cDNA CLONING, EXPRESSION AND IMMUNOLOCALIZATION OF GROWTH HORMONE GENE IN ACIPENSER DABRYANUS

The Dabry's sturgeon (Acipenser dabryanus Dumeril, 1868) mainly distributes in the upper Yangtze River of China. It is currently endangered due to the destruction of their spawning grounds and other anthropogenic interferences. In this study, the full-length cDNA sequence of GH was cloned from SMART cDNAs of pituitary in A. dabryanus. The Dabry's sturgeon GH cDNA was 1008 bp in length, including a 52 bp 5'-untranslated region (UTR), a 311 bp 3' UTR and a 645 bp open reading frame (ORF) encoding a peptide of 143 amino acids. Amino acid sequence alignment revealed that A. dabryanus GH shared extremely high identities (over 95%) with its counterparts in other sturgeons. Moreover, sturgeons showed lower GH sequence identities with other bony fish than that of Amphibia, Reptilia, Aves, and Mammalia. By quantitative real-time PCR, GH mRNAs were detected in the pituitary and hypothalamus but absent in any of other somatic organs examined. Moreover, the expression of GH mRNAs in the pituitary was about 110 times to that of hypothalamus. Western-blot analysis suggested the GH expression in both the pituitary and hypothalamus, with higher expression level in the pituitary, which is consistent with the result of qRT-PCR. Immunofluoresence localization showed strong GH-positive signals in the pars intermedia of the pituitary, together with weak fluorescence signals detected in the hypothalamus. HE staining indicated that GH was mainly secreted by eosinophilic cells in the adenohypophysis. This study will benefit both the evolution study of vertebrate GH genes and the further biological function study of GH in cultured A. dabryanus.