title: Unexpected beta2-microglobulin sequence diversity in individual rainbow trout.
abstract: For mammals beta2-microglobulin (beta2m), the light chain of major histocompatibility complex (MHC) class I molecules, is invariant (or highly conserved) and is encoded by a single gene unlinked to the MHC. We find that beta2m of a salmonid fish, the rainbow trout (Oncorhynchus mykiss), does not conform to the mammalian paradigm. Ten of 12 randomly selected beta2m cDNA clones from an individual fish have different nucleotide sequences. A complex restriction fragment length polymorphism pattern is observed with rainbow trout, suggesting multiple beta2m genes in the genome, in excess of the two genes expected from the ancestral salmonid tetraploidy. Additional duplication and diversification of the beta2m genes might have occurred subsequently. Variation in the beta2m cDNA sequences is mainly at sites that do not perturb the structure of the mature beta2m protein, showing that the observed diversity of the trout beta2m genes is not primarily a result of pathogen selection.
authors.affiliation: Department of Structural Biology, Standford University, CA 94305, USA.
authors.forename: B P
authors.initials: BP
authors.lastname: Shum
authors.forename: K
authors.initials: K
authors.lastname: Azumi
authors.forename: S
authors.initials: S
authors.lastname: Zhang
authors.forename: S R
authors.initials: SR
authors.lastname: Kehrer
authors.forename: R L
authors.initials: RL
authors.lastname: Raison
authors.forename: H W
authors.initials: HW
authors.lastname: Detrich
authors.forename: P
authors.initials: P
authors.lastname: Parham
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016384:Consensus Sequence; D017931:DNA Primers; D015342:DNA Probes; D018076:DNA, Complementary; D015723:Gene Library; D014644:Genetic Variation; D006801:Humans; D008099:Liver / Q000276:immunology; D008969:Molecular Sequence Data; D017686:Oncorhynchus mykiss / Q000235:genetics*; D009928:Organ Specificity; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D012333:RNA, Messenger / Q000302:isolation & purification / Q000378:metabolism; D013154:Spleen / Q000276:immunology; D001613:beta 2-Microglobulin / Q000737:chemistry* / Q000235:genetics*
chemical_list: D017931:DNA Primers; D015342:DNA Probes; D018076:DNA, Complementary; D012333:RNA, Messenger; D001613:beta 2-Microglobulin