title: Platypus TCRμ provides insight into the origins and evolution of a uniquely mammalian TCR locus.
abstract: TCRμ is an unconventional TCR that was first discovered in marsupials and appears to be absent from placental mammals and nonmammals. In this study, we show that TCRμ is also present in the duckbill platypus, an egg-laying monotreme, consistent with TCRμ being ancient and present in the last common ancestor of all extant mammals. As in marsupials, platypus TCRμ is expressed in a form containing double V domains. These V domains more closely resemble Ab V than that of conventional TCR. Platypus TCRμ differs from its marsupial homolog by requiring two rounds of somatic DNA recombination to assemble both V exons and has a genomic organization resembling the likely ancestral form of the receptor genes. These results demonstrate that the ancestors of placental mammals would have had TCRμ but it has been lost from this lineage.
authors: Department of Biology, Center for Evolutionary and Theoretical Immunology, University of New Mexico, Albuquerque, NM 87131-1091, USA.
authors: Xinxin
authors: X
authors: Wang
authors: Zuly E
authors: ZE
authors: Parra
authors: Robert D
authors: RD
authors: Miller
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019143:Evolution, Molecular; D056426:Genetic Loci / Q000276:immunology*; D008969:Molecular Sequence Data; D010802:Phylogeny; D010987:Platypus / Q000235:genetics* / Q000276:immunology*; D011948:Receptors, Antigen, T-Cell / Q000235:genetics* / Q000276:immunology* / Q000302:isolation & purification; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D027041:Somatic Hypermutation, Immunoglobulin / Q000235:genetics
chemical_list: D011948:Receptors, Antigen, T-Cell