Rainbow trout growth hormone: molecular cloning of cDNA and expression in Escherichia coli

Polymorphisms of the growth hormone gene and their association with growth traits and sex in Sarcocheilichthys sinensis

The growth hormone gene (gh) of Sarcocheilichthys sinensis was cloned and characterized in this study. The cDNA length of gh was 973 bp, containing a 5'-UTR of 15 bp, a 3'-UTR of 325 bp and an open reading frame of 633 bp. The genomic DNA of gh was 2135 bp in length containing five exons and four introns. The precursor peptide of gh contained 210 amino acids (aa), including a signal peptide of 22 aa (Met¹-Ala²²) and a mature region of 188 aa (Ser²³-Leu²¹⁰). The similarity and identity ranges of the gh precursor peptide with those of other cyprinids were 88.6%-99.0% and 84.8%-98.6%, respectively. The gh of S. sinensis expressed at the highest level in the pituitary, and its expression was also detected in muscle and brain. Six polymorphic sites were detected in intron 1 (g.51InDel, g.64InDel and g.242InDel), intron 2 (g.864T>C), intron 3 (g.1017InDel) and intron 4 (g.1541A>G). Among these sites, g.242InDel was significantly associated with condition factor, g.1541A>G was associated with all six growth traits, while g.864T>C was associated with sex. The data obtained herein provide useful information for further studies on the regulation mechanisms of growth and sexual growth differences in S. sinensis.

Effects of recombinant salmon type II growth hormone and bovine growth hormone on growth of coho salmon (Oncorhynchus kisutch)

A comparison of the efficacy of salmon and bovine growth hormone to stimulate growth of coho salmon juveniles was performed. Oncorhynchus nerka (sockeye salmon) type II growth hormone (nGH2) was produced using a bacterial expression system, yielding approximately 25 mg of refolded recombinant protein per litre of cells. The purified nGH2 and bovine growth hormone (bGH) were tested in juvenile O. kisutch (coho salmon) over 24 weeks. Weekly intraperitoneal injections of 0.1 and 0.5 μg/g nGH2 resulted in a dose-dependent increase in weight and fork length compared to control fish injected with bovine serum albumin (BSA). Application of 0.5 μg/g bGH resulted in the same stimulation of growth as did 0.5 μg/g nGH2, indicating these proteins were equipotent. Following 6 weeks of treatment and a subsequent rest period of 7 weeks, coho salmon were further treated with bGH at 0.5 μg/g. A prior treatment with bGH did not reduce growth-promoting activity of bGH in subsequent treatments. Throughout the experiment, condition factor decreased at similar rates for all treatment groups. These data show that bGH, which is widely available, can be used to elevate growth rate in juvenile salmon comparably to homologous GH, and validate the use of bGH in physiological or ecological experiments where rapid growth is desired compared to that seen in wild type.

Effects of growth hormone on leucine absorption, intestinal morphology, and ultrastructure of the goldish intestine

The mechanisms whereby exogenous growth hormone modulates intestinal structure and function in fish were investigated. Goldfish (Carassius auratus) were fed commercial flake diet sprayed with recombinant carp growth hormone (cGH) daily for 1 month. Control animals received food sprayed with the vehicle. After 1 month of daily feedings, body mass and length were determined, and animals were sacrificed to study intestinal characteristics. Sections of foregut were removed after determination of total gut length for measurement of leucine uptake, histology, and epithelial ultrastructure. Oral administration of cGH for 1 month resulted in a 40% increase in body mass and an 8% increase in body length above controls. Gut length was 43% greater and the gut length to body length ratio was 32% greater as a result of the cGH treatment. Feeding with cGH also resulted in a significant increase in leucine uptake and increased gut mucosal thickness. Analysis of transmission electron micrographs revealed significant increases in the microvillous height and density and epithelial surface area. The findings indicate that growth hormone added to feed may increase growth in fish, in part by significantly increasing gut length, mucosal thickness, and epithelial brush border surface area, leading to enhanced epithelial absorption.

Evolution of duplicated growth hormone genes in autotetraploid salmonid fishes

A defining character of the piscine family Salmonidae is autotetraploidy resulting from a genome-doubling event some 25-100 million years ago. Initially, duplicated genes may have undergone concerted evolution and tetrasomic inheritance. Homeologous chromosomes eventually diverged and the resulting reduction in recombination and gene conversion between paralogous genes allowed the re-establishment of disomic inheritance. Among extant salmonine fishes (e.g. salmon, trout, char) the growth hormone (GH) gene is generally represented by two functional paralogs, GH1 and GH2. Sequence analyses of salmonid GH genes from species of subfamilies Coregoninae (whitefish, ciscos) and Salmoninae were used to examine the evolutionary history of the duplicated GH genes. Two divergent GH gene paralogs were also identified in Coregoninae, but they were not assignable to the GH1 and GH2 categories. The average sequence divergence between the coregonine GH genes was more than twofold lower than the corresponding divergence between the salmonine GH1 and GH2. Phylogenetic analysis of the coregonine GH paralogs did not resolve their relationship to the salmonine paralogs. These findings suggest that disomic inheritance of two GH genes was established by different mechanisms in these two subfamilies.

