SNPs in the promoter of a B cell-specific antisense transcript, SAS-ZFAT, determine susceptibility to autoimmune thyroid disease

Autoimmune thyroid disease (AITD) is caused by an immune response to self-thyroid antigens and has a significant genetic component. Antisense RNA transcripts have been implicated in gene regulation. Here we have identified a novel zinc-finger gene, designated ZFAT (zinc-finger gene in AITD susceptibility region), as one of the susceptibility genes in 8q23-q24 through an initial association analysis using the pro-bands in the previous linkage analysis and a subsequent association analysis of the samples from a total of 515 affected individuals and 526 controls. The T allele of the single-nucleotide polymorphism (SNP), Ex9b-SNP10 located in the intron 9 of ZFAT, is associated with increased risk for AITD (dominant model: odds ratio = 1.7, P = 0.000091). The Ex9b-SNP10 falls into the 3′-UTR of truncated-ZFAT(TR-ZFAT) and the promoter region of the small antisense transcript of ZFAT (SAS-ZFAT). In peripheral blood lymphocytes, SAS-ZFAT is exclusively expressed in CD19⁺ B cells and expression levels of SAS-ZFAT and TR-ZFAT seemed to correlate with the Ex9b-SNP10-T-associated ZFAT-allele, inversely and positively, respectively. The Ex9b-SNP10 is critically involved in the regulation of SAS-ZFAT expression in vitro and this expression results in a decreased expression of TR-ZFAT. These results suggested that the SNP-associated ZFAT-allele plays a critical role in B cell function by affecting the expression level of TR-ZFAT through regulating SAS-ZFAT expression and that this novel regulatory mechanism of SNPs might be involved in controlling susceptibility or resistance to human disease.