Evolution of duplicated IgH loci in Atlantic salmon, Salmo salar
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 (1.1Mb) 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.
Results: 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 Ctau genes upstream of the Cmu region, with three of the Ctau 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.
Conclusions: 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.
Author: Motoshige YasuikeJohan de BoerKristian von SchalburgGlenn CooperLinda McKinnelAmber MessmerStacy SoWilliam DavidsonBen Koop
Credits/Source: BMC Genomics 2010, 11:486
Published on: 2010-09-02
Copyright by the authors listed above - made available via BioMedCentral (Open Access). Please
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