Molecular cloning of growth hormone-encoding cDNA of an Indian major carp, Labeo rohita, and its expression in Escherichia coli and zebrafish

The cDNA clones encoding for growth hormone (GH) of an Indian major carp rohu Labeo rohita were isolated from a cDNA library constructed from the poly(A)(+) RNA extracted from the pituitary glands of rohu. Partial GH cDNA of the rohu (3'-end) was amplified by RT-PCR and used as probe to screen the cDNA library. Full-length GH-specific cDNA clones (1180 bp) were isolated and sequenced. The sequence contains 48-bp 5'-noncoding region followed by an ORF of 621 bp and a 3'-noncoding region of 521 bp. The peptide shares about 90% identity with the GH of Cyprinus carpio (Linn.) and >84% identity with GH sequences of other cyprinids. The GH-encoding cDNA of rohu has been cloned into expression vectors and GH protein has been over expressed in Escherichia coli and purified as a soluble protein. The GH cDNA was cloned into a bicistronic vector with EGFP; injection of in vitro transcribed GH-EGFP mRNA into zebrafish embryo has resulted in EGFP expression confirming the cloned GH cDNA is functional in fish and the IRES element could be effectively used in fish for bicistronic expression of foreign genes.

Cloning, sequencing and expression of cDNA encoding growth hormone from Indian catfish (Heteropneustes fossilis)

A tissue-specific cDNA library was constructed using polyA+ RNA from pituitary glands of the Indian catfish Heteropneustes fossilis (Bloch) and a cDNA clone encoding growth hormone (GH) was isolated. Using polymerase chain reaction (PCR) primers representing the conserved regions of fish GH sequences the 3' region of catfish GH cDNA (540 bp) was cloned by random amplification of cDNA ends and the clone was used as a probe to isolate recombinant phages carrying the full-length cDNA sequence. The full-length cDNA clone is 1132 bp in length, coding for an open reading frame (ORF) of 603 bp; the reading frame encodes a putative polypeptide of 200 amino acids including the signal sequence of 22 amino acids. The 5' and 3' untranslated regions of the cDNA are 58 bp and 456 bp long, respectively. The predicted amino acid sequence of H. fossils GH shared 98% homology with other catfishes. Mature GH protein was efficiently expressed in bacterial and zebrafish systems using appropriate expression vectors. The successful expression of the cloned GH cDNA of catfish confirms the functional viability of the clone.

Stimulation of non-specific immune functions in seawater-acclimated rainbow trout, Oncorhynchus mykiss, with reference to the role of growth hormone

The influence of acclimation to seawater (SW) and growth hormone (GH) administration on immune functions was examined in the rainbow trout (Oncorhynchus mykiss). After 3 days acclimation to dilute SW (12 parts per thousand, ppt), an increase in plasma lysozyme activity was observed compared to the fish kept in fresh water (FW). No change was seen in plasma immunoglobulin M (IgM) levels. When they were transferred from dilute SW to full-strength SW (29 ppt) after a single intra-peritoneal injection of ovine or salmon GH, plasma sodium levels of GH-treated fish were significantly lower than those of the control fish injected with Ringer's solution 24 h after the transfer. The plasma level of IgM was not influenced by GH injection in the fish kept in FW nor in those transferred to SW. The administration of GH increased plasma lysozyme activity in the fish in FW, but no further increase was seen after SW transfer. The production of superoxide anions in peripheral blood leucocytes was stimulated by GH in both FW and SW. These results suggest that GH is involved in the stimulation of the non-specific immune functions in SW-acclimated salmonids.

Isolation, cDNA cloning, and growth promoting activity of rabbitfish (Siganus guttatus) growth hormone

We report the isolation, cDNA cloning, and growth promoting activity of rabbitfish (Siganus guttatus; Teleostei; Perciformes; Siganidae) growth hormone (GH). Rabbitfish GH was extracted from pituitary glands under alkaline conditions, fractionated by gel filtration chromatography on Sephadex G-100, and purified by high-performance liquid chromatography. The fractions containing GH were identified by immunoblotting with bonito GH antiserum. Under nonreducing conditions, the molecular weight of rabbitfish GH is about 19 kDa as estimated by SDS-PAGE. The purified hormone was potent in promoting growth in rabbitfish fry. Weekly intraperitoneal injections of the hormone significantly accelerated growth. This was evident 3 weeks after the start of the treatment, and its effect was still significant 2 weeks after the treatment was terminated. Rabbitfish GH cDNA was cloned to determine its nucleotide sequence. Excluding the poly (A) tail, rabbitfish GH cDNA is 860 base pairs (bp) long. It contained untranslated regions of 94 and 175 bp in the 5' and 3' ends, respectively. It has an open reading frame of 588 bp coding for a signal peptide of 18 amino acids and a mature protein of 178 amino acid residues. Rabbitfish GH has 4 cysteine residues. On the amino acid level, rabbitfish GH shows high identity (71-74%) with GHs of other perciforms, such as tuna, sea bass, yellow tail, bonito, and tilapia, and less (47-49%) identity with salmonid and carp GHs.

