MOLECULAR CLONING AND ANALYSIS OF TWO DISTINCT GROWTH HORMONE cDNAs FROMCAR ASSIUS AURATUS AURATUS

Growth hormone, a 22-kDa single-chain polypeptid e hormone synthesized and secreted by the anterior pituitary gland, plays an impo rtant role in the regulation of growth, development,metabolism and appetite.It is one of the best-studied pituitary hormones that have been used as models for studying of physiology, nutritional composition, regulating of gene expression, structure-function relationships and gene evolution. In mammals,growth hormone variants arising from differential processing of a single primary RNA transcript have been reported, whereas the growth hormone variants found in teleost appear to be the products of different genes.In previous studies, a few teleost fishes h ave two distinct growth hormones, such as chum salmon(Oncorhynchus keta), ch inook salmon (Oncorhynchus tshawytscha), coho salmon(Oncorhynchus kisutch),Atlantic salmon(Salmo salar), rainbow trout (Oncorhynchus mykiss),At lantic cod(Gadus morhua),Japanese eel(Anguilla japonica),goldfish(Car assius auratus),etc.Growth hormone gene duplication was believed to be the re sult of polyploidization among ancestral aquatic vertebrates. There is a close r elationship betweenCarassius auratus auratusand goldfish, belonging to the same family of Cyprinidae.Carassius auratus auratuswere reported to be pol yploid, so it was possible thatCarassius auratus auratusalso had two disti nct growth hormone genes in a single body.Gene duplication was a rare event. Whe ther there were two formsCarassius auratus auratusgrowth hormone cDNAs enc oding distinct growth hormone was still unknown,it was significative to study th e growth hormone polypeptides ofCarassius auratus auratus.