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Diversity of the MHC class II DRB alleles in chamois populations

The genes of the major histocompatibility complex (MHC) code for receptors that recognize and bind antigens in order to present them to T cells, thus they have a major role in determining the immune response. MHC region includes some of the most variable loci in the vertebrate genome, reflecting the strong association between MHC diversity and resistance/susceptibility to disease. With their well-characterized function and exceptional diversity, they are a key genetic marker for studying the processes of species adaptive evolution. The goal of our study was to examine spatial distribution of allelic diversity at exon 2 of MHC class II DRB locus across the majority of distribution range of the genus Rupicapra using next generation approach (Ion Torrent S5, Thermo Fisher). We identified 20 alleles in 96 individuals. Twelve alleles had been previously identified in chamois while the remaining 8 are novel. The number of variable nucleotide sites in detected alleles was 23 (10%) and the number of variable amino acid positions in translated sequences was 11 (14%). Out of 20 identified alleles, 18 translated into different amino acid sequences. The number of alleles per individual ranged from 1 to 6 (mean = 3.1), indicating the presence of at least 3 loci resulting from gene duplication events. The most frequent allele, Ruru-DRB*01, was identified in 68 individuals (71%) while 5 alleles were present only in a single individual each. Our results provide evidence of multiple co-amplifying copies, showing that MHC class II DRB is a complex multilocus system with a high level of polymorphism in chamois. Finally, our study represents the first assessment of immunogenetic map of chamois populations that can be used in future conservation management of this species.

major histocompatibility complex, chamois, Rupicapra, next-generation sequencing, gene duplication, allelic polymorphism

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