Molecular cloning, characterization and distribution of two types of growth hormone receptor in orange-spotted grouper (Epinephelus coioides)

The cDNAs encoding two distinct growth hormone receptors (GHRs) were firstly cloned and sequenced from the liver of orange-spotted grouper (Epinephelus coioides). The cDNA of grouper GHR1 consisted of 2673-bp and encoded 658 amino acids, while the cDNA of grouper GHR2 consisted of 2989-bp and encoded 577 amino acids. The two cDNAs shared 78.6% identity in nucleotide sequence and 37.8% identity in deduced amino acid sequence. Northern blot analysis demonstrated a single GHR1 transcript of approximately 4.3 kb in liver and a single GHR2 transcript of approximately 3.9 kb in the liver and muscle. In the Real-time PCR assay, grouper GHR1 and GHR2 were expressed in all tissues tested. The expression of GHR2 was significantly higher than that of GHR1 in telencephalon, cerebellum, pituitary, heart and white muscle, whereas the expression of GHR1 was significantly higher in liver. These results indicated that there were two types of GHRs existing in orange-spotted grouper, and they had different structural features and tissues expression patterns. However, the functional differences between GHR1 and GHR2 in orange-spotted grouper remained further research.