Analysis of the Chinese Alligator TCRα/δ Loci Reveals the Evolutionary Pattern of Atypical TCRδ/TCRμ in Tetrapods
- 1 August 2020
- journal article
- research article
- Published by The American Association of Immunologists in The Journal of Immunology
- Vol. 205 (3), 637-647
- https://doi.org/10.4049/jimmunol.2000257
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.Keywords
This publication has 42 references indexed in Scilit:
- A Model for the Evolution of the Mammalian T-cell Receptor / and Loci Based on Evidence from the Duckbill PlatypusMolecular Biology and Evolution, 2012
- A Second TCRδ Locus in Galliformes Uses Antibody-like V Domains: Insight into the Evolution of TCRδ and TCRμ Genes in TetrapodsThe Journal of Immunology, 2012
- Platypus TCRμ Provides Insight into the Origins and Evolution of a Uniquely Mammalian TCR LocusThe Journal of Immunology, 2011
- A Case Of Convergence: Why Did a Simple Alternative to Canonical Antibodies Arise in Sharks and Camels?PLoS Biology, 2011
- The dynamic TCRδ: TCRδ chains in the amphibian Xenopus tropicalis utilize antibody‐like V genesEuropean Journal of Immunology, 2010
- Origin and evolution of the adaptive immune system: genetic events and selective pressuresNature Reviews Genetics, 2009
- The bovine T cell receptor alpha/delta locus contains over 400 V genes and encodes V genes without CDR2Immunogenetics, 2009
- Comparative genomic analysis and evolution of the T cell receptor loci in the opossum Monodelphis domesticaBMC Genomics, 2008
- A unique T cell receptor discovered in marsupialsProceedings of the National Academy of Sciences of the United States of America, 2007
- A dot-matrix program with dynamic threshold control suited for genomic DNA and protein sequence analysisGene, 1995