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Domestication does not narrow MHC diversity in Sus scrofa.
Katerina A Moutou1, Evagelia A Koutsogiannouli, Costas Stamatis
1Laboratory of Cenetics, Evolutionary and Comparative Biology, Department of Biochemistry and Biotechnology, University of Thessaly, Larissa, Greece.
Immunogenetics
|December 15, 2012
Summary
Domestication did not reduce the genetic diversity of the Major Histocompatibility Complex (MHC) in pigs. Wild boars and domestic pigs exhibit similar MHC polymorphism, indicating selection pressures maintain diversity in both populations.
Area of Science:
- Immunogenetics
- Comparative genomics
- Evolutionary biology
Background:
- The Major Histocompatibility Complex (MHC) is a highly polymorphic multigene family crucial for immune response.
- MHC molecules present antigenic peptides via a peptide-binding region (PBR) with distinct pockets.
- Understanding MHC diversity in domestic animals and their wild ancestors is vital for conservation and breeding.
Purpose of the Study:
- To compare the genetic diversity of MHC loci (DQA and DRB1) between domestic pigs and wild boars.
- To investigate the functional polymorphism within the peptide-binding region (PBR) and specific binding pockets.
- To assess the impact of domestication on MHC genetic diversity.
Main Methods:
- Analysis of nucleotide polymorphism in MHC DQA and DRB1 loci from approximately 200 wild boars and 120 domestic pigs.
- Comparison of genetic polymorphism with functional polymorphism in the PBR and binding pockets (P1, P4, P6, P7, P9).
- Statistical analysis to detect positive selection and compare diversity metrics (polymorphism, allelic richness, heterozygosity).
Main Results:
- Wild boars and domestic pigs showed comparable levels of nucleotide and amino acid polymorphism, allelic richness, and heterozygosity in MHC loci.
- Domestication did not act as a genetic bottleneck for MHC diversity.
- Polymorphism was concentrated in the PBR, with evidence of positive selection indicated by an excess of nonsynonymous substitutions.
- P4 and P6 binding pockets were the most polymorphic.
- Functional polymorphism was narrower than genetic polymorphism, suggesting hierarchical selection pressures.
Conclusions:
- Domestication has not significantly diminished MHC genetic diversity in pigs.
- Selection pressures, particularly within the PBR and specific pockets like P4 and P6, maintain MHC diversity in both wild and domestic populations.
- The findings highlight the complex interplay between genetic variation and functional constraints in MHC evolution.
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