Development and Application of Fish Growth Hormone Gene (Abstract)

Abstract

Growth hormone is a member of a family composed of prolactin, somatolactin, and placental lactogen. It is synthesized, produced, and stored by pituitary somatotroph cells. The secreted growth hormone stimulates the production of insulin-like growth factors which mediate many of its growth-promoting effects. In this study we cloned growth hormone genes from ayu (Plecoglossus altivelis), grouper (Epinephelus awoara) and zebrafish (Danio rerio). With high homology and similarity, the putative growth hormone polypeptides contain 209, 205 and 211 amino acids respectively. Two functional recombinant GHs were expressed from E coli expression system. By inserting the zebrafish GH gene promoter region to pEGFP-1 vector, we analyzed the promoter activity by introducing the constructs into a rat pituitary cell line and zebrafish embryos. Through the fluorescent microscope, green fluorescent protein expression in the developmental stages of transgenic embryos was observed. To identify the timing and spacing of growth hormone expression during embryogenesis, whole mount in situ hybridization was also performed. As a result, growth hormone mRNA was detected as early as 1-cell and 4-cell stages. In pharyngula period, growth hormone was detected in the otic capsule and forehead region. The result of RT-PCR also showed that growth hormone expression was detected in the mature ovary, somite-stage embryos and hatched larvae. For making growth faster transgenic fish, we transferred a plasmid DNA containing carp b-actin promoter and rainbow rout growth hormone cDNA into farmed ayu by sperm-electroporation method. After five-month culture, the existence of transferred DNA was detected by PCR with specific primers in extracted genomic DNA from caudal fin tissue. The mosaic expressions of transgene were detected from gill, caudal fin, liver, brain and muscle. The growth promotion performance was indicated by 2 fold of body weight and 1.3 fold of body length.