石斑魚（Epinephelus spp.）是台灣主要海水養殖魚類之一，如果可以藉由改造基因促使石斑魚在較短的養殖時間內能長成與傳統養殖型態一樣或更大的結果，就可以降低漁民的養殖成本。抑制肌肉倍增基因 (myostatin) 在牛及老鼠的研究結果，已知能促進肌肉增加。肌肉倍增基因的序列有1131核苷酸，相當於367氨基酸，含有三個重要的基本單元分別為: N端的分泌訊息序列、RXXR 蛋白質水解進行區域及 C 端的半胱胺酸區。而在石斑魚中也有肌肉倍增基因被發現，其氨基酸序列與其它物種的相似度高達70 % 以上，尤其是在C端半胱胺酸區，這部分被認為是肌肉倍增基因的成熟生理活性區域，與其它物種的相似度更高。 Wittemore 等人 (2003) 發現藉由單株抗體來認識並接合在肌肉倍增基因序列中位於C端的15 氨基酸所組成的抗原區，能促進老鼠的肌肉增加。然而，若只利用這個小片段的胜肽來當作抗原，將不易引起免疫反應， 因此利用TR-PCR的技術將這段胜肽之核苷酸序列重複放大並銜接綠濃桿菌外毒素A的domain Ia核苷酸，以此核苷酸序列所表現的嵌合胜肽鏈可提升免疫反應。從石斑魚的實驗顯示出，施打含有六個重複抗原的嵌合抗原的石斑魚，其體重增加量較其它三組為多。因此，抑制肌肉倍增基因，可以增加石斑魚的重量，所以在魚類的肌肉倍增基因可能與哺乳動物的肌肉倍增基因有同樣的功能，因此可以利用抑制肌肉倍增基因的方法，來提高魚的重量，增加生產量。

　　Grouper (Epinephelus spp.) is one of the major high economic aquaculture in Taiwan. Thus, if a gene product can be used of to short the breeding time of groupers and moreover can generate the equal or better quality of groupers than using the traditional breeding, then it will decrease their cost and increase the rate of reproduction. Myostatin is one of genes that can regulate skeletal muscle development and was found in groupers. The full length of myostatin cDNA found in mice and cattle, can cause increase of muscle mass by blocking or mutating this gene. Myostatin cDNA contains 1131 bps nucleotides (i.e. 367 amino acid residues) and myostatin is consist of three critical motifs which are N-terminal signal sequence of secretion、RXXR proteolytic processing site and C-terminal cysteine-rich region. The amino acid sequence of myostatin shows at least 70% conservation among organisms, especially in C-terminal cysteine-rich region which is identified as mature biological active region. Wittemore et al. (2003) developed a neutralizing monoclonal antibody to recognize the epitope of myostatin in mice, which is consisting of 15 amino acids within C-terminal portion of this protein and they found to block this epitope can increase double muscle in mice. But using this small peptide as an antigen may elicit immune response poorly, in order to increase immune response, we construct a gene contain a tandem repeat of this peptide by using TR-PCR technique and conjugated with domain I of pseudomonas exotoxin A. Comparing the muscle weight of groupers using six-copy myostatin epitope antigen with that groupers using one-copy myostatin epitope antigen and using the other two control antigens, PE(Ia) and PBS, we have found that the groupers immunized with the six-copy myostatin antigen has shown more muscle weight increase than others. Thus, inhibiting Myostatin in groupers can cause more muscle weight increase, so it can determine that the function of Myostatin in grouper might be the same function as in mammalian. Moreover, we can use this strategy like inhibiting Myostatin to cause more muscle weight increase and thus decrease fishermen’s cost and increase the rate of reproduction.

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