title: Cloning and sequence analysis of two isotypic IgM heavy chain genes from Atlantic salmon, Salmo salar L.
abstract: A leukocyte cDNA library from Atlantic salmon, based on oligo-dT priming, was constructed in lambda-gt10. Immunoglobulin heavy chain (IgH) cDNA were isolated from the library using a specific probe generated by polymerase chain reaction (PCR) between two conserved areas within the variable region (second and fourth frame region). Two cDNA clones encoding the entire constant region of membrane-bound IgH, and one cDNA encoding the entire constant region of secretory IgH were sequenced, revealing messages from two isotypic IgM genes. Both genes were shown to be present in haploid embryos and have been isolated from a genomic library, the exons and deduced amino acid sequences of which are presented here (salmon CHA and CHB). The splicing of transcripts encoding the membrane-bound IgH excises the whole fourth exon as in other teleosts. The nucleotide and amino acid identity between salmon CHA and CHB are 98.2%, and 96.2%, respectively. Two subfractions of IgM from Atlantic salmon separated by ion chromatography can be explained by a net exchange of basic residues in salmon CHB compared to CHA. The finding of two closely related salmon CH genes is in accordance with the quasi-tetraploid state of the Atlantic salmon genome.
authors.affiliation: Center of Biotechnology, University of Bergen, Norway.
authors.forename: I
authors.initials: I
authors.lastname: Hordvik
authors.forename: A M
authors.initials: AM
authors.lastname: Voie
authors.forename: J
authors.initials: J
authors.lastname: Glette
authors.forename: R
authors.initials: R
authors.lastname: Male
authors.forename: C
authors.initials: C
authors.lastname: Endresen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D005803:Genes, Immunoglobulin; D007127:Immunoglobulin Constant Regions / Q000235:genetics; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007132:Immunoglobulin Isotypes / Q000235:genetics*; D007075:Immunoglobulin M / Q000235:genetics*; D008969:Molecular Sequence Data; D012474:Salmon / Q000235:genetics* / Q000276:immunology
chemical_list: D007127:Immunoglobulin Constant Regions; D007143:Immunoglobulin Heavy Chains; D007132:Immunoglobulin Isotypes; D007075:Immunoglobulin M