Analysis of the Chinese Alligator TCRα/δ Loci Reveals the Evolutionary Pattern of Atypical TCRδ/TCRµ in Tetrapods.
J Immunol
; 205(3): 637-647, 2020 08 01.
Article
em En
| MEDLINE
| ID: mdl-32591403
ABSTRACT
Atypical TCRδ found in sharks, amphibians, birds, and monotremes and TCRµ found in monotremes and marsupials are TCR chains that use Ig or BCR-like variable domains (VHδ/Vµ) rather than conventional TCR V domains. These unconventional TCR are consistent with a scenario in which TCR and BCR, although having diverged from each other more than 400 million years ago, continue to exchange variable gene segments in generating diversity for Ag recognition. However, the process underlying this exchange and leading to the evolution of these atypical TCR receptor genes remains elusive. In this study, we identified two TCRα/δ gene loci in the Chinese alligator (Alligator sinensis). In total, there were 144 V, 154 Jα, nine Jδ, eight Dδ, two Cα, and five Cδ gene segments in the TCRα/δ loci of the Chinese alligator, representing the most complicated TCRα/δ gene system in both genomic structure and gene content in any tetrapod examined so far. A pool of 32 VHδ genes divided into 18 subfamilies was found to be scattered over the two loci. Phylogenetic analyses revealed that these VHδ genes could be related to bird VHδ genes, VHδ/Vµ genes in platypus or opossum, or alligator VH genes. Based on these findings, a model explaining the evolutionary pattern of atypical TCRδ/TCRµ genes in tetrapods is proposed. This study sheds new light on the evolution of TCR and BCR genes, two of the most essential components of adaptive immunity.
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Receptores de Antígenos de Linfócitos T alfa-beta
/
Evolução Molecular
/
Proteínas de Répteis
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Jacarés e Crocodilos
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Loci Gênicos
Tipo de estudo:
Prognostic_studies
Limite:
Animals
Idioma:
En
Ano de publicação:
2020
Tipo de documento:
Article