engleski

Variability and duplication of MHC class II DRB1 locus in the Croatian wild boar (Sus scrofa)

Major histocompatibility complex (MHC) class II genes code for protein receptors expressed on the surface of professional antigen-presenting cells. These receptors bind foreign antigens derived from extracellular pathogens and present them to T cells, which initiate an adaptive immune response. MHC genetic region contains some of the most polymorphic coding genes in the vertebrate genome and MHC genes represent some of the best candidates for studying the processes of adaptive evolution. The wild boar is an important game species and an ancestor of the domestic pig. It is considered one of the most widespread species. However, while many data are available on MHC variability in domestic pigs, only few studies have been performed in wild boars. The MHC region in swine, called the swine leukocyte antigen (SLA), is characterised based on research on domestic pig, and includes one functional gene (DRB1) and four pseudogenes. However, duplication of DRB1 gene was recently suggested. The goal of this study was to investigate variability and evolution of the fulllength MHC class II SLA-DRB1 locus exon 2. We analysed 133 wild boar samples from Croatia using direct sequencing and cloning methods. A considerable amount of nucleotide polymorphism of SLADRB1 in the Croatian wild boar population was detected, since 20 notably divergent alleles were found, eight of which were new. A recent discovery of duplication of the DRB1 gene in swine was confirmed by our results, as we identified eight individuals with three alleles. Furthermore, our phylogenetic reconstruction suggested the duplication event was recent, as paralogous sequences had not accumulated sufficient divergence to be apparent as distinct clusters. Since locus duplication has not been found in other investigations on the SLA region, the molecular organization of the MHC class II region in swine should be further investigated and probably reconsidered.

wild boar, MHC genes, variability, duplication

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