title: Cloning and characterization of Xenopus beta2-microglobulin.
abstract: cDNAs for Xenopus beta2-microglobulin (beta2m), the obligatory light chain of most vertebrate Major Histocompatibility Complex (MHC) class I molecules, were isolated and ESTs were identified. Alignment of the deduced amino acid sequence to other species' beta2m showed that the overall structure is evolutionarily conserved, and phylogenetic analysis showed that the Xenopus beta2m sequence is intermediate between fish and bird/mammal beta2m. The Xenopus beta2m mRNA is expressed ubiquitously with highest expression in intestine, spleen, and thymus, correlating well with classical class Ia expression. beta2m mRNA and protein were also detected in Xenopus thymic tumor and kidney cell lines. Segregation analysis on a tetraploid Xenopus laevis family revealed two independently segregating, non-MHC-linked loci. As expected, only one locus was found in the diploid Xenopus tropicalis, strongly suggesting that the two beta2m loci in the tetraploid species were generated by genome-wide duplication, and did not undergo diploidization unlike many other MHC genes.
authors.affiliation: School of Biological & Biomedical Sciences, University of Durham, Durham DH1 3LE, UK.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Stewart
authors.forename: Yuko
authors.initials: Y
authors.lastname: Ohta
authors.forename: Ralph R
authors.initials: RR
authors.lastname: Minter
authors.forename: Terry
authors.initials: T
authors.lastname: Gibbons
authors.forename: Trudy L
authors.initials: TL
authors.lastname: Horton
authors.forename: Pamela
authors.initials: P
authors.lastname: Ritchie
authors.forename: John D
authors.initials: JD
authors.lastname: Horton
authors.forename: Martin F
authors.initials: MF
authors.lastname: Flajnik
authors.forename: Martin D
authors.initials: MD
authors.lastname: Watson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015139:Blotting, Southern; D003001:Cloning, Molecular; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D008297:Male; D008969:Molecular Sequence Data; D010802:Phylogeny; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D014982:Xenopus laevis / Q000235:genetics*; D001613:beta 2-Microglobulin / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism
chemical_list: D001613:beta 2-Microglobulin