Evidence that the separation of Mhc class II from class I loci in the zebrafish, Danio rerio, occurred by translocation.
In the zebrafish, Danio rerio, and other teleosts, the class I and class II loci of the major histocompatibility complex ( Mhc) reside on different chromosomes. To shed light on the events that might have generated this difference from tetrapods, in which these two types of loci are clustered in a single chromosomal region, the organization of the class II loci in linkage group 8 of the zebrafish was determined by the characterization of contigs of PAC clones. Three contigs were defined: DAB, DCB, and DBB. The 350-kb-long DAB contig contained only four genes: DDB, DAB, SLC7A4, and DAA. The 150-kb-long DCB contig contained the DCB, DCA, and fz10 genes at an undetermined distance from the DAB contig. And the 120-kb-long DBB contig comprised the DBB gene presumably in another linkage group. The low gene density of the linkage group 8 contigs, contrasting with the high gene density of the zebrafish class I region, and the close association with genes [ SLC7A4 coding for an amino acid transporter, and fz10 (frizzled 10) coding for a receptor of the WNT glycoprotein] that are not linked with the tetrapod Mhc, is interpreted to mean that the separation of the class II from class I loci in teleosts occurred by translocation rather than by genomic or chromosomal duplication.
Kuroda
Noriyuki
N
Max-Planck-Institut für Biologie, Abteilung Immungenetik, Corrensstrasse 42, 72076 Tübingen, Germany.
Figueroa
Felipe
F
O'hUigin
Colm
C
Klein
Jan
J
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002874:Chromosome Mapping; D027042:Chromosomes, Artificial, P1 Bacteriophage / Q000235:genetics; D004247:DNA / Q000235:genetics; D019143:Evolution, Molecular; D005805:Genes, MHC Class I; D005802:Genes, MHC Class II; D008957:Models, Genetic; D008969:Molecular Sequence Data; D005810:Multigene Family; D016366:Open Reading Frames; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D014178:Translocation, Genetic; D015027:Zebrafish / Q000235:genetics* / Q000276:immunology*
D004247:DNA