Characterization of BSA, A Bovine Class I MHC Sequence

Abstract

The class I MHC region in the vertebrate genome contains genes for receptor proteins that present cytosolic antigens to lymphocytes in the initial phase of the immune response. Most cattle express a class I gene called “BSA” as the most prevalent mRNA transcript in leukocytes. However, sequence corresponding to BSA is missing from the bovine reference genome sequence and from genomic libraries prepared from several different cattle. We used locus specific primers to amplify the BSA gene in the DNA from L1 Domino, the donor for the CHORI240 BAC library and from each of the donors for two other genomic libraries. Additionally, we characterize the sequence variation of BSA among 92 representative BoLA haplotypes, including an evolutionary-conserved, trans-species frameshift polymorphism in cattle and bison. Variation at the BSA locus should be included in the design of SNP arrays and alignments to reference genomes for the identification of BoLA-associated phenotypes in genome wide association studies (GWAS).