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Title: BACULOVIRUS-MEDIATED EXPRESSION OF CHICKEN GROWTH HORMONE

Author
item FOSTER, D - UNIVERSITY OF MINNESOTA
item Proudman, John
item HARMON, S - UNIV CALIFORNIA-IRVINE
item FOSTER, L - UNIVERSITY OF MINNESOTA

Submitted to: Molecular Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/21/1997
Publication Date: N/A
Citation: N/A

Interpretive Summary: Growth hormone (GH), produced by the pituitary gland, plays a major role in regulating growth and body composition in mammals. In poultry, the role of GH is less certain. It is known that GH exists in numerous isoforms- molecules which are slightly different in structure. Different isoforms may have different functions in regulating growth and metabolism. Determination of the biological function of GH in poultry requires large quantities of hormone for testing. Because of the many isoforms of GH produced, it is not possible to purify sufficient material from slaughterhouse pituitaries. Recombinant chicken GH has been produced in a bacterial system, but bacteria cannot produce isoforms that are similar to those produced by vertebrates. This study was conducted to produce recombinant chicken GH in a eukaryotic vector, and to assess whether biologically-relevant isoforms would be produced. Results showed that the chicken GH produced by gypsy moth cells was biologically active and displayed an isoform pattern similar to that of natural pituitary GH. However, the quantity of GH produced was disappointing, suggesting that other expression systems should be investigated. This study is the first to demonstrate production of a recombinant avian hormone in a eukaryotic expression system, and shows that such systems can produce biologically- relevant hormone isoforms. Availability of such hormones will enhance research into the role of hormones and their isoforms in regulating growth and reproduction.

Technical Abstract: A full-length chicken growth hormone cDNA was placed downstream from the Autograph californica nuclear polyhedron virus, AcNPV, polyhedron gene promoter and expressed in Sf9 insect cells. Secreted recombinant chicken growth hormone levels averaged 2-10 ug/ml from day 5 to 10 postinfection. The recombinant chicken growth hormone analyzed by SDS-PAGE gels and Western blotting consisted of a doublet with molecular weight of 26.5 and 23.5 kDa. Analysis by 2 D electrophoresis of partially-purified recombinant chicken growth hormone and purified native chicken growth hormone revealed similar immunoreactive charge isoforms and molecular weight variants. The recombinant hormone was biologically active in an homologous radioreceptor assay. The results show that chicken growth hormone expressed in insect cells is biologically and immunologically active, and that a variety of isoforms are secreted which exhibit size and charge properties similar to those of pituitary-derived chicken growth hormone.