Human IL10 promoter haplotypes confer differential outcomes to experimental colitis in humanized BAC mice

Abstract

Abstract Most genetic variants associated with complex diseases map to non-coding regions of the genome, but determining their phenotypic consequences remains challenging. We devised a bacterial artificial chromosome (BAC) transgenic approach to model the effects of human non-coding single nucleotide polymorphisms (ncSNPs) on complex disease outcomes. As proof-of-concept, we focus on human IL10, a potent anti-inflammatory cytokine and key mediator of gut homeostasis. ncSNPs in the IL10 locus have been strongly associated with a variety of disease risks, including colitis susceptibility, but their biological functions are unclear. We created two genetically humanized IL10BAC transgenic mouse lines based on two common and well-defined −1082/−819/−592 IL10 promoter haplotypes (“ATA” and “GCC”) on a mouse Il10-deficient background. Although both IL10BAC strains were protected from spontaneous colitis, only ATA-bearing mice were resistant to dextran sulfate sodium (DSS)-induced acute colitis, while GCC and WT mice had high rates of morbidity and mortality. We found that ATAs had different kinetics of cell-type-specific IL-10 production pre- and post-DSS treatment compared to GCCs and WTs, which influenced the expression profiles of other cytokines and led to distinct immunophenotypes. The skewed responses culminated in the inability of GCCs and WTs to control DSS-induced bacteremia, resulting in death. Our data suggest that human IL10 ncSNPs impart allele-specific differences in spatiotemporal regulation of IL-10 expression, leading to differential outcomes to experimental colitis. Humanized BAC mice may serve as an important tool in modeling the potential impact of human non-coding variants on complex biological outcomes.