglobulin (Tg), and TSHR (reviewed in [1]).

A recent large-scale analysis of nonsynonymous coding single-nucleotide polymorphisms (SNPs) showed strong evidence that an alanine to threonine amino acid change at codon 946 of the interferon-induced helicase (IFIH1) gene (SNP ID rs1990760) was associated with type 1 diabetes (T1D) [5]. More recently, an association has also been reported between this SNP and GD in Caucasians [6]. These data indicate that the IFIH1 gene is a general autoimmunity gene, in addition to CTLA-4 and PTPN22 [1]. In the present study, we investigated whether IFIH1 gene polymorphism contributes to AITD susceptibility in the Japanese population.

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