Characterization of immunoglobulin gamma 1 from a monotreme, Tachyglossus aculeatus

Katherine Belov, Lars Hellman, Desmond W. Cooper

    Research output: Contribution to journalArticlepeer-review

    22 Citations (Scopus)


    A full-length immunoglobulin gamma clone from the echidna (Tachyglossus aculeatus) was isolated from a spleen cDNA library. The clone was 1,664 base pairs long and encoded the entire open reading frame, incorporating the V, D, J and C regions. The echidna clone had approximately 41% identity and 67% similarity at the amino acid level with both marsupial and eutherian IgG molecules. The presence of IgG in the monotremes confirms that the appearance of IgG occurred prior to the separation of the three extant mammalian lineages, but after their separation from the reptilian lineage, pinpointing the date to between 310 and 170 million years ago. Phylogenetic analyses using the immunoglobulin sequence data strongly support the 'Theria' hypothesis, with the monotreme lineage diverging prior to the separation of the marsupial and eutherian lineages.
    Original languageEnglish
    Pages (from-to)1065-1071
    Number of pages7
    Issue number12
    Publication statusPublished - Mar 2002


    • monotreme
    • immunoglobulin
    • evolution
    • IgG
    • IgY


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