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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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Published in: | Scientific reports 2018-12, Vol.8 (1), p.17878-11, Article 17878 |
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Main Authors: | , , , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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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. |
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ISSN: | 2045-2322 2045-2322 |
DOI: | 10.1038/s41598-018-36226-1 |