Forward genetic analysis of type I interferon responses to cytosolic deoxynucleotides reveals polymorphisms in Tmem173 gene of wild derived MOLF/EiJ mice. (P4201)

Abstract

Abstract We identified a novel phenotype in wild derived inbred mouse strain, MOLF/EiJ (MOLF). In response to cytosolic DNA or cyclic-diadenylate (c-di-AMP), MOLF macrophages exhibit high levels of IL-6 but very low levels of type I interferon, IFNβ, compared to classical inbred mouse strain C5BL/6J (B6). Furthermore, the IFNβ production is reduced in responses of MOLF macrophages to herpes simplex virus (HSV) and Listeria monocytogenes infection that release double stranded DNA and c-di-AMP into the cytosol, respectively. To identify loci that confer the trait, we used quantitative trait locus (QTL) mapping. We measured the IFNβ production of macrophages from a panel of 2nd filial generation (F2), B6/MOLF intercrossed mice, and genotyped the individual mice for inheritance of loci genome wide. The lack of IFNβ production mapped to a locus that contains Tmem173, a gene that encodes STING. STING is an innate immune cytosolic surveyor that mediates interferon response to cytosolic DNA and c-di-AMP. Sequencing the MOLF transcript of Tmem173 revealed multiple single nucleotide polymorphisms and an 18 base pair deletion in the MOLF allele of Tmem173. Almost all of these polymorphisms encode amino acid changes in the putative transmembrane domains of STING, while the cytosolic fraction is highly conserved. In vitro, expression of MOLF STING in Tmem173-/- murine embryonic fibroblasts (MEFs) shows greatly reduced activation of the IFNβ promoter, compared to C57BL/6.