THE COMPARATIVE EXPRESSION AND CROSS-INTERACTIONS OF GROWTH HORMONE/PROLACTIN LIGAND AND RECEPTOR FAMILY MEMBERS IN ZEBRAFISH EARLY EMBRYOS

Growth hormone (GH) is a member of the GH/Prolactin (PRL) protein super family. It is secreted by anterior pituitary and critically involved in the regulation of cell proliferation, differentiation and migration. Using RT-PCR (re-verse-transcription PCR), our previous study revealed that both gh and its receptor gene ghra (growth hormone receptor a) were maternally expressed in zebrafish. This suggested that the GH/GHR signaling pathway might play an important role at the early stage of zebrafish development. To further study the function of GH/PRL signaling pathway in zebrafish embryogenesis, here we characterized and compared the expression patterns of gh/prl and their receptor family members in early embryonic development using real-time PCR and in situ hybridization. We found that the ligand family members, gh and somatolactin (smtl), and the receptor gene family members, ghra and ghrb, were maternally expressed in zebrafish. The analysis of spi2.1 promoter activity indicated the cross-interaction between various ligand family members and GHRa in the early embryos of zebrafish. Our results demonstrated the important role of the GH/PRL family signaling pathway in the early development of zebrafish.