Discovery of a unique Ig heavy-chain isotype (IgT) in rainbow trout: Implications for a distinctive B cell developmental pathway in teleost fish

DOI Web Site 被引用文献6件
  • John D. Hansen
    Western Fisheries Research Center, Biological Resources Division and Department of Pathobiology, U.S. Geological Survey and University of Washington, Seattle, WA 98115; Molecular and Cell Biology Program, University of Maryland, Baltimore, MD 21201; and School of Biological Sciences, Washington State University, Vancouver, WA 98686
  • Eric D. Landis
    Western Fisheries Research Center, Biological Resources Division and Department of Pathobiology, U.S. Geological Survey and University of Washington, Seattle, WA 98115; Molecular and Cell Biology Program, University of Maryland, Baltimore, MD 21201; and School of Biological Sciences, Washington State University, Vancouver, WA 98686
  • Ruth B. Phillips
    Western Fisheries Research Center, Biological Resources Division and Department of Pathobiology, U.S. Geological Survey and University of Washington, Seattle, WA 98115; Molecular and Cell Biology Program, University of Maryland, Baltimore, MD 21201; and School of Biological Sciences, Washington State University, Vancouver, WA 98686

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<jats:p>During the analysis of Ig superfamily members within the available rainbow trout (<jats:italic>Oncorhynchus mykiss</jats:italic>) EST gene index, we identified a unique Ig heavy-chain (IgH) isotype. cDNAs encoding this isotype are composed of a typical IgH leader sequence and a VDJ rearranged segment followed by four Ig superfamily C-1 domains represented as either membrane-bound or secretory versions. Because teleost fish were previously thought to encode and express only two IgH isotypes (IgM and IgD) for their humoral immune repertoire, we isolated all three cDNA isotypes from a single homozygous trout (OSU-142) to confirm that all three are indeed independent isotypes. Bioinformatic and phylogenetic analysis indicates that this previously undescribed divergent isotype is restricted to bony fish, thus we have named this isotype “IgT” (τ) for teleost fish. Genomic sequence analysis of an OSU-142 bacterial artificial chromosome (BAC) clone positive for all three IgH isotypes revealed that IgT utilizes the standard rainbow trout V<jats:sub>H</jats:sub>families, but surprisingly, the IgT isotype possesses its own exclusive set of D<jats:sub>H</jats:sub>and J<jats:sub>H</jats:sub>elements for the generation of diversity. The<jats:italic>IgT</jats:italic>D and J segments and τ constant (C) region genes are located upstream of the D and J elements for<jats:italic>IgM</jats:italic>, representing a genomic<jats:italic>IgH</jats:italic>architecture that has not been observed in any other vertebrate class. All three isotypes are primarily expressed in the spleen and pronephros (bone marrow equivalent), and ontogenically, expression of<jats:italic>IgT</jats:italic>is present 4 d before hatching in developing embryos.</jats:p>

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