Expression of recombinant tilapia insulin-like growth factor-I and stimulation of juvenile tilapia growth by injection of recombinant IGFs polypeptides

Ž . Mature recombinant tilapia insulin-like growth factor-I IGF-I polypeptide was produced in Ž Escherichia coli by cloning the IGF-I B to D domains with glutathione-S-transferase GST, . pGEX-2T vector . The recombinant IGF-I fusion protein, produced following induction of E. coli with IPTG induction and digestion with thrombin, appeared as a major protein band with a Žw x . molecular mass of 7 kDa. Recombinant tilapia IGF-I GSPGIHM -IGF-I polypeptide bioactivity, w x as measured in a homologous H thymidine incorporation assay assessing concentrations ranging w x from 0 to 120 nM, was found to significantly stimulate cell uptake of H thymidine. The stimulatory effect of recombinant tilapia IGF-I polypeptide is suggested to be dose dependent. Ž Recombinant tilapia IGF-I and IGF-II polypeptides at doses of 0.1, 0.5, 1 and 2 mg g body .y1 Ž weight per fish were injected into juvenile tilapia once a week. At doses of 2 mg IGF-I g .y1 Ž .y1 body weight per fish and doses of 2 mg IGF-II g body weight per fish , there were Ž . Ž significant increases P-0.01 from week 5 onwards in both body weight 73% for IGF-I, . Ž . Ž 72% for IGF-II , weight gain 270% for IGF-I, 260% for IGF-II , and body length 33% for IGF-I, ) Corresponding author. Tel.: q886-2-27899534; fax: q886-2-27824595 0044-8486r00r$ see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž . PII: S0044-8486 99 00239-2 ( ) J.-Y. Chen et al.rAquaculture 181 2000 347–360 348 . 34% for IGF-II relative to a similarly treated GST protein control group and untreated group. q 2000 Elsevier Science B.V. All rights reserved.