Expression, mitogenic activity and regulation by growth hormone of growth hormone/insulin-like growth factor in Branchiostoma belcheri
- 157 Downloads
The growth hormone (GH)/insulin-like growth factor (IGF) axis is unique to all the vertebrate species but its evolutionary origin is ill-defined. We therefore cloned a cDNA encoding Branchiostoma belcheri IGF (BbIGF). BbIGF was expressed in a tissue-specific manner, with the most abundant expression in the hepatic caecum, the putative liver precursor. The recombinant BbIGF expressed in vitro showed mitogenic activity capable of stimulating cell proliferation in the flounder gill, a characteristic of vertebrate IGF. Quantitative real-time polymerase chain reaction demonstrated that the recombinant rat GH was able to induce a significant up-regulation of BbIGF expression in the hepatic caecum. Moreover, Western blotting revealed the presence of a molecule similar to rat GH receptor in the hepatic caecum. These results suggest that BbIGF expression is inducible by exogenous mammalian GH, suggesting the presence of a GH/IGF axis in B. belcheri. The relationship between BbIFG expression and the origin of the vertebrate liver is discussed.
KeywordsGrowth hormone Insulin-like growth factor Hepatic caecum Amphioxus Lancelet Branchiostoma belcheri
We thank the editor for his help in improving the language of this manuscript.
- Chang C, Chu Y, Chen D (1982) Immunocyctochemical demonstration of luteinizing hormone (LH) in Hatschek’s pit of amphioxus (Branchiostoma belcheri). Kexue Tongbao 27:1233–1234Google Scholar
- Duan C (1997) The insulin-like growth factor system and its biological actions in fish. Am Zool 37:489–501Google Scholar
- Hammar JA (1898) Zur Kenntnis der Leberentwicklung bei Amphioxus. Anat Anz 14:602–606Google Scholar
- Nozaki M, Gorbman A (1992) The question of functional homology of Hatschek’s pit of amphioxus (Branchiostoma belcheri) and the vertebrate adenohypophysis. Zool Sci 9:387–395Google Scholar
- Welsch U (1975) The fine structure of the pharynx, cyrtopodocytes and digestive caecum of amphioxus (Branchiostoma lanceolatum). Symp Zool Soc Lond 36:17–41Google Scholar
- Zheng XY, Jiang ZJ, Shao ML, Li ZJ, Yuan YL (2005) Chinese pharmacopoeia, 2nd edn. Chemical Industry Press, BeijingGoogle Scholar