title: VH gene organization in a relict species, the coelacanth Latimeria chalumnae: evolutionary implications.
abstract: The living coelacanth Latimeria chalumnae is a relict species whose higher-level phylogenetic relationships have not been resolved clearly by traditional systematic approaches. Previous studies show that major differences in immunoglobulin gene structure and organization typify different phylogenetic lineages. To date, mammalian-, avian-, and elasmobranch-type gene organizations have been identified in representatives of these different phylads. A fourth form or organization is found in Latimeria, which possesses immunoglobulin heavy-chain variable region (VH) elements separated by approximately 190 nucleotides from diversity (D) elements. Adjacency of VH and D elements is characteristic of the elasmobranch "clustered" arrangement, although many other features of coelacanth VH gene organization and structure are more similar to those of bony fishes and tetrapods. These observations strongly support a phylogenetic hypothesis in which Latimeria occupies a sister-group relationship with teleosts and tetrapods.
authors.affiliation: University of South Florida, All Children's Hospital, St. Petersburg 33701.
authors.forename: C T
authors.initials: CT
authors.lastname: Amemiya
authors.forename: Y
authors.initials: Y
authors.lastname: Ohta
authors.forename: R T
authors.initials: RT
authors.lastname: Litman
authors.forename: J P
authors.initials: JP
authors.lastname: Rast
authors.forename: R N
authors.initials: RN
authors.lastname: Haire
authors.forename: G W
authors.initials: GW
authors.lastname: Litman
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D016384:Consensus Sequence; D005399:Fishes / Q000235:genetics* / Q000276:immunology; D015723:Gene Library; D005803:Genes, Immunoglobulin / Q000235:genetics*; D016678:Genome; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D015183:Restriction Mapping; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid
chemical_list: D007143:Immunoglobulin Heavy Chains; D007135:Immunoglobulin Variable Region