Effects of prolactin and growth hormone on plasma immunoglobulin M levels of hypophysectomized rainbow trout, Oncorhynchus mykiss

Immunoglobulin M (IgM) is a major component of the humoral immune system of teleosts. This study examines the effects of hypophysectomy and subsequent replacement with prolactin (PRL) or growth hormone (GH) upon the plasma IgM levels of the rainbow trout (Oncorhynchus mykiss). Plasma IgM levels of the hypophysectomized fish were decreased to 30% of those in sham-operated fish 1 or 4 weeks after operation. Implantation of a cholesterol pellet containing salmon PRL or GH restored plasma IgM levels of the hypophysectomized fish, suggesting important roles for PRL and GH in the regulation of circulating IgM level in trout.

Preparation of recombinant gilthead seabream (Sparus aurata) growth hormone and its use for stimulation of larvae growth by oral administration

Gilthead seabream (Sparus aurata) growth hormone (gsGH) cDNA coding for the mature protein was cloned in a pGEM-T vector and then transferred into prokaryotic expression vector pET-8 and expressed in E. coli BL21 (DE3) cells upon induction with IPTG. 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 over 98% purity, as evidenced by SDS-PAGE. Gel-filtration on a Superdex column under nondenaturing conditions and partial amino acid N-terminal sequence showed the purified protein to be a monomeric alanyl-gsGH. Over 90% pure bacterial beta-lactamase was copurified as a by-product. Binding assays of the [125I]gsGH to gs liver microsomal fraction resulted in high specific binding characterized by a Kd = 1.93 nM. Recombinant gsGH, like ovine placental lactogen, exhibited growth-stimulating activity when applied orally to S. aurata larvae or intraperitoneally to juvenile fish.

Expression of grass carp growth hormone by baculovirus in silkworm larvae

A total of five recombinant Bombyx mori nuclear polyhedrosis viruses (BMNPV) carrying the grass carp (Ctenopharyngodon idellus) growth hormone (GH) cDNA were constructed in this study. Two of them were able to express the hormone up to a level of 12 microgram/ml medium when cultured B. mori cells were infected for 4 days. Inoculation of the viruses into silkworm (B. mori) host significantly increased the level of GH achievable. The amount of hormone produced per larva was estimated to be around 1 mg. The recombinant grass carp GH had immunological and biological activities similar to the native hormone. The N-terminal sequence of the recombinant hormone was the same as the native one, indicating that the fish signal peptide was correctly processed by the insect cells. Silkworm powder prepared from larvae infected with the recombinant virus was used as food supplement for fish. Compared with the control, this dietary supplement was effective in increasing the growth rate of juvenile carp.

Recombinant flounder growth hormone from Escherichia coli: overexpression, efficient recovery, and growth-promoting effect on juvenile flounder by oral administration

An efficient production method for recombinant flounder growth hormone (r-fGH) from Escherichia coli was developed and the biological activity of purified r-fGH was examined using juvenile flounder. The use of bicistronic construction in the expression plasmid resulted in the production of over 40% of the E. coli cellular protein as r-fGH. The r-fGH was recovered from cell lysates following inclusion body washing, solubilization and refolding in sodium dodecylsulfate (SDS) solution, and removal of contaminated proteins with secondary butanol treatment. The SDS content in purified r-fGH solution was adjusted to appropriate levels by diafiltration. More than 47% of the r-fGH was recovered from the E. coli cell lysates and the purity of recovered r-fGH was 98%. The oral administration of purified r-fGH to juvenile flounder, once a week for 4 weeks at a dosage of 40 micrograms r-fGH g-1 fish body weight, resulted in significant increases both in weight and length. These results of overexpression, simple purification with high recovery yield and purity, and good growth-promoting activity of the r-fGH suggest that the production scheme described in this study is useful for the potential application of r-fGH in fish farming.

Highly efficient expression of fish growth hormone by Escherichia coli cells

A PCR product encoding the mature segment of fish pregrowth hormone (pre-GH) was inserted into an Escherichia coli expression vector, pET, in which the ori site was replaced by that of pUC19. The yield of recombinant GH (rGH) was as high as 44 to 47% of total protein. This rGH was immunoreactive to GH antibody. After renaturation, rGH was used to inject fish with 0.1 microgram of rGH per g once every 2 weeks, and this resulted in increases in weight (65%), percent weight gain (165%), and length (22%) relative to those of an untreated control group at week 16 and onward.

