ZFIN ID: ZDB-PUB-070303-31
A third broad lineage of major histocompatibility complex (MHC) class I in teleost fish; MHC class II linkage and processed genes
Dijkstra, J.M., Katagiri, T., Hosomichi, K., Yanagiya, K., Inoko, H., Ototake, M., Aoki, T., Hashimoto, K., and Shiina, T.
Date: 2007
Source: Immunogenetics   59(4): 305-321 (Journal)
Registered Authors: Aoki, Takashi
Keywords: MHC class I, Evolution, Linkage, Processed genes, Rainbow trout
MeSH Terms:
  • Amino Acid Sequence
  • Animals
  • Exons
  • Gene Expression
  • Genes, MHC Class I*
  • Genes, MHC Class II*
  • Genetic Linkage
  • Histocompatibility Antigens Class I/chemistry
  • Histocompatibility Antigens Class I/classification*
  • Histocompatibility Antigens Class I/genetics
  • Histocompatibility Antigens Class II/chemistry
  • Histocompatibility Antigens Class II/classification*
  • Histocompatibility Antigens Class II/genetics
  • Introns
  • Molecular Sequence Data
  • Oncorhynchus mykiss/genetics*
  • Oncorhynchus mykiss/immunology*
  • Pseudogenes
PubMed: 17318646 Full text @ Immunogenetics
Most of the previously studied teleost MHC class I molecules can be classified into two broad lineages: "U" and "Z/ZE." However, database reports on genes in cyprinid and salmonid fishes show that there is a third major lineage, which lacks detailed analysis so far. We designated this lineage "L" because of an intriguing linkage characteristic. Namely, one zebrafish L locus is closely linked with MHC class II loci, despite the extensively documented nonlinkage of teleost class I with class II. The L lineage consists of highly variable, nonclassical MHC class I genes, and has no apparent orthologues outside teleost fishes. Characteristics that distinguish the L lineage from most other MHC class I are (1) absence of two otherwise highly conserved tryptophan residues W51 and W60 in the alpha1 domain, (2) a low GC content of the alpha1 and alpha2 exons, and (3) an HINLTL motif including a possible glycosylation site in the alpha3 domain. In rainbow trout (Oncorhynchus mykiss) we analyzed several intact L genes in detail, including their genomic organization and transcription pattern. The gene Onmy-LAA is quite different from the genes Onmy-LBA, Onmy-LCA, Onmy-LDA, and Onmy-LEA, while the latter four are similar and categorized as "Onmy-LBA-like." Whereas the Onmy-LAA gene is organized like a canonical MHC class I gene, the Onmy-LBA-like genes are processed and lack all introns except intron 1. Onmy-LAA is predominantly expressed in the intestine, while the Onmy-LBA-like transcripts display a rather homogeneous tissue distribution. To our knowledge, this is the first description of an MHC class I lineage with multiple copies of processed genes, which are intact and transcribed. The present study significantly improves the knowledge of MHC class I variation in teleosts.