Single-nucleotide polymorphisms in CD8A and their associations with T lymphocyte subpopulations in pig

Findings from previous studies suggested that the cluster of the differentiation 8 alpha (CD8A) gene plays a prominent role in human T lymphocyte subpopulations. However, the evidence from pig population is still rare. To determine whether the important role of the CD8A gene is conserved in pig, a candidate gene analysis was performed herein through genotype-phenotype associations. Five single-nucleotide polymorphisms (SNPs) locating in the regulatory region of porcine CD8A gene were detected and tested for association analysis with seven T lymphocyte subpopulations (proportion of CD4(-)CD8(-), CD4(+)CD8(+), CD4(+)CD8(-), CD4(-)CD8(+), CD4(+), CD8(+), and the ratio of CD4(+) to CD8(+) T cells in peripheral blood) in 382 Large White piglets. After Bonferroni correction for multiple testing, four SNPs were significantly associated with some or all of the seven T lymphocyte subpopulations. Analyses of pairwise D' measures of linkage disequilibrium between all SNPs were also explored. Two haplotype blocks was inferred and the association study on haplotype level revealed similar effects on T lymphocyte subpopulations. In addition, the tissue-specific RNA expression pattern and electrophoretic mobility shift assay offered further explanation of the link between the CD8A gene with porcine T lymphocyte subpopulations. The findings presented here provide strong evidence for associations of CD8A variants with T lymphocyte subpopulations and may be applied in porcine breeding programs.