Cloning and characterization of class 1 and class 2 insulin-like growth factor-I mRNA in Songliao black pig
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Insulin-like growth factor-I (IGF-I) plays a fundamental role in postnatal mammalian growth, development, and metabolism. The mammalian IGF-I gene contains at least six exons from which several different mRNAs are transcribed. In this study, IGF-I mRNA in Songliao black pig liver was investigated using RLM-RACE. Using a 3′-RACE technique, we determined that all mRNA transcripts lacked exon 5 sequence and contained only exon 6 sequence. Using a 5′-RACE technique, we investigated the presence of class 1 and class 2 IGF-I mRNAs. In several other species, the class 1 and class 2 IGF-I polypeptides are generated from mRNAs containing exon 1 or exon 2, respectively. Both class 1 and class 2 IGF-I mRNAs were identified in Songliao black pig liver. Transcription is initiatated upstream of exons 1 and 2 at multiple dispersed start sites to yield two distinct IGF-I mRNA transcript classes which differ in the precursor peptides predicted from their individual leader sequences. Tissue distribution of Songliao black pig class 1 and class 2 IGF-I mRNA was investigated by real-time RT-PCR. Both classes of IGF-I mRNA were expressed in a variety of tissues, however, class 1 IGF-I mRNA was more abundant than class 2 in all tissues.
KeywordsSongliao black pig IGF-I RACE Real-time PCR
This work was funded by National Natural Science Foundation (30771543) and the Promoting Northeast Old Industrial Base Program (2004BA907A22).
- 10.Rotwein P, Pollock KM, Didier DK, Krivi GG (1086) Organization and sequence of the human insulin-like growth factor-I gene. J Biol Chem 261:4828–4832Google Scholar
- 11.Adamo ML, Neuenschwander S, LeRoith D, Roberts CT Jr (1994) Structure, expression, and regulation of the IGF-I gene. Current directions in insulin-like growth factor research. Plemun Press, New York, pp 1–11Google Scholar
- 12.Holthuizen E, LeRoith D, Roberts C, Rotwein P, Spencer EM, Sussenbach JS (1991) Revised nomenclature for the insulin-like growth factor genes and transcripts. In: Spencer EM (ed) Modern concepts of insulin-like growth factors. Elsevier Press, New York, pp 733–736Google Scholar
- 13.Lowe WL Jr, Lasky SR, LeRoith D, Roberts CT Jr (1998) Distribution and regulation of rat insulin-like growth factor-I messenger ribonucleic acids encoding alternative carboxyterminal E-peptides: evidence for differential processing and regulation in the liver. Mol Endocrinol 2:528–534Google Scholar
- 15.Adomo ML, Ben-Hur H, Roberts CT Jr, LeRoith D (1991) Regulation of start site usage in the leader exons of the rat insulin-like growth factor-I gene by development, fasting, and diabetes. Mol Endocrinol 5:1677–1686Google Scholar
- 16.Pell JM, Saunders JC, Gilmour RS (1993) Differential regulation of transcription initiation from insulin-like growth factor-I (IGF-I) leader exons and of tissue IGF-I expression in response to changed growth hormone and nutritional status in sheep. Endocrinology 132:1797–1807PubMedCrossRefGoogle Scholar
- 19.Brameld JM, Atkinson JL, Saunders JC, Pell JM, Buttery PJ, Gilmour RS (1996) Effects of growth hormone administration and dietary protein intake on insulin-like growth factor I and growth hormone receptor mRNA expression in porcine liver, skeletal muscle, and adipose tissue. J Anim Sci 74(8):1832–1841PubMedGoogle Scholar
- 22.Weller PA, Dauncey MJ, Bates PC, Brameld JM, Buttery PJ, Gilmour RS (1994) Regulation of porcine insulin-like growth factor-I and growth hormone receptor mRNA expression by energy status. Am J Physiol 266:776–785Google Scholar