|Chen Hung-chih, Mark|
Submitted to: General and Comparative Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/19/2006
Publication Date: 10/2/2006
Citation: Chen Hung-Chih, M., Li, Y., Chang, Y., Wu, S., Gong, H., Lin, G., Chen, T.T., Wu, J. 2006. Co-induction of hepatic IGF-I and progranulin mRNA by growth hormone in tilapia, Oreochromis mossambiccus. General and Comparative Endocrinology. 150:212-218. Interpretive Summary: Somatic growth is an important factor for aquaculture production afficiency. Although it has been shown that growth hormone and insulin-like growth factor-I are involved in regulating somatic growth of fishes, it is not entirely sure whether hormonal factors are working in concert with growth hormone and insulin-like growth factor-I to regulate fish growth.Our goal was to identify whether there are other hormonal factors that could work in concert with growth hormone to regulate somatic growth of fish. We have identified the cDNA of “progranulin” and determined that the expression of this gene is regulated by growth hormone. Since the production of progranulin and insulin-like growth factor-I in the liver of fish is regulated by growth hormone, it suggests that both hormonal factors are involved in growth hormone mediated somatic growth. Further studies on progranulin will help to shed light on how growth hormone regulates somatic growth in fish.
Technical Abstract: Like IGF-I, progranulin (pgrn) is a growth factor involved in tumorigenesis and wound healing. We report here the identification and characterization of pgrn cDNA in tilapia and the regulation of its expression by growth hormone(GH). The tilapia pgrn cDNA was cloned by RT-PCR ampliWcation, using gene specific oligonucleotides as amplification primers. The cDNA contains an open reading frame encoding a peptide of 206 amino acid residues (aa) that contains a presumptive signal peptide (23 aa) and two repeat units of granulin (grn, 51 and 52 aa, respectively) franked by a GAP of 49 aa and the carboxyl terminus with 31 aa. The two predicted grn peptides are arranged in tandem repeats interrupted by a GAP peptide. RT-PCR analysis revealed that high levels of prgn mRNA were present in several tissues such as spleen, gastric cecum, intestine, fat tissue, gill, kidney, eye and pancreas, and lower levels in liver, muscle, heart, brain, skin and stomach. Administration of a single dose (500 ng/g body weight) of recombinant seabream growth hormone (rbGH) by intraperitoneal(ip) injection into one-month-old tilapia resulted in an obvious increase of IGF-I and pgrn mRNA (2.7-fold and 2.5-fold, respectively) in the liver at three hours post-GH treatment. The peptide levels of pgrn in the liver of GH-treated fish also were substantially induced over controls at 12 h post-GH treatment as detected by western immuno-blot analysis. The co-induction of IGF-I and pgrn following GH treatment may suggest the involvement of pgrn in GH regulated growth in tilapia.