title: Divergence of insulin-like growth factors I and II in the elasmobranch, Squalus acanthias.
abstract: Recent studies have shown that vertebrates, including teleostean fishes, amphibians, birds and mammals, contain two distinct insulin-like growth factor (IGF) genes. In contrast agnathans, represented by hagfish, apparently have only one IGF that has features characteristic of both IGF-I and IGF-II. Between these groups the elasmobranchs occupy a critical position in terms of the phylogeny of IGFs. We sought to determine if gene duplication and divergence of IGF-I and IGF-II occurred before or after divergence of elasmobranchs from other vertebrates by cloning IGF-like molecules from Squalus acanthias. Our analysis shows that Squalus liver produces two distinct IGF-like molecules. One has greater sequence identity to, and conserved features characteristic of, known IGF-I molecules, while the other is more IGF-II like. These results suggest that the prototypical IGF molecule duplicated and diverged in an ancestor of the extant gnathostomes.
authors.affiliation: Howard Hughes Medical Institute, University of Chicago, IL 60637, USA.
authors.forename: S J
authors.initials: SJ
authors.lastname: Duguay
authors.forename: S J
authors.initials: SJ
authors.lastname: Chan
authors.forename: T P
authors.initials: TP
authors.lastname: Mommsen
authors.forename: D F
authors.initials: DF
authors.lastname: Steiner
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D017124:Conserved Sequence / Q000235:genetics; D004284:Dogfish / Q000235:genetics*; D005796:Genes / Q000235:genetics*; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D007335:Insulin-Like Growth Factor II / Q000235:genetics*; D008099:Liver / Q000737:chemistry; D008969:Molecular Sequence Data; D005810:Multigene Family; D010802:Phylogeny; D012313:RNA / Q000032:analysis; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid
chemical_list: D012313:RNA; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II