Autoimmune rheumatologic diseases
Genome-wide association studies have identified more than 40 loci that may be pathologically relevant for systemic lupus erythematosus (SLE). Variants in STAT4, are robustly associated with lupus nephritis (LN). Although these variants have been shown to increase STAT4 expression in peripheral blood mononuclear cells and monocytes, the molecular mechanisms that underlie this effect and its functional consequences are still unclear.
Naïve CD4 T cells obtained from healthy human donors homozygous for the protective (Prot) or risk (Risk) STAT4 alleles, were cultured in Th1 polarizing conditions. Cells carrying the Prot alleles, downregulated STAT4 transcription in response to sustained exposure to IL-12. In contrast, cells with the Risk alleles did not modulate STAT4 and consequently accumulated increased amounts of the transcription factor. This was accompanied by increased levels of STAT4 protein and pSTAT4. Further, Risk cells produced significantly more IFN-γ. To dissect the regulatory effects of the SLE-associated variants, we edited Jurkat cells using CRISPR/Cas9 technology. Disruption of the STAT4 intronic region that contains the SLE-associated SNPs unleashed the production of IFN-γ. The effect of STAT4 overexpression was evaluated in vivo by comparing the pathogenic capacity of STAT4-overexpressing and control OT-I cells. Upon transfer to RIP-mOVA mice, STAT4-OT-I cells exhibited increased migration into the pancreas and established insular inflammatory infiltrates.