Analysis of two IgM isotypes in Atlantic salmon and brown trout

Department of Fisheries and Marine Biology, University of Bergen, Bergen, Norway.
Molecular Immunology (Impact Factor: 2.97). 11/2002; 39(5-6):313-21. DOI: 10.1016/S0161-5890(02)00114-1
Source: PubMed


Atlantic salmon (Salmo salar) possesses two distinct subpopulations of polymeric IgM which are separable by anion exchange chromatography. Consistent with this finding there are two isotypic IgM heavy chain genes, CmuA and CmuB, in the genome of this species, presumably as a result of ancestral tetraploidy. In the present study it was shown that IgM of brown trout (Salmo trutta) is also separated into two subpopulations by anion exchange chromatography, while IgM of rainbow trout (Oncorhynchus mykiss) and Arctic char (Salvelinus alpinus) are eluted in one peak. Molecular cloning of IgM heavy chain cDNAs from brown trout revealed messages of two distinct constant region genes, named CmuA and CmuB. As deduced from the translated cDNA sequences (and in agreement with isoelectric focusing of the corresponding proteins) the mean pI values of the heavy chains in brown trout differ with only 0.14 units, in comparison to a 0.67 unit difference in salmon. Based on the present sequence analysis we suggest that an additional cysteine near the C-terminus of CmuB is critical in relation to the fractionation of IgM by anion exchange chromatography, for example by altering the overall structure of the IgM polymer and the exposure of charged residues. Most likely, the Cmu subvariant with the characteristic extra cysteine residue arose in the ancestor of Atlantic salmon and brown trout, i.e. after the three genera Salmo, Oncorhynchus and Salvelinus radiated.

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    • "As a result of a tetraploid event in the ancestor of the salmonid fish family there are two paralogousIg heavy chain gene complexes (or remnants) in the genome of several species belonging to Salmonidae [17] [18] [19] [20] [21] [22] [23] "

    Advances in Bioscience and Biotechnology 01/2013; 04(04):85-90. DOI:10.4236/abb.2013.44A012
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    • "Antibodies induced in finfish through infection and/or vaccinations are critical to the achievement of long term adaptive immunity of fish rhabdoviruses (Lorenzen and LaPatra, 1999). The presence of immunoglobulin isotypes such as IgD, IgM and IgT (IgZ in zebrafish) have been shown in teleost fish (Hordvik et al., 2002; Danilova et al., 2005; Hansen et al., 2005). Current research indicates that IgMexpressing B cells respond to antigenic stimulation in systemic tissues while IgT-expressing B cells are important to the mucosal immune response (Zhang et al., 2010). "
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    ABSTRACT: This study reports on the immune responses of fish to viral infections. In this review, the innate and acquired host immune responses of fish to viral infections will be considered. These would enable a more comprehensive understanding of fish immunity to viruses. The control of these viral infections are challenging as there are only a few treatments that are effective. Furthermore, the development of vaccines for the control of viruses remains elusive. Viruses are important pathogens affecting both wild and cultured fish. Teleost fish possess an array of defence mechanisms to prevent successful infections of these pathogens which abound in the surrounding aquatic environment. These mechanisms can be grouped as innate (non-specific) and adaptive (specific) immunity. Here the general protective immune mechanisms of fish to viral infections are reviewed. The fundamental components of innate and adaptive immunity present in finfish are similar to their mammalian counterparts in many ways. Once the physical barriers are overcome by the invading pathogen, chemical and genetic barriers kick in. Complement and interferon are part of such chemical barriers. Natural Killer cells also contribute to non-specific immunity through cell-mediated cytotoxicity (CMC). B-lymphocytes and T-lymphocytes are the major players in specific immune response and are the final defence against the pathogens. Developments in genomics have caused remarkable breakthroughs in insight into immune responses in finfish. However, quite a lot of ground remains to be covered. The zebra fish is currently being studied as a model to bridge the gaps in knowledge.
    Nature and Science of Sleep 06/2012; 10(8):70-76.
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    • "However, only approximately 100 kb of the 3' end of one rainbow trout IgH locus has been sequenced to date. Two IgM isotypes were found in Atlantic salmon and brown trout (Salmo trutta), while it has been suggested through gel filtration analysis that rainbow trout and Arctic char (Salvelinus alpinus) possess a single IgM [35]. Moreover, only one Cμ cDNA has been found from a single homozygous rainbow trout, whereas duplicated versions of the rainbow trout Cτ and Cδ genes have been suggested from cDNA variants [22]. "
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    ABSTRACT: The Atlantic salmon (Salmo salar) immunoglobulin heavy chain (IgH) locus possesses two parallel IgH isoloci (IGH-A and IGH-B), that are related to the genomic duplication event in the family Salmonidae. These duplicated IgH loci in Atlantic salmon provide a unique opportunity to examine the mechanisms of genome diversity and genome evolution of the IgH loci in vertebrates. In this study, we defined the structure of these loci in Atlantic salmon, and sequenced 24 bacterial artificial chromosome (BAC) clones that were assembled into the IGH-A (1.1 Mb) and IGH-B (0.9 Mb) loci. In addition, over 7,000 cDNA clones from the IgH variable (VH) region have been sequenced and analyzed. The present study shows that the genomic organization of the duplicated IgH loci in Atlantic salmon differs from that in other teleosts and other vertebrates. The loci possess multiple Cτ genes upstream of the Cμ region, with three of the Cτ genes being functional. Moreover, the duplicated loci possess over 300 VH segments which could be classified into 18 families. This is the largest number of VH families currently defined in any vertebrate. There were significant structural differences between the two loci, indicating that both IGH-A and -B loci have evolved independently in the short time after the recent genome duplication approximately 60 mya. Our results indicate that the duplication of the IgH loci in Atlantic salmon significantly contributes to the increased diversity of the antibody repertoire, as compared with the single IgH locus in other vertebrates.
    BMC Genomics 09/2010; 11(1):486. DOI:10.1186/1471-2164-11-486 · 3.99 Impact Factor
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