Growth hormone and two forms of insulin-like growth factors I in the giant grouper (Epinephelus lanceolatus): molecular cloning and characterization of tissue distribution

Abstract

Growth hormone and insulin-like growth factors play important roles in the growth, development and metabolism of vertebrates. In this study, we used reverse transcription and rapid amplification of cDNA ends (RACE) to obtain the three full-length cDNA sequences encoding GH and two forms of IGF-I from the giant grouper (Epinephelus lanceolatus), a coral fish of high commercial value cultured in Southeast Asia. GH precursor cDNA consists of 938 bp in size with an open-reading frame (ORF) encoding 204 amino acid (aa), a 65 bp 5'-untranslated region and a 236 bp 3'-untranslated region. The sequence of giant grouper GH shared 98.6% nucleotide sequence homology with orange-spotted grouper (E. coioides) GH. Two forms of IGF-I precursor cDNA were cloned from giant grouper, IGF-I a consisting of 159 aa, and IGF-I b with 186 aa. They shared 98.4 and 98.7% aa identity with IGF-I reported in the orange-spotted grouper, respectively. Giant grouper IGF-I a and b have the same signal peptide and B-C-A-D domains, but they are different in the E domain. Using real-time reverse transcription PCR strategy, tissue distribution profile showed that GH and IGF-I mRNA signals were all observed in pituitary, brain, liver, ovary and spleen. GH mRNA in pituitary was the most abundant, and IGF-I mRNA level in liver was found to be more abundant than that in other selected tissues. These findings will contribute to the understanding of the evolution of GH and IGF-I, and provide some basic information about the characterization of GH and IGF-I in the giant grouper.