engleski

Preliminary research on MHC class II DQB locus variability in brown bear (Ursus arctos) from Croatia

The brown bear (Ursus arctos) is the most widely distributed ursid species, which historically inhabited the majority of Eurasian continent. However, due to extensive hunting and habitat destruction, brown bears in Europe have lost most of their range. Several remnant west-European populations are small and endangered, while large populations reside in Scandinavia, Baltic-Karelian region, Carpathian and Dinaric-Pindos Mountains. The Croatian population, which is estimated at approximately 1000 individuals and legally protected, belongs to the Dinaric-Pindos population. Genetic studies in endangered populations can significantly contribute to establish efficient conservation guidelines. The Major histocompatibility complex (MHC) region includes positively selected immune genes involved in pathogen recognition, mating preferences and susceptibility to infectious and autoimmune diseases. Due to their role in important biological traits, MHC genes represent valuable genetic markers for adaptive genetic variability that determines population capacity for environmental challenges. Using sequencing-cloning and single-strand conformation polymorphism methods in this preliminary research, we analysed 32 brown bear samples from Croatia at MHC class II DQB locus. We identified six unique DQB alleles, three of which were new variants. In six individuals, three alleles were detected and locus duplication was deduced. Alleles Urar-DQB*03 and Urar-DQB*04 were regularly found within the same genotype, and were also present in all three-allelic individuals. That finding indicates that DQB gene duplicates are linked and alleles are inherited as two-locus haplotype, which is presumably favoured by natural selection. We will continue our research with a larger sample set of individuals collected during several years, analysis of additional MHC class II loci and investigating association between MHC polymorphism and resistance / susceptibility to common pathogens that are present in bears.

Brown bear, genetics, MHC

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