Complete Coding Sequence of Rainbow Trout Mhc II β Chain

Abstract

Several cDNA clones comprising the entire coding sequence of the rainbow trout (Oncorhynchus mykiss) major histocompatibility comlex (Mhc) class II B gene have been isolated from different sources. A single B gene appears to be transcribed in the rainbow trout and it encodes a 247 amino acid long polypeptide, which is of similar size to mammalian, avian, and amphibian and other teleost beta chains. The amino acid sequence identity to mammalian, amphibian, and avian class II beta chains is only about 30%. Despite the low similarity, a striking pattern of conservation is observed, both in the putative peptide-binding domain and in the Ig-like domain. Most of the conserved residues are located in the Ig-like domain and in the transmembrane segment. The majority of polymorphic residues reside in the beta 1 domain, with the greatest variability found in the amino-terminal half of the domain. The sequence data are compatible with a rather limited polymorphism of a single, expressed Mhc class II B gene.

Modes of Salmonid MHC Class I and II Evolution Differ from the Primate Paradigm

“…These include sequences derived from both genomic DNA (21,22) and cDNA (9,17,19,20,(23)(24)(25). Additional heterogeneity arises from how much of the coding region has been sequenced.…”

“…Hansen et al (9) described three transcribed classical class I alleles in individual fish, while Nakanishi et al (23) reported expression of a classical class I gene from one haploid set of chromosomes in a diploidized genome. For the rainbow trout MHC class II ␤-chain, there is evidence for two loci, although it is not clear whether both are transcribed (18,19,21,24). Recently, the rainbow trout class II ␣-chain, Onmy-DAA, was shown to be encoded by a single, expressed, polymorphic locus (26).…”

Apoptosis of thymocytes in developing sea bassDicentrarchus labrax(L.)

“…The recent molecular cloning of genes encoding major histocompatibility complex (MHC) class I and II in teleosts (Hashimoto et al, 1990;Grimholt et al, 1993;Glamann, 1995;Sultmann et al, 1995) and TCR-and -in the rainbow trout, Oncorhynchus mykiss (Partula et al, 1995(Partula et al, , 1996 indicate conservation of the T cell receptor (TCR) recognition system in bony fish. In MHC class I or II, while the establishment of self-tolerance involves the negative selection of autoreactive T cells through clonal deletion (Pullen et al, 1989) or in the form of anergy (Boyd et al, 1993).…”

Production and characterisation of an antiserum raised against recombinant rainbow trout (Oncorhynchus mykiss) MHC class II beta-chain (MhcOnmy-DAB)

“…However, the presence of Mhc genes has also been demonstrated in non-mammalian vertebrates, such as the chicken (Guillemot & Au#ray, 1989;Miller, 1991), frog (Flajnik & Du Pasquier, 1990;Sato et al, 1993), and a large number of fish species (Dixon et al, 1995), in particular those belonging to the modern bony fishes (teleostei). Representative examples of the latter are the Mhc class II B gene sequences that have been isolated from carp (Hashimoto et al, 1990;Ono et al, 1993a;Van Erp et al, 1996a), zebrafish (Ono et al, 1992), cichlids (Klein et al, 1993;Ono et al, 1993b), Atlantic salmon (Hordvik et al, 1993), striped bass (Walker & McConnell, 1994) and rainbow trout (Juul-Madsen et al, 1992;Glamann, 1995). Comparison of the deduced protein sequences of these genes with those of mammalian Mhc class II chain sequences reveal major similarities.…”