Dataset Information

A model for the evolution of the mammalian t-cell receptor ?/? and ? loci based on evidence from the duckbill Platypus.

ABSTRACT: The specific recognition of antigen by T cells is critical to the generation of adaptive immune responses in vertebrates. T cells recognize antigen using a somatically diversified T-cell receptor (TCR). All jawed vertebrates use four TCR chains called ?, ?, ?, and ?, which are expressed as either a ?? or ?? heterodimer. Nonplacental mammals (monotremes and marsupials) are unusual in that their genomes encode a fifth TCR chain, called TCRµ, whose function is not known but is also somatically diversified like the conventional chains. The origins of TCRµ are also unclear, although it appears distantly related to TCR?. Recent analysis of avian and amphibian genomes has provided insight into a model for understanding the evolution of the TCR? genes in tetrapods that was not evident from humans, mice, or other commonly studied placental (eutherian) mammals. An analysis of the genes encoding the TCR? chains in the duckbill platypus revealed the presence of a highly divergent variable (V) gene, indistinguishable from immunoglobulin heavy (IgH) chain V genes (VH) and related to V genes used in TCRµ. They are expressed as part of TCR? repertoire (VH?) and similar to what has been found in frogs and birds. This, however, is the first time a VH? has been found in a mammal and provides a critical link in reconstructing the evolutionary history of TCRµ. The current structure of TCR? and TCRµ genes in tetrapods suggests ancient and possibly recurring translocations of gene segments between the IgH and TCR? genes, as well as translocations of TCR? genes out of the TCR?/? locus early in mammals, creating the TCRµ locus.

SUBMITTER: Parra ZE

PROVIDER: S-EPMC3457774 | biostudies-literature | 2012 Oct

REPOSITORIES: biostudies-literature

ACCESS DATA

Publications

A model for the evolution of the mammalian t-cell receptor α/δ and μ loci based on evidence from the duckbill Platypus.

Parra Zuly E ZE Lillie Mette M Miller Robert D RD

Molecular biology and evolution 20120515 10

The specific recognition of antigen by T cells is critical to the generation of adaptive immune responses in vertebrates. T cells recognize antigen using a somatically diversified T-cell receptor (TCR). All jawed vertebrates use four TCR chains called α, β, γ, and δ, which are expressed as either a αβ or γδ heterodimer. Nonplacental mammals (monotremes and marsupials) are unusual in that their genomes encode a fifth TCR chain, called TCRµ, whose function is not known but is also somatically dive ...[more]

PMID: 22593227

Similar Datasets

Project description:BACKGROUND:Vertebrate alpha (alpha)- and beta (beta)-globin gene families exemplify the way in which genomes evolve to produce functional complexity. From tandem duplication of a single globin locus, the alpha- and beta-globin clusters expanded, and then were separated onto different chromosomes. The previous finding of a fossil beta-globin gene (omega) in the marsupial alpha-cluster, however, suggested that duplication of the alpha-beta cluster onto two chromosomes, followed by lineage-specific gene loss and duplication, produced paralogous alpha- and beta-globin clusters in birds and mammals. Here we analyse genomic data from an egg-laying monotreme mammal, the platypus (Ornithorhynchus anatinus), to explore haemoglobin evolution at the stem of the mammalian radiation. RESULTS:The platypus alpha-globin cluster (chromosome 21) contains embryonic and adult alpha- globin genes, a beta-like omega-globin gene, and the GBY globin gene with homology to cytoglobin, arranged as 5'-zeta-zeta'-alphaD-alpha3-alpha2-alpha1-omega-GBY-3'. The platypus beta-globin cluster (chromosome 2) contains single embryonic and adult globin genes arranged as 5'-epsilon-beta-3'. Surprisingly, all of these globin genes were expressed in some adult tissues. Comparison of flanking sequences revealed that all jawed vertebrate alpha-globin clusters are flanked by MPG-C16orf35 and LUC7L, whereas all bird and mammal beta-globin clusters are embedded in olfactory genes. Thus, the mammalian alpha- and beta-globin clusters are orthologous to the bird alpha- and beta-globin clusters respectively. CONCLUSION:We propose that alpha- and beta-globin clusters evolved from an ancient MPG-C16orf35-alpha-beta-GBY-LUC7L arrangement 410 million years ago. A copy of the original beta (represented by omega in marsupials and monotremes) was inserted into an array of olfactory genes before the amniote radiation (>315 million years ago), then duplicated and diverged to form orthologous clusters of beta-globin genes with different expression profiles in different lineages.

Dataset Information

A model for the evolution of the mammalian t-cell receptor ?/? and ? loci based on evidence from the duckbill Platypus.

Publications

A model for the evolution of the mammalian t-cell receptor α/δ and μ loci based on evidence from the duckbill Platypus.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets