Biomaterial Database

The fate of duplicated major histocompatibility complex class Ia genes in a dodecaploid amphibian, Xenopus ruwenzoriensis. 2002

Bénédicte Sammut, and Anne Marcuz, and Louis Du Pasquier

Basel Institute for Immunology, Switzerland. sammutbe@hotmail.com

The dodecaploid anuran amphibian Xenopus ruwenzoriensis represents the only polyploid species of Xenopus in which the full silencing of the extra copies of the major histocompatibility complex (MHC) has not occurred. Xenopus ruwenzoriensis is a recent polyploid that has evolved within one of the two tetraploid groups of Xenopus through allopolyploidization. Family studies of its MHC haplotype suggested a polysomic inheritance of the MHC class I and II genes. Four class Ia bands can be detected per individual in Southern blot analysis and, similarly, four different cDNA sequences are expressed per individual. The Xenopus class Ia sequences we analyzed belong to only one of the old class I lineages and show a homogenization of their alpha3 domain sequences. This homogenization occurred after speciation within the Xenopus ruwenzoriensis species, either due to gene conversion or inter-alleles/loci recombination.A re-evaluation of the polymorphism of class Ia in Xenopus, by looking at the rate of non-synonymous versus synonymous substitutions, suggests that Xenopus MHC class Ia genes are not under strong overdominant selection. This is a rare situation among vertebrates. The observed polymorphism is most likely due to the interlocus genetic exchanges related to the peculiar mode of speciation of the genus.

UI	MeSH Term	Description	Entries
D008969	Molecular Sequence Data	Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.	Sequence Data, Molecular,Molecular Sequencing Data,Data, Molecular Sequence,Data, Molecular Sequencing,Sequencing Data, Molecular
D011110	Polymorphism, Genetic	The regular and simultaneous occurrence in a single interbreeding population of two or more discontinuous genotypes. The concept includes differences in genotypes ranging in size from a single nucleotide site (POLYMORPHISM, SINGLE NUCLEOTIDE) to large nucleotide sequences visible at a chromosomal level.	Gene Polymorphism,Genetic Polymorphism,Polymorphism (Genetics),Genetic Polymorphisms,Gene Polymorphisms,Polymorphism, Gene,Polymorphisms (Genetics),Polymorphisms, Gene,Polymorphisms, Genetic
D011123	Polyploidy	The chromosomal constitution of a cell containing multiples of the normal number of CHROMOSOMES; includes triploidy (symbol: 3N), tetraploidy (symbol: 4N), etc.	Polyploid,Polyploid Cell,Cell, Polyploid,Cells, Polyploid,Polyploid Cells,Polyploidies,Polyploids
D005805	Genes, MHC Class I	Genetic loci in the vertebrate major histocompatibility complex which encode polymorphic characteristics not related to immune responsiveness or complement activity, e.g., B loci (chicken), DLA (dog), GPLA (guinea pig), H-2 (mouse), RT-1 (rat), HLA-A, -B, and -C class I genes of man.	Class I Genes,Genes, Class I,Genes, H-2 Class I,Genes, HLA Class I,MHC Class I Genes,H-2 Class I Genes,HLA Class I Genes,Class I Gene,Gene, Class I,Genes, H 2 Class I,H 2 Class I Genes
D006824	Hybridization, Genetic	The genetic process of crossbreeding between genetically dissimilar parents to produce a hybrid.	Crossbreeding,Hybridization, Intraspecies,Crossbreedings,Genetic Hybridization,Genetic Hybridizations,Hybridizations, Genetic,Hybridizations, Intraspecies,Intraspecies Hybridization,Intraspecies Hybridizations
D000483	Alleles	Variant forms of the same gene, occupying the same locus on homologous CHROMOSOMES, and governing the variants in production of the same gene product.	Allelomorphs,Allele,Allelomorph
D000595	Amino Acid Sequence	The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.	Protein Structure, Primary,Amino Acid Sequences,Sequence, Amino Acid,Sequences, Amino Acid,Primary Protein Structure,Primary Protein Structures,Protein Structures, Primary,Structure, Primary Protein,Structures, Primary Protein
D000818	Animals	Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA.	Animal,Metazoa,Animalia
D000949	Histocompatibility Antigens Class II	Large, transmembrane, non-covalently linked glycoproteins (alpha and beta). Both chains can be polymorphic although there is more structural variation in the beta chains. The class II antigens in humans are called HLA-D ANTIGENS and are coded by a gene on chromosome 6. In mice, two genes named IA and IE on chromosome 17 code for the H-2 antigens. The antigens are found on B-lymphocytes, macrophages, epidermal cells, and sperm and are thought to mediate the competence of and cellular cooperation in the immune response. The term IA antigens used to refer only to the proteins encoded by the IA genes in the mouse, but is now used as a generic term for any class II histocompatibility antigen.	Antigens, Immune Response,Class II Antigens,Class II Histocompatibility Antigen,Class II Major Histocompatibility Antigen,Ia Antigens,Ia-Like Antigen,Ia-Like Antigens,Immune Response Antigens,Immune-Associated Antigens,Immune-Response-Associated Antigens,MHC Class II Molecule,MHC II Peptide,Class II Antigen,Class II Histocompatibility Antigens,Class II MHC Proteins,Class II Major Histocompatibility Antigens,Class II Major Histocompatibility Molecules,I-A Antigen,I-A-Antigen,IA Antigen,MHC Class II Molecules,MHC II Peptides,MHC-II Molecules,Antigen, Class II,Antigen, I-A,Antigen, IA,Antigen, Ia-Like,Antigens, Class II,Antigens, Ia,Antigens, Ia-Like,Antigens, Immune-Associated,Antigens, Immune-Response-Associated,I A Antigen,II Peptide, MHC,Ia Like Antigen,Ia Like Antigens,Immune Associated Antigens,Immune Response Associated Antigens,MHC II Molecules,Molecules, MHC-II,Peptide, MHC II,Peptides, MHC II
D001483	Base Sequence	The sequence of PURINES and PYRIMIDINES in nucleic acids and polynucleotides. It is also called nucleotide sequence.	DNA Sequence,Nucleotide Sequence,RNA Sequence,DNA Sequences,Base Sequences,Nucleotide Sequences,RNA Sequences,Sequence, Base,Sequence, DNA,Sequence, Nucleotide,Sequence, RNA,Sequences, Base,Sequences, DNA,Sequences, Nucleotide,Sequences, RNA