Cloning and sequencing of the goldfish growth hormone cDNA

This study cloned a cDNA encoding the mature goldfish growth hormone (gGH) using polymerase chain reaction. The nucleotide sequence of the gGH was greater than 90% homologous to that of common carp, silver carp, bighead carp, and grass carp. The amino acid sequence of gGH, determined based on the nucleotide sequence of its cDNA, showed more than 93% homology to that of other mentioned Cyprinid species, 64% to salmon GH, and 32% to human GH. The cloned gGH was found to lack a cysteine (Cys) residue at position 123 which contrasts with the GH of other Cyprinid species studied to date. The goldfish GH contained only four Cys residues that could be aligned with those of other GHs. This is significant from an evolutionary standpoint, suggesting possible divergence among cyprinids. The cloned gGH cDNA was used as a probe in Northern blotting analysis to investigate the effect of salmon gonadotropin-releasing hormone (sGnRH) on goldfish GH mRNA production in vivo. The results demonstrate for the first time a strong dose-related stimulation of GH synthesis by sGnRH in the goldfish pituitary.