Production of a biologically active recombinant teleostean growth hormone in E. coli cells

We have isolated and characterized several recombinant lambda phage clones carrying growth hormone (GH) cDNA of striped bass (Morone saxatilis). Nucleotide sequence and the predicted amino acid sequence of sbGH was determined from a recombinant clone carrying the longest cDNA insert. The sbGH cDNA encodes a pre-hormone of 204 amino acid residues. Comparison of the predicted amino acid sequence of sbGH with those of other vertebrates revealed different degrees of sequence identity: approximately 98% with European sea bass; 90% with bluefin tuna; bonito and red seabream; 71% with winter flounder; 64% with salmonids; 55% with carp; and 38% with human. Expression of the mature sbGH cDNA (without the signal peptide sequence) in E. coli cells under regulation of the lambda phage PL promoter produced a polypeptide of 20 kDa. Following renaturation, this recombinant hormone was shown to be biologically active in a radioreceptor competition binding assay and in the induction of hepatic insulin-like growth factor I (IGF-I) mRNA synthesis in vivo.

Giant catfish Pangasianodon gigas growth hormone-encoding cDNA: cloning and sequencing by one-sided polymerase chain reaction

cDNA clones encoding giant catfish (Pangasianodon gigas) growth hormone (GH) have been isolated using a polymerase chain reaction (PCR) strategy. Pairwise combinations of degenerate and general primers allowed for the amplification of regions both 3' and 5' to the point of entry into the message. The amplified PCR products were cloned and sequenced. The cDNA sequence was found to encode a polypeptide of 200 amino acids (aa), including a putative signal peptide of 22 aa. The 5' and 3' untranslated regions of the message are 58 and 515 nucleotides long, respectively. The giant catfish GH displays the highest aa sequence homology with the carp GH, with 80% of sequence identity. Moreover, giant catfish GH has structural features in common with both mammalian and avian GH polypeptides, and also contains the domains of conserved sequence found in other GH.

Cloning of the sole (Solea senegalensis) growth hormone-encoding cDNA

We report here the complete nucleotide (nt) sequence of a cDNA clone encoding Solea senegalensis growth hormone (sGH) isolated from an expression library prepared from sole pituitary gland poly(A)+RNA. The library was screened using a flounder GH cDNA. The cDNA sequence containing an insert of 769 nt was found to encode a polypeptide of 203 amino acids (aa), including a signal peptide of 17 aa. The 5'- and 3'-untranslated regions of the message are 17 and 119-nt long, respectively. Northern blot hybridization detected a 0.9-kb RNA species. The sGH cDNA sequence shows homologies of 80.9, 76.9, 73.8 and 64.2% with the GH of tuna, gilthead seabream, flounder and rainbow trout.

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

The cDNA encoding the preprotein growth hormone from the dolphinfish (Coryphaena hippurus) has been cloned and sequenced. The cDNA was derived by reverse transcription of RNA from the pituitary of a young fish using the method known as Rapid Amplification of cDNA Ends (RACE). An oligonucleotide primer corresponding to the 5' region of Pagrus major and the universal RACE primer enabled amplification using the Polymerase Chain Reaction (PCR). The dolphinfish and yellow-tail, Seriola quineqeradiata, are both members of the sub-order Percoidei (Perciforme) and their GH sequences show a high level of homology.

Sequence of the growth hormone (GH) gene from the silver carp (Hypophthalmichthys molitrix) and evolution of GH genes in vertebrates

The silver carp (Hypophthalmichthys molitrix) growth hormone (GH) gene was isolated and sequenced following amplification from genomic DNA by the polymerase chain reaction. The gene spans a region of approx. 2.5 kb nucleotides (nt) and consists of five exons. The sequence predicts a polypeptide of 210 amino acids (aa) including a putative signal peptide of 22 hydrophobic aa residues. The arrangement of exons and introns is identical to the GH genes of common carp, grass carp, and very similar to mammals and birds, but quite different from that for the GH genes of tilapia and salmonids. The silver carp GH gene shares a high homology at the nt and aa levels with those of grass carp (95.3% nt, 99.5% aa) and of common carp (81% nt, 95.7% aa).

Molecular cloning and expression of yellowfin porgy (Acanthopagrus latus houttuyn) growth hormone cDNA

1. The growth hormone cDNA of yellowfin porgy (ypGH cDNA) consisted of 915 base pairs. 2. The deduced amino acid (aa) sequence showed that the pre-GH comprised 204 residues, of which the first 17 residues formed a signal peptide. 3. Comparison of aa sequence of ypGH to seabream, tuna, rainbow trout and chum salmon showed that ypGH shared 95.1, 94.1, 65.3 and 62.4% homology with these species, respectively. 4. By expressing the ypGH cDNA in E. coli, a polypeptide around 23 kilodaltons (kDa) was found which was immunoreactive to GH antibody.

