Cloning, molecular characterization and expression analysis of insulin-like growth factor binding protein-2 (IGFBP-2) cDNA in goldfish, Carassius auratus

Abstract

In the present study, a full-length cDNA encoding the insulin-like growth factor binding protein-2 (IGFBP-2) was cloned from the liver of goldfish (Carassius auratus) by rapid amplification of cDNA ends technique. The goldfish IGFBP-2 cDNA sequence was 1,513 bp long and had an open reading frame of 825 bp encoding a predicted polypeptide of 274 amino acid residues. Semi-quantitative RT-PCR results revealed that goldfish IGFBP-2 mRNA was expressed in all detected tissues. In liver, central nervous system and pituitary gland, goldfish IGFBP-2 expressed at high levels, followed by anterior intestine, middle intestine and kidney. In posterior intestine, ovary, skin, fat, spleen, muscle and gill, the goldfish IGFBP-2 expression levels were very low. Fasting and refeeding experiment showed that the mRNA expression of goldfish IGFBP-2 was up-regulated significantly in liver compared to the fed group and restored rapidly to normal level after refed. However, the mRNA expressions of IGFBP-2 in hypothalamus and pituitary of goldfish were insensitive to fasting. Furthermore, the mRNA expressions of IGFBP-2 in hypothalamus, pituitary and liver were varied in periprandial changes and significantly down-regulated at 2 and 4 h after meal. These results imply that the IGFBP-2 mRNA expression may be associated with anabolic and catabolic metabolism and regulated by metabolic factors in goldfish.

Daily Rhythms in the IGF-1 System in the Liver of Goldfish and Their Synchronization to Light/Dark Cycle and Feeding Time

“…Our results show that both IGFBP1 and IGFBP2 encoding genes are expressed in the liver of goldfish and support the synthesis of these proteins in this tissue [ 31 , 32 ]. It is generally accepted that the liver is the predominant source of circulating IGFBPs in different teleosts [ 26 ], e.g., the liver exhibits a higher abundance of IGFBP transcripts than any other tissue in the Atlantic salmon, 95% of which comprised IGFBP1 and IGFBP2 paralogs [ 58 ].…”

“…Members of the IGFBP family share sequence homology, but its regulation and the possibly distinct functional roles of this IGFBPs variety remain unsolved. Nevertheless, IGFBP1 and IGFBP2 have been reported as the main subtypes expressed in the liver of goldfish [ 31 , 32 ].…”