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

Growth hormone from striped catfish (Pangasianodon hypophthalmus): genomic organization, recombinant expression and biological activity

Growth hormone is an essential polypeptide required for normal growth and development of vertebrates. In this report, striped catfish (Pangasianodon hypophthalmus) growth hormone gene and cDNA were isolated by reverse transcriptase-polymerase chain reaction. The striped catfish growth hormone (scGH) encoding gene contains 5 exons and 4 introns. The cDNA sequence of the scGH gene contains a 603bp open reading frame and encodes for a 200-aa protein consisting of a putative 22-aa signal peptide and the mature 178-aa protein. The recombinant histidine-tagged scGH protein which expressed in Escherichia coli as inclusion bodies was unfolded, refolded and purified to near-homogeneity by Ni(2+)-NTA chromatography. Analysis of the secondary structure content by CD spectroscopy showed that the α-helical content of the refolded scGH is 55%. Elucidation of the folding pathway of scGH by fluorescence spectroscopy showed that denaturation transition of scGH is coincident and cooperative, consistent with the two-state denaturation mechanism. The purified scGH was biologically active and exhibited growth-promoting activity in striped catfish, but not tilapia.

[cDNA cloning and protein structure analysis of growth hormone from Clarias lazera]

Total RNA was isolated from pituitary gland of Clarias lazera, and the cDNA encoding growth hormone (GH) protein was amplified and cloned by reverse transcription polymerase chain reaction (RT-PCR). The open reading frame (ORF) of cDNA is of 603 nt which encodes GH precursor consisted of a signal peptide with 22 amino acid residues and a mature peptide with 178 amino acid residues. Sequence alignment indicated that the amino acid sequence homology approached to 95.8% between C. lazera and other 6 species of Siluriforms catfish. Secondary structure assessment showed that the GH protein contained different structural regions of alpha-helix, beta-sheet, beta-turn and random coil, among which alpha-helix has main proportion. Antigenicity analysis indicates that there exist 4 domains in amino acid sequence where B cell dominant epitopes could form. Summarily, the structure characteristics of C. lazera GH should provide a great benefit in its modification into recombinant vaccine or monoclonal antibody for future application.

Molecular cloning of growth hormone encoding cDNA of Indian major carps by a modified rapid amplification of cDNA ends strategy

A modified rapid amplification of cDNA ends (RACE) strategy has been developed for cloning highly conserved cDNA sequences. Using this modified method, the growth hormone (GH) encoding cDNA sequences of Labeo rohita, Cirrhina mrigala and Catla catla have been cloned, characterized and overexpressed in Escherichia coli. These sequences show 96-98% homology to each other and are about 85% homologous to that of common carp. Besides, an attempt has been made for the first time to describe a 3-D model of the fish GH protein.

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.