Sequence analysis suggests a recent duplication of the growth hormone-encoding gene in Tilapia nilotica

The sequence of two growth hormone(GH)-encoding genes from tilapia fish (Tilapia nilotica) is reported. Our data indicate that the presence of two GH in the tilapia genome is a consequence of a relatively recent duplication event. The two genes are highly homologous, having a similar intron (five)/exon (six) arrangement, and both encode an identical polypeptide. Sequence similarity extends up to bp -628 upstream to the transcription start point, after which the sequences of the two genes are not related to each other. The presence of two GH in the tilapia genome is supported both by the nucleotide sequence and by genomic DNA blot hybridization analysis. Tilapias, like salmonids, contain an extra intron compared with the mammalian GH structure. We suggest that within the superorder Teleostei, the insertion of intron 5 into GH took place after the evolutionary separation of Cyprinoidea, but before Isospondyli (salmonids) and Acanthopterygii (tilapias) were separated. Thus, the additional intron which is probably present in many teleost fish GH may provide an excellent natural marker for evolution and classification studies.

Production of methionyl-minus ovine growth hormone in Escherichia coli and one-step purification

The overproduction of ovine growth hormone (oGH) in Escherichia coli is described, achieved in part by alteration of the codon usage for nine of the first 15 amino acids (aa) of the mature hormone. Recombinant oGH (re-oGH), representing 12% of the total cellular protein, was isolated from inclusion bodies by solubilisation using the cationic surfactant cetyltrimethylammonium chloride (CTAC). The hormone was refolded and subsequently purified to greater than 95% homogeneity in a single step using preparative reverse phase high performance liquid chromatography. The aa sequence analysis revealed that the N-terminus of the E. coli-derived polypeptide was identical to that of pituitary-derived oGH, and re-oGH displayed potent somatotropic activity in vivo.

The primary structures of growth hormones of three cyprinid species: bighead carp, silver carp, and grass carp

The primary structures of growth hormone (GH) of three cyprinid species, bighead carp, silver carp, and grass carp, were determined by a chemical method and/or by molecular cloning. The bighead carp GH was extracted from pituitary tissue by use of an alkaline medium, then successively purified by gel filtration, hydrophobic interaction column chromatography, and reverse-phase high-pressure liquid chromatography. The primary structure of bighead carp GH determined chemically is identical to that deduced from the cDNA nucleotide sequence. By molecular cloning, the primary structures of silver carp and grass carp GHs were also determined. The GHs of these three cyprinid species all contain 188 amino acid residues and their sequences are identical. When four of the five cysteines of cyprinid GHs were arranged to match the same positions of cysteines of other vertebrate GHs, a maximally matched alignment was achieved. Among fishes, GHs are relatively conserved within the same order (82 to 100% identity) but they are more diversified between orders (49 to 68% identity). In further comparison, fish GHs are even more different from tetrapod GHs (37 to 58% identity). Although the primary structures of vertebrate GHs are relatively variable, four homologous sequences, notably one located at the C-terminal, are found.

Primary-structural and evolutionary analyses of the growth-hormone gene from grass carp (Ctenopharyngodon idellus)

The growth-hormone (GH) gene of grass carp, one of the fastest-growing species of farmed fish, was isolated and the DNA sequenced. Only one GH gene is found in this species. This gene, which is 2.5 kb in length, has five exons and four introns, in common with all of the mammalian and the recently published common-carp GH genes. In the course of vertebrate evolution, the total lengths of the intron and the non-coding region of exon 5 of the GH gene have been shortened by 40-70%, whereas the encoding exons of the gene have been slightly increased. The more closely related species exhibit the closest sequence similarity in their GH genes. For example, the similarity of the exons is 84.1-93.2% between grass carp and common carp (within the same family of Syprinedae), 43.5-82.1% between grass carp and rainbow trout (in different orders of Teleostei) and 45.8-58.6% between grass carp and rat (in different grades of Vertebrata). In addition, similar DNA domains, such as thyroid-hormone-receptor-complex-binding site and cell-type-specific cis elements involved in regulation of expression of rat and human GH genes, have been localized in the corresponding regions of the grass-carp GH gene.

The complete amino acid sequence of growth hormone from sturgeon (Acipencer guldenstadti)

The complete amino acid sequence of growth hormone (GH) from a chondrostean species, the sturgeon (Acipencer gludenstaditi), has been determined. Two variants of GH, termed GH I and GH II, were isolated from the pituitary by alkaline extraction, gel filtration on a Sephadex G-100 column, and reversed-phase high-performance liquid chromatography (rpHPLC) on a TSK gel ODS-120T column. The purified proteins were confirmed to be GHs by immunoblotting using bovine and chum salmon GH antisera. For determining of the primary structures, these GHs were digested with lysyl endopeptidase and cleaved with cyanogen bromide. The resulting fragments were separated by rpHPLC and subjected to sequence analysis on an automated gas-phase sequencer employing an Edman method. Both GHs consist of 190 amino acid residues, and contain two disulfide linkages at positions 52-163 and 180-188. The GHs differ from each other at only three positions. Sequence comparison with GHs from other vertebrates revealed that sturgeon GHs have greater sequence homology with tetrapod GHs (63-76%) than with teleost GHs (42-63%).

