Molecular cloning and tissue expression of the insulin-like growth factor II prohormone in the bony fish Cottus scorpius.
The cDNA encoding pro-IGF-II of an advanced teleost fish, Cottus scorpius (Scorpaeniformes), the daddy sculpin, was isolated from liver by RT-PCR and molecular cloning. Like other IGFs, the deduced 168 amino acid peptide contains B-, C-, A-, D-, and E-domains and six cysteine residues (CysB9, CysB21, CysA6, CysA7, CysA11, and CysA20) necessary for the maintenance of tertiary structure. At the amino acid level, the sculpin IGF-II prohormone exhibits 85-92% homology to pro-IGF-II of other bony fish but only 51% homology to human. The mature sculpin IGF-II peptide comprises 70 amino acids. Its A-, B-, and D-domains exhibit homologies as high as 91, 91, and 100%, respectively, when compared with the other bony fish species studied. The high sequence homologies may indicate a particular physiological impact of IGF-II in bony fish. RT-PCR followed by Southern blotting revealed an IGF-II mRNA transcript of the expected size in liver, pyloric and splenic islets, stomach, small and large intestine, kidney, gill, testis, ovary, brain, and heart. The local production of IGF-II in many organs indicates that IGF-II is involved in organ-specific functions in a paracrine/autocrine manner. Furthermore, the results show that all bony fish organs which have been demonstrated to express IGF-I mRNA also express IGF-II mRNA.
Loffing-Cueni
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Division of Neuroendocrinology, Institute of Anatomy, University of Zürich, Zürich, CH-8057, Switzerland.
Schmid
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AC
Reinecke
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M
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D015139:Blotting, Southern; D003001:Cloning, Molecular; D005399:Fishes / Q000378:metabolism*; D006801:Humans; D007335:Insulin-Like Growth Factor II / Q000096:biosynthesis*; D008099:Liver / Q000378:metabolism; D008969:Molecular Sequence Data; D020133:Reverse Transcriptase Polymerase Chain Reaction
D007335:Insulin-Like Growth Factor II