Altered IRF5 exon usage and increased expression of IRF7 targets in cells with an allele associated with risk for lupus (47.27)

Abstract

Abstract Background. The single nucleotide polymorphism rs2004640 within interferon regulatory factor 5 (IRF5) is a well established genetic risk locus for systemic lupus erythematosus (SLE). The overall effects on the cell, as well as the mechanisms through which this polymorphism enhances the risk for lupus remain elusive. Since an alternate first exon is created by this polymorphism, we hypothesized that the risk haplotype causes changes in splicing patterns. We further hypothesized that the risk allele may alter the expression levels of the transcriptional targets of either IRF5 or IRF7, which is modulated by IRF5. Methods. Peripheral blood mononuclear cells were isolated from lupus unaffected individuals after informed consent. DNA was extracted and genotyped for the allele at rs2004640. IRF 5 splice variant usage in EBV-transformed cells from nine race, sex, and age-matched pairs differing in rw2004640 genotype were compared using quantitative RT-PCR. Expression of genes regulated by IRF5 and IRF7 was also compared using quantitative RT-PCR. Statistical differences were evaluated using the Wilcoxon signed rank sum test. Results. Cells with the risk haplotype had more IRF5 mRNA (1.5-fold, p=0.05), but less exon 1C (1.9-fold, p=0.017) and less exon 1D (3.5-fold, p=0.012) than those with the protective type. Additionally, transcription of three targets of IRF7 was increased in risk cells, (average 1.5-fold increase, p<0.05).