Cloning and sequencing of the grass carp (Ctenopharyngodon idellus) growth hormone gene

An enriched lambda gt11 library for screening the grass carp (Ctenopharyngodon idellus) growth hormone gene was constructed using HindIII digested genomic DNA extracted from the spleen of the fish. Probing this library with a homologous cDNA, a clone carrying the growth hormone gene was obtained. The gene is 2501 bp long and consists of five exons and four introns. The sequence of nucleotide in the exons is almost identical to that of the cDNA except for ten positions. Analysis of the 5' sequence up to 1220 bp from the +1 position reveals the presence of a TATA box as well as a number of consensus regulatory sequences. Comparison of the grass carp growth hormone gene with those of other fish indicates that there is a high degree of homology with the gene from the common carp but not with those from the rainbow trout and Atlantic salmon.

Primary structure of molluscan metallothioneins deduced from PCR-amplified cDNA and mass spectrometry of purified proteins

The primary structure of metallothioneins (MT) of a mollusc, the oyster Crassostrea virginica, was determined by molecular cloning and mass spectrometry of purified proteins. The cloning strategy included PCR amplification of the responsible cDNAs from total cDNA using completely degenerate oligonucleotides (derived from the N-terminal amino acid sequence) and oligo(dT)20 as primers. Primer extension off mRNA was used as an independent determination of the nucleotide sequence represented by the degenerate PCR primers. The deduced amino acid sequence was consistent with characteristics of class I MT. Twenty-one cysteine residues, were arranged in nine Cys-X-Cys motifs, five as Cys-Lys-Cys. A single Cys-X-X-Cys motif was also observed. Two MTs that differ only in the presence or absence of an N-acetyl group exist in this organism. Masses of tryptic peptides of purified MTs corresponded with those of peptides predicted from tryptic cleavages of the deduced amino acid sequence. Allowing for known N-terminal modifications, 96% of the deduced sequence was confirmed by mass spectrometry. Comparison (FASTA algorithm) of the primary structure of the oyster MTs with those of other species indicated a higher similarity with vertebrate MTs than with those of other invertebrates.

Immunoaffinity purification and partial characterization of sea bass (Dicentrarchus labrax) growth hormone

Growth hormone (GH) was isolated from sea bass (Dicentrarchus labrax) pituitary extract by a simple one-step procedure involving immunoaffinity chromatography. A monoclonal antibody raised against chicken GH and found to immunostain very specifically the GH cells in the pituitary of the sea bass was coupled to CNBr-activated Sepharose 4B. Sea bass pituitary extracts were run on the affinity column, and the eluted material was analyzed on reversed-phase HPLC and found to consist of one single peak. The yield of purified hormone was 2.4 mg/g pituitary. Two monomeric forms (MW = 20,000 and 22,000 Da) of sea bass GH were identified by gel electrophoresis. Gel electrofocusing revealed apparent isoelectric points of 6.15, 6.50, and 6.95. Amino acid composition is consistent with other vertebrate GHs. The immunological relatedness was tested by immunoblotting using antisera raised against GH of different species. Polyclonal antisera raised against the isolated hormone exhibited a specific labeling of the GH cells in sea bass pituitary sections as well as of the immunoblotted purified GH.

Cloning and sequencing of the gilthead seabream (Sparus aurata) growth hormone-encoding cDNA

The cDNA clones encoding gilthead seabream (gsb) (Sparus aurata) growth hormone (GH) have been isolated from a cDNA library prepared from seabream pituitary gland poly(A)+ RNA. The cDNA library was screened using red seabream and rainbow trout GH cDNAs. The complete nucleotide (nt) sequence of gsbGH has been determined. The cDNA sequence codes for a polypeptide of 204 amino acids (aa), including a putative signal peptide of 17 aa. The 5'- and 3'-untranslated regions of the message are 55 and 236 nt long, respectively. The predicted aa sequence of gsbGH revealed 97% homology with red seabream GH, 95% with tuna GH, 85% with yellowtail GH, and 65% with rainbow trout GH.

The development of a noncompetitive enzyme-linked immunosorbent assay for oncorhynchid growth hormone using monoclonal antibodies

