Expression of IgM, IgD, and IgY in a Reptile, Anolis carolinensis

The reptiles are the last major group of jawed vertebrates in which the organization of the IGH locus and its encoded Ig H chain isotypes have not been well characterized. In this study, we show that the green anole lizard (Anolis carolinensis) expresses three Ig H chain isotypes (IgM, IgD, and IgY)...

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Published in:The Journal of immunology (1950) 2009-09, Vol.183 (6), p.3858-3864
Main Authors: Wei, Zhiguo, Wu, Qian, Ren, Liming, Hu, Xiaoxiang, Guo, Ying, Warr, Gregory W, Hammarstrom, Lennart, Li, Ning, Zhao, Yaofeng
Format: Article
Language:English
Subjects:
Animals
Evolution, Molecular
Immunoglobulin D
Immunoglobulin Heavy Chains - genetics
Immunoglobulin Isotypes - analysis
Immunoglobulin Isotypes - chemistry
Immunoglobulin Isotypes - genetics
Immunoglobulin M
Immunoglobulins
Immunologic Factors
Phylogeny
Reptiles - genetics
Reptiles - immunology
RNA Splicing
RNA, Messenger - analysis
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Summary:The reptiles are the last major group of jawed vertebrates in which the organization of the IGH locus and its encoded Ig H chain isotypes have not been well characterized. In this study, we show that the green anole lizard (Anolis carolinensis) expresses three Ig H chain isotypes (IgM, IgD, and IgY) but no IgA. The presence of the delta gene in the lizard demonstrates an evolutionary continuity of IgD from fishes to mammals. Although the germline delta gene contains 11 C(H) exons, only the first 4 are used in the expressed IgD membrane-bound form. The mu chain lacks the cysteine in C(H)1 that forms a disulfide bond between H and L chains, suggesting that (as in IgM of some amphibians) the H and L polypeptide chains are not covalently associated. Although conventional IgM transcripts (four C(H) domains) encoding both secreted and membrane-bound forms were detected, alternatively spliced transcripts encoding a short membrane-bound form were also observed and shown to lack the first two C(H) domains (VDJ-C(H)3-C(H)4-transmembrane region). Similar to duck IgY, lizard IgY H chain (upsilon) transcripts encoding both full-length and truncated (IgYDeltaFc) forms (with two C(H) domains) were observed. The absence of an IgA-encoding gene in the lizard IGH locus suggests a complex evolutionary history for IgA in the saurian lineage leading to modern birds, lizards, and their relatives.
ISSN:0022-1767
1550-6606
DOI:10.4049/jimmunol.0803251