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Diversification of porcine MHC class II genes: evidence for selective advantage
- Source :
- Immunogenetics. 61(2)
- Publication Year :
- 2008
-
Abstract
- The major histocompatibility complex (MHC) is an immunological gene-dense region of high diversity in mammalian species. Sus scrofa was domesticated by at least six independent events over Eurasia during the Holocene period. It has been hypothesized that the level and distribution of MHC variation in pig populations reflect genetic selection and environmental influences. In an effort to define the complexity of MHC polymorphisms and the role of selection in the generation of class II gene diversity (DQB, DRB1, and pseudogene PsiDRB3), DNA from globally distributed unrelated domestic pigs of European and Asian origins and a Suidae out-group was analyzed. The number of pseudogene alleles identified (PsiDRB3 33) was greater than those found in the expressed genes (DQB 20 and DRB1 23) but the level of observed heterozygosity (PsiDRB3 0.452, DQB 0.732, and DRB1 0.767) and sequence diversity (PsiDRB3 0.029, DQB 0.062, and DRB1 0.074) were significantly lower in the pseudogene, respectively. The substitution ratios reflected an excess of d (N) (DQB 1.476, DRB1 1.724, and PsiDRB3 0.508) and the persistence of expressed gene alleles suggesting the influence of balancing selection, while the pseudogene was undergoing purifying selection. The lack of a clear MHC phylogeographic tree, coupled with close genetic distances observed between the European and Asian populations (DQB 0.047 and DRB1 0.063) suggested that unlike observations using mtDNA, the MHC diversity lacks phylogeographic structure and appears to be globally uniform. Taken together, these results suggest that, despite regional differences in selective breeding and environments, no skewing of MHC diversity has occurred.
- Subjects :
- Asia
Genotype
Swine
Pseudogene
Immunology
Genes, MHC Class II
Molecular Sequence Data
Sus scrofa
Animals, Wild
Balancing selection
Major histocompatibility complex
MHC Class II Gene
Evolution, Molecular
Negative selection
Gene Frequency
Species Specificity
Genetic variation
Genetics
Animals
Amino Acid Sequence
Allele
Selection, Genetic
Alleles
Conserved Sequence
Phylogeny
Genetic diversity
biology
Sequence Homology, Amino Acid
Genetic Variation
Europe
Evolutionary biology
Animals, Domestic
biology.protein
Sequence Alignment
Pseudogenes
Subjects
Details
- ISSN :
- 14321211
- Volume :
- 61
- Issue :
- 2
- Database :
- OpenAIRE
- Journal :
- Immunogenetics
- Accession number :
- edsair.doi.dedup.....8582230cd06c1afb6fdfd00a22244a9c