The development of a sensitive and specific two-site, or sandwich, noncompetitive enzyme-linked immunosorbent assay (ELISA) for oncorhynchid growth hormone (GH) using monoclonal antibodies (MCAs) is reported. The MCAs were generated by the fusion of myeloma cells with spleen cells from mice that had been immunized with chum salmon (Oncorhynchus keta) recombinant GH. The MCAs specifically recognized the GH-secreting acidophils in the proximal pars distalis of immature male rainbow trout (Oncorhynchus mykiss) pituitaries. Affinity chromatography using one of the MCAs isolated a single protein with a molecular weight of 22,500 from a rainbow trout pituitary extract. The ELISA recognized recombinant chum salmon GH and the affinity-purified protein but did not recognize chum salmon prolactin, gonadotropin I or II, nor several mammalian hormone preparations. The ELISA recognized GH in rainbow trout, coho salmon (Oncorhynchus kisutch), and chinook salmon (Oncorhynchus tshawytscha) pituitary extracts, but not in goldfish (Carassius auratus) extracts, and recognized GH in rainbow trout, coho salmon, lake sturgeon (Acipenser fulvescens), and bowfin (Amia calva) plasma, but not in goldfish, yellow bullhead (Ictalurus natalis), or lamprey (Petromyzon marinus) plasma. The sensitivity of the ELISA was less than 1.56 ng/ml and circulating levels of GH in the plasma of coho salmon and rainbow trout plasma were measured as 75 and 35 ng equivalents/ml, respectively.

Transient expression of foreign DNA during embryonic and larval development of the medaka fish (Oryzias latipes)

Species of small fish are becoming useful tools for studies on vertebrate development. We have investigated the developing embryo of the Japanese medaka for its application as a transient expression system for the in vivo analysis of gene regulation and function. The temporal and spatial expression patterns of bacterial chloramphenicol acetyltransferase and galactosidase reporter genes injected in supercoiled plasmid form into the cytoplasm of one cell of the two-cell stage embryo was promoter-specific. The transient expression was found to be mosaic within the tissue and organs reflecting the unequal distribution of extrachromosomal foreign DNA and the intensive cell mixing movements that occur in fish embryogenesis. The expression data are consistent with data on DNA fate. Foreign DNA persisted during embryogenesis and was still detectable in some 3- and 9-month-old adult fish; it was found in high molecular weight form as well as in circular plasmid conformations. The DNA was replicated during early and late embryogenesis. Our data indicate that the developing medaka embryo is a powerful in vivo assay system for studies of gene regulation and function.

Amino acid sequence of growth hormone isolated from medium of incubated pituitary glands of tilapia (Oreochromis mossambicus)

The amino acid sequence of tilapia (Oreochromis mossambicus) growth hormone (GH) was determined directly by Edman degradation of peptide fragments generated by lysyl endopeptidase and trypsin digestion. The N-terminal residue was deduced to be pyroglutamic acid through the use of pyroglutamyl aminopeptidase; its removal allowed amino acid sequence determination of the remainder of the N-terminal trypsin peptide by Edman degradation. Tilapia GH is composed of 187 amino acid residues and shows high similarity to other perciform GHs. Sequence identities are: 89% with tuna GH, 83% with bonito GH, 85% with yellowtail GH, 89% with red sea bream GH, and 34% with bovine GH. The two asparagine residues (Asn-148 and Asn-184) were recovered by Edman degradation, suggesting the absence of N-glycosylation.

Presence of specific growth hormone binding sites in rainbow trout (Oncorhynchus mykiss) tissues: characterization of the hepatic receptor

The present work outlines the presence of specific binding for chinook salmon growth hormone (sGH) in different tissue preparations of rainbow trout. Optimal incubation conditions (pH, Tris, MgCl2) were determined. Specific binding was very sensitive to salt concentration during incubation. The specific binding reached a plateau after 15 and 25 hr of incubation at 12 and 4 degrees. At 20 degrees, specific and nonspecific binding were not stable. Specific binding dissociation was slower than association and was only partial. The binding was saturable (Bmax = 187 +/- 167 pmol), of high affinity (Ka = 2.4 +/- 0.8 10(9) M-1), and very specific for GH, properties which are in agreement with the characteristics of hormonal receptors. Sea bream and mammalian GH appeared 2- and 30-fold, respectively, less potent than cold sGH2 for displacing 125I-sGH2. Tissue preparations from ovary, testis, fat, skin, cartilage, gill, blood pellet, brain, spleen, kidney, and muscle showed significant saturable binding.

Purification and characterization of Atlantic salmon growth hormone and evidence for charge heterogeneity

Highly purified growth hormone (GH) has been isolated from Atlantic salmon (Salmo salar) pituitaries by extraction with acid acetone, acidic precipitation, and reversed-phase high-performance liquid chromatography (HPLC). The yield was 2.5 mg/g wet tissue. The Atlantic salmon GH (sGH) emerged as a single symmetrical peak after HPLC on a reverse phase C18 column. SDS-gel electrophoresis revealed only one band with an estimated molecular weight of 23,000. Atlantic sGH showed a uniform molecular weight, but two-dimensional (2D) gel electrophoresis of the purified sGH revealed charge heterogeneity with pI's ranging from 6.5 to 8.2. Treatment of the purified sGH with alkaline phosphatase concentrated these different forms into a single more alkaline position (pI 8.2) indicating removal of acidic groups. These results were documented using both silver- and immunostaining of the 2D SDS gels. The purified sGH was phosphorylated in vitro by a calmodulin-dependent protein kinase. Phosphorylation of sGH may be a post-translational modification resulting in several molecular forms with variable acidity. Analysis of the amino acid composition of Atlantic sGH revealed homology with GHs isolated from other teleost species and the amino-terminal sequence showed only three different amino acids within the first 25 residues compared to GH isolated from chum salmon (Oncorhynchus keta) and coho salmon (Oncorhynchus kisutch) pituitaries. Atlantic sGH had a methionine as the amino-terminal residue. Antibodies against chum sGH cross-reacted with Atlantic sGH. Antibodies against either Atlantic or chinook (Oncorhynchus tschawytscha) salmon prolactin or human GH did not cross-react with Atlantic sGH. Atlantic sGH was shown to have a slight growth-promoting activity in the rat tibia assay.

