Expression of endogenous and exogenous growth hormone (GH) messenger (m) RNA in a GH-transgenic tilapia (Oreochromis niloticus)

• Published in: Transgenic research Vol. 14; no. 1; pp. 95 - 104
• Main Authors: Caelers, A, Maclean, N, Hwang, G, Eppler, E, Reinecke, M
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer 01.02.2005; Springer Nature B.V
• Subjects: animal organs; animal tissues; Animals; Animals, Genetically Modified - genetics; antifreeze promoter; Base Sequence; Biological and medical sciences; Biotechnology; DNA Primers; Fish; Fundamental and applied biological sciences. Psychology; Gene expression; gene transfer; Genetic engineering; Genetic technics; genetic transformation; Growth Hormone - genetics; Liver - metabolism; Macrozoarces americanus; Male; marine fish; messenger RNA; Methods. Procedures. Technologies; Oncorhynchus tshawytscha; Oreochromis niloticus; polymerase chain reaction; promoter regions; recombinant DNA; RNA, Messenger - genetics; somatotropin; Tilapia - genetics; Transgenes; transgenic animals; Transgenic animals and transgenic plants; Vertebrata; Oreochromis niloticus; Messenger RNA; absolute quantification; Pisces; Somatotropin hormone; Tilapia; mRNA; growth hormone; transgene tilapia; Transgenesis; ocean pout antifreeze promoter
• ISSN: 0962-8819; 1573-9368
• DOI: 10.1007/s11248-004-5791-y

We have previously produced transgenic fish from crosses between a wild-type female tilapia (Oreochromis niloticus) and a G transgenic male. This line of growth-enhanced tilapia carries a single copy of a chinook salmon (s) growth hormone (GH) gene spliced to an ocean pout antifreeze promoter (OPA-FPcsGH) co-ligated to a carp beta-actin/lacZ reporter gene construct, integrated into the tilapia genome. Because little is known about the expression sites of transgenes, we have characterised the gene expression patterns of sGH and tilapia (t)GH in transgenic tilapia using a newly established real-time PCR to measure the absolute mRNA amounts of both hormones. The sGH gene, which was expected to be expressed mainly in liver, was also found to be expressed in other organs, such as gills, heart, brain, skeletal muscle, kidney, spleen, intestine and testes. However, in pituitary no sGH mRNA but only tGH mRNA was found. Tilapia GH mRNA in wild-type pituitary amounted to 226 +/- 30 pg/microg total RNA but in transgenics only to 187 +/- 43 pg/microg total RNA. Liver exhibited the highest level of sGH mRNA (8.3 +/- 2.5 pg/microg total RNA) but the extrahepatic sites expressed considerable amounts of sGH mRNA ranging from 4.1 +/- 2.0 pg/microg total RNA in gills to 0.2 +/- 0.08 pg/microg total RNA in kidney. The widespread expression of the sGH gene is assumed to be due to the tissue specificity of the type III AFP gene promoter. It is assumed that our transgenic experiments, which in contrast to some other approaches caused no obvious organ abnormalities, mimick the GH expression during ontogeny. Because sGH mRNA is expressed both in liver and in extrahepatic sites it may not only promote secretion and release of liver-derived (endocrine) IGF-I leading to an overall growth enhancement but also stimulate IGF-I expression within the different organs in a paracrine/autocrine manner and, thus, further promote organ growth.