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Avian Toll-like receptor allelic diversity far exceeds human polymorphism: an insight from domestic chicken breeds

Immune genes show remarkable levels of adaptive variation shaped by pathogen-mediated selection. Compared to humans, however, population polymorphism in animals has been understudied. To provide an insight into immunogenetic diversity in birds, we sequenced complete protein-coding regions of all Tol...

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Bibliographic Details
Published in:Scientific reports 2018-12, Vol.8 (1), p.17878-11, Article 17878
Main Authors: Świderská, Zuzana, Šmídová, Adéla, Buchtová, Lucie, Bryjová, Anna, Fabiánová, Anežka, Munclinger, Pavel, Vinkler, Michal
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Language:English
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Summary:Immune genes show remarkable levels of adaptive variation shaped by pathogen-mediated selection. Compared to humans, however, population polymorphism in animals has been understudied. To provide an insight into immunogenetic diversity in birds, we sequenced complete protein-coding regions of all Toll-like receptor ( TLR ) genes with direct orthology between mammals and birds ( TLR3 , TLR4 , TLR5 and TLR7 ) in 110 domestic chickens from 25 breeds and compared their variability with a corresponding human dataset. Chicken TLRs ( chTLRs ) exhibit on average nine-times higher nucleotide diversity than human TLRs ( hTLRs ). Increased potentially functional non-synonymous variability is found in chTLR ligand-binding ectodomains. While we identified seven sites in chTLRs under positive selection and found evidence for convergence between alleles, no selection or convergence was detected in hTLRs . Up to six-times more alleles were identified in fowl (70 chTLR4 alleles vs. 11 hTLR4 alleles). In chTLRs , high numbers of alleles are shared between the breeds and the allelic frequencies are more equal than in hTLRs . These differences may have an important impact on infectious disease resistance and host-parasite co-evolution. Though adaptation through high genetic variation is typical for acquired immunity (e.g. MHC ), our results show striking levels of intraspecific polymorphism also in poultry innate immune receptors.
ISSN:2045-2322
2045-2322
DOI:10.1038/s41598-018-36226-1