TRPM2 SNP genotype previously associated with susceptibility to Rhodococcus equi pneumonia in Quarter Horse foals displays differential gene expression identified using RNA-Seq

BACKGROUND: Rhodococcus equi (R. equi) is an intracellular bacterium that affects young foals and immuno-compromised individuals causing severe pneumonia. Currently, the genetic mechanisms that confer susceptibility and/or resistance to R. equi are not fully understood. Previously, using a SNP-based genome-wide association study, we identified a region on equine chromosome 26 associated with culture-confirmed clinical pneumonia. To better characterize this region and understand the function of the SNP located within TRPM2 that was associated with R. equi pneumonia, we performed RNA-Seq on 12 horses representing the 3 genotypic forms of this SNP. RESULTS: We identified differentially expressed genes in the innate immune response pathway when comparing homozygous A allele horses with the AB and BB horses. Isoform analyses of the RNA-Seq data predicted the existence of multiple transcripts and provided evidence of differential expression at the TRPM2 locus. This finding is consistent with previously demonstrated work in human cell lines in which isoform-specific expression of TRPM2 was critical for cell viability. CONCLUSIONS: This work demonstrates that SNPs in TRPM2 are associated with differences in gene expression, suggesting that modulation of expression of this innate immune gene contributes to susceptibility to R. equi pneumonia.