Structure, diversity and evolutionary patterns of expressed MHC class IIB genes in chub (Squalius cephalus), a cyprinid fish species from Europe
| Authors | |
|---|---|
| Year of publication | 2011 |
| Type | Article in Periodical |
| Magazine / Source | Immunogenetics |
| MU Faculty or unit | |
| Citation | |
| Doi | http://dx.doi.org/10.1007/s00251-010-0495-3 |
| Field | Immunology |
| Keywords | MHC class IIB genes; Cyprinidae; Selection; Recombination; Polymorphism |
| Description | The polymorphism of exon 2 of the DAB genes (MHC class IIB) was investigated in the freshwater cyprinid fish species, Squalius cephalus in the wide range of its distribution in Europe. We identified 111 different DAB variants in 15 chub populations. The sequence analysis showed that many structurally important amino acid sites that were conserved among tetrapods were also conserved in chub. The analysis of recombination indicated that it does not play an important role in producing and maintaining the variation of DAB genes analyzed in the present study. The exon 2 was shown to be subjected to intense positive selection. Phylogenetic analysis and sequence identities suggest the presence of two class IIB loci in chub. A contrasting selection pattern was found in DAB1-like and DAB3-like genes, which suggests the potential functional differences between these genes.The phylogenetic analyses did not confirm any biogeographical pattern of MHC IIB structure in chub, which is in line with balancing selection and trans-species polymorphism in MHC genes. Nevertheless, cluster analysis based on the presence/ absence of DAB sequence variants in the populations showed the phylogeophraphical pattern corresponding to the mtDNA lineages, which indicates that neutral selection can partially explain the MHC IIB evolution in chub. |
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