Cloning and sequencing of dolphinfish (Coryphaena hippurus, Coryphaenidae) growth hormone-encoding cDNA

Cloning and biological analysis of the zebrafish (Danio rerio) insulin-like growth factor binding protein-2 proximal promoter region

Insulin-like growth factor binding protein 2 (IGFBP-2) plays an important role in the regulation of IGF's action and endocrinology in fish. To understand the molecular mechanism which controls transcription of the IGFBP-2 gene, we cloned and sequenced the IGFBP-2 proximal promoter region of the zebrafish IGFBP-2 gene and characterized its activity by firefly luciferase transient transfection expression assays. Different fragments of the zebrafish IGFBP-2 5'-flanking region were transfected into Hela and ZFL cells. In these cell lines, maximum promoter activity was located in the 900 base pairs (bp) of the zebrafish IGFBP-2 5' flanking region in the ZFL cell line and 318 bp of the zebrafish IGFBP-2 5' flanking region in the Hela cell line. The in vivo actions of the IGFBP-2 promoter on developmental stage expression were further investigated in transgenic zebrafish in which an IGFBP-2 (900-bp) promoter-driven green fluorescent protein encoding the GFP cDNA transgene was microinjected into zebrafish embryos. Morphological and RT-PCR studies of transgenic zebrafish indicated that the IGFBP-2 promoter-driven GFP transcripts appeared for the first time in the 32-cell stage. These results indicate that the IGFBP-2 promoter is active in a development-specific manner. These results suggest that the IGFBP-2 promoter plays an important role in teleost embryo growth.

Preparation and characterization of recombinant dolphin fish (Coryphaena hippurus) growth hormone

Dolphin fish (Coryphaena hippurus) growth hormone (dfGH) cDNA encoding the mature protein was cloned in a pET11a expression vector and expressed in Escherichia coli BL21 cells upon induction with isopropyl-1-thio-beta-d-galactopyranoside as an insoluble protein. The expressed protein, contained within the inclusion-body pellet, was solubilized in 4.5 M urea, refolded at pH 11.3 in the presence of catalytic amounts of cysteine, and purified to homogeneity, as evidenced by SDS-PAGE. Gel filtration on a Superdex column under nondenaturing conditions and amino-terminal analysis showed the purified protein to be monomeric methionyl-dfGH. Binding assays of the (125)I-labeled dfGH to dolphin fish liver microsomal fraction resulted in high specific binding characterized by a K(a) of 0.77 nM(-1) and a B(max) of 285 fmol/mg microsomal fraction protein. The purified dfGH was capable of stimulating proliferation of FDC-P1-B9 cells transfected with rabbit growth hormone (GH) receptor. The maximal effect of dfGH was identical to that of human GH but their respective EC(50) values were 28 nM versus 0.095 nM.

Isolation and characterization of tilapia (Oreochromis mossambicus) insulin-like growth factors gene and proximal promoter region

To understand the molecular mechanism which controls the transcription of the insulin-like growth factors (IGFs) gene, we have cloned and sequenced the cDNA for the proximal promoter region of the tilapia IGFs gene and have characterized its activity by chloramphenicol acetyltransferase (CAT) transient transfected expression assays. Tilapia (Oreochromis mossambicus) IGF-I cDNA (549 bp) was amplified by PCR from single-stranded cDNA of growth hormone (GH)-induced liver RNA using a pair of oligonucleotides specific for fish IGF-I as amplification primers. Tilapia IGF-I and IGF-II 5' termini were analyzed by rapid amplification of cDNA 5' ends (5'RACE). Analysis of the 5'RACE results revealed two transcription start sites in IGF-I and one transcription start site in IGF-II. Different fragments of the 5' flanking region were transfected into human lung adenocarcinoma cells. In the cell line, maximum promoter activity was located in the distal 657 basepairs of the IGF-I 5' flanking region and in the distal 450 basepairs of the IGF-II 5' flanking region. The in vivo actions of the IGFs promoter on developmental stage expression were investigated further in transgenic zebrafish in which an IGFs promoter-driven green fluorescent protein (GFP) encoding the cDNA transgene was microinjected into embryos. Morphologic and RT-PCR studies of the transgenic zebrafish indicated that IGF-I promoter-driven GFP transcripts appeared for the first time in the 1-K-cell stage and the IGF-II promoter-driven GFP transcripts appeared for the first time in the 32-cell stage. Fluorescent (GFP) distribution was apparent within 48 h in IGF-II-transgenic zebrafish embryos, especially in eye, muscle, corpuscle, floor plate, horizontal myoseptum, yolk sac extension, and yolk sac. These results indicate that the IGF-I and IGF-II promoters are active in tissue and in a development-specific manner. Our findings also indicate that the IGF-II promoter influences the growth of fish embryos earlier than does IGF-I, and IGF-II has higher levels of expression than does IGF-I. These results suggest that the IGF-II promoter plays a growth factor role in teleost embryo development.