Divergence of insulin-like growth factors I and II in the elasmobranch, Squalus acanthias

• Published in: FEBS letters 1995-08, Vol.371 (1), p.69-72
• Main Authors: Duguay, Stephen J., Shu Jin Chan, Mommsen, Thomas P., Steiner, Donald F.
• Format: Article
• Language: English
• Subjects: Amino Acid Sequence; Animals; Base Sequence; bp, basepair; Cloning, Molecular; Conserved Sequence - genetics; Dogfish - genetics; Genes - genetics; IGF, insulin-like growth factor; ILP, insulin-like peptide; Insulin-like growth factor; Insulin-Like Growth Factor I - genetics; Insulin-Like Growth Factor II - genetics; Liver - chemistry; Marine; Molecular Sequence Data; Multigene Family; PCR, polymerase chain reaction; Phylogeny; RACE, rapid amplification of cDNA ends; RNA - analysis; RT-PCR, reverse transcriptase PCR; Sequence Alignment; Sequence Homology, Amino Acid; Squalus acanthias; Squalus acanthias (spiny dogfish shark)
• ISSN: 0014-5793; 1873-3468
• DOI: 10.1016/0014-5793(95)00879-E

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.