Department of Biology, Center for Evolutionary and Theoretical Immunology, University of New Mexico, Albuquerque, NM 87131-1091, USA.
J Immunol. 2011 Nov 15;187(10):5246-54. doi: 10.4049/jimmunol.1101113. Epub 2011 Oct 5.
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.
TCRμ 是一种非常规的 TCR，最初在有袋动物中发现，似乎不存在于胎盘哺乳动物和非哺乳动物中。在这项研究中，我们表明 TCRμ 也存在于鸭嘴兽中，鸭嘴兽是一种产卵的单孔目动物，这表明 TCRμ 是古老的，存在于所有现存哺乳动物的最后共同祖先中。与有袋动物一样，鸭嘴兽的 TCRμ 以包含双 V 结构域的形式表达。这些 V 结构域比常规 TCR 的更类似于 Ab V。鸭嘴兽的 TCRμ 与其有袋动物同源物不同，需要两轮体细胞 DNA 重组来组装两个 V 外显子，并且具有类似于受体基因的可能祖先形式的基因组组织。这些结果表明，胎盘哺乳动物的祖先本应具有 TCRμ，但它已从该谱系中丢失。
