Trans-species polymorphism of class IIMhc loci in danio fishes |
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Authors: | Robert Graser Colm O'hUigin Vladimir Vincek Axel Meyer Jan Klein |
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Institution: | (1) Max-Planck-Institut für Biologie, Abteilung Immungenetik, Corrensstr. 42, D-72076 Tübingen, Germany, DE;(2) Department of Microbiology and Immunology, University of Miami School of Medicine, Miami, FL 33106, USA, US;(3) Department of Ecology and Evolution, State University of New York at Stony Brook, Stony Brook, NY 11794-6246, USA, US |
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Abstract: | A characteristic feature of the major histocompatibility complex (Mhc) polymorphism in mammals is the existence of allelic lineages shared by related species. This trans-species polymorphism
has thus far been documented only in primates, rodents, and artiodactyls. In this communication we provide evidence that it
also exists in cyprinid (bony) fishes at the class II A and B loci coding for the α and β polypeptide chains of the class II α : β heterodimers. The study has focused on three species
of the family Cyprinidae, subfamily Rasborinae: the zebrafish (Danio rerio), the giant danio (D. malabaricus), and the pearl danio (D. albolineatus). The polymerase chain reaction was used to amplify and then sequence intron 1 and exon 2 of the class II B loci and exon 2 of the class II A loci in these species. Phylogenetic analysis of the sequences revealed the existence of allelic lineages whose divergence
predates the divergence of the three species at both the A and B loci. The lineages at the B locus in particular are separated by large genetic distances. The polymorphism is concentrated in the peptide-binding region
sites and is apparently maintained by balancing selection. Sharing of this unique Mhc feature by both bony fishes and mammals suggests that the main function of the Mhc (presentation of peptides to T lymphocytes) has not changed during the last 400 million years of its evolution.
Received: 6 December 1995 / Revised: 6 February 1996 |
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