Nucleotide sequence of cDNA and primary structure for hard tail growth hormone

Full-length cDNA for hard tail growth hormone (htGH) has been cloned, and the nucleotide and deduced amino acid sequences have been analyzed. htGH is composed of 188 amino acid residues, and it shows 79, 74, 72, 59, 56, 37, 33 and 30% identity of amino acid with yellow tail, tuna, sea bream, flounder, salmon, blue shark, bullfrog and human GHs, respectively.

Transient expression directed by homologous and heterologous promoter and enhancer sequences in fish cells

In order to construct fish specific expression vectors for studies on gene regulation in vitro and in vivo a variety of heterologous enhancers and promoters from mammals and from viruses of higher vertebrate cells were tested for expression of the bacterial chloramphenicol acetyl transferase reporter gene in three teleost fish cell lines. Several viral enhancers were found to be constitutively active at high levels. The human metallothionein promoter showed inducible expression in the presence of heavy metal ions. A fish sequence was isolated that can be used as a homologous constitutively active promoter for expression of foreign genes. Using the human growth hormone gene with an active promoter in fish cells for transient expression insufficient splicing and lack of translation were observed, pointing to limitations in the use of heterologous genes in gene transfer experiments. On the contrary, some heterologous promoters and enhancers functioned in fish cells as well as in their cell type of origin, indicating that corresponding transcription factors are sufficiently conserved between fish and human over a period of 900 million years of independent evolution.

Gene transfer, expression and inheritance of pRSV-rainbow trout-GH cDNA in the common carp, Cyprinus carpio (Linnaeus)

A recombinant plasmid containing the Rous sarcoma virus-long terminal repeat (RSV-LTR) promoter linked to rainbow trout (Salmo gairdneri) growth hormone (GH) cDNA was microinjected into fertilized carp eggs. Genomic DNA extracted from pectoral fin of individual presumptive transgenic fish was analyzed by dot blot and Southern blot hybridization, using the RSV-LTR and/or the GH cDNA sequences as probes. Out of 365 presumptive transgenic fish analyzed, 20 individuals were found to contain pRSV-rtGH-cDNA sequence in the genomic DNA. Expression of the trout GH polypeptide was detected by immunobinding assay in the red blood cells of nine transgenic fish tested. The level of expression, however, varied among the transgenics and could not be correlated with exogenous DNA copy number. Although there was considerable variation in the sizes of the transgenic fish, those microinjected during the one-cell stage were (P less than 0.05) 22% larger, on the average, than their sibling controls. A randomly selected fraction of the progeny derived from crosses between transgenic males and non-transgenic females inherited the foreign DNA. These transgenic progeny grew faster (P less than 0.05) than their non-transgenic siblings.

Fish as model systems

Fish represent the largest and most diverse group of vertebrates. Their evolutionary position relative to other vertebrates and their ability to adapt to a wide variety of environments make them ideal for studying both organismic and molecular evolution. A number of other characteristics make them excellent experimental models for studies in embryology, neurobiology, endocrinology, environmental biology, and other areas. In fact, they have played a critical role in the development of several of these disciplines. Research techniques that enable scientists to make isogenic lines in a single generation, create and maintain mutants, culture cells, and transfer cloned genes into embryos signal an increasing role for fish as experimental models.

Cloning of the grass carp growth hormone cDNA

We have constructed a cDNA library in lamda gt11 using mRNA isolated from the pituitary glands of the grass carp (Ctenopharyngodon idellus). Based on the published sequence of the rainbow trout growth hormone cDNA, we synthesized two oligonucleotide probes. One of these hybridized strongly with a specific mRNA fragment from the grass carp pituitary. Using this probe, we have isolated six positive clones carrying an insert of approximately 1.2 Kb. By restriction enzyme digestion, all the clones were determined to be identical. Sequence determination on one of them indicated that it has an open reading frame coding for 210 amino acids. Both the nucleotide and translated amino acid sequence are highly homologous to those of the salmon growth hormone and the common carp. A putative signal peptide consisting of hydrophobic amino acids can be identified at the 5' end of the sequence. A polyadenylation signal, ATTAAA, was also present 12 base upstream from the poly A tail.