title: A nonclassical MHC class I U lineage locus in zebrafish with a null haplotypic variant.
abstract: Three sequence lineages of MHC class I genes have been described in zebrafish (Danio rerio): U, Z, and L. The U lineage genes encoded on zebrafish chromosome 19 are predicted to provide the classical function of antigen presentation. This MHC class I locus displays significant haplotypic variation and is the only MHC class I locus in zebrafish that shares conserved synteny with the core mammalian MHC. Here, we describe two MHC class I U lineage genes, mhc1ula and mhc1uma, that map to chromosome 22. Unlike the U lineage proteins encoded on chromosome 19, Ula and Uma likely play a nonclassical role as they lack conservation of key peptide binding residues, display limited polymorphic variation, and exhibit tissue-specific expression. We also describe a null haplotype at this chromosome 22 locus in which the mhc1ula and mhc1uma genes are absent due to a ~30 kb deletion with no other MHC class I sequences present. Functional and non-functional transcripts of mhc1ula and mhc1uma were identified; however, mhc1uma transcripts were often not amplified or amplified at low levels from individuals possessing an apparently bona fide gene. These distinct U lineage genes may be restricted to the superorder Ostariophysi as similar sequences only could be identified from the blind cavefish (Astyanax mexicanus), fathead minnow (Pimephales promelas), goldfish (Carassius auratus), and grass carp (Ctenopharyngodon idella).
authors.affiliation: Department of Molecular Biomedical Sciences, North Carolina State University, 1060 William Moore Drive, Raleigh, NC, 27607, USA.
authors.forename: Hayley
authors.initials: H
authors.lastname: Dirscherl
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Yoder
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002460:Cell Line; D002874:Chromosome Mapping; D016386:Chromosome Walking; D019143:Evolution, Molecular; D005260:Female; D020869:Gene Expression Profiling; D005838:Genotype; D060005:Genotyping Techniques; D006239:Haplotypes / Q000235:genetics; D015395:Histocompatibility Antigens Class I / Q000145:classification* / Q000235:genetics*; D008297:Male; D008969:Molecular Sequence Data; D011110:Polymorphism, Genetic / Q000235:genetics; D015027:Zebrafish / Q000235:genetics* / Q000276:immunology
chemical_list: D015395:Histocompatibility Antigens Class I