Lower skeletal muscle mass in male transgenic mice with muscle-specific overexpression of myostatin
Lower skeletal muscle mass in male transgenic mice with muscle-specific overexpression of myostatin
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DOI：
10.1152/ajpendo.00107.2003
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发表时间：
2003-10-01
影响因子：
5.1
通讯作者：
Gonzalez-Cadavid, NF
中科院分区：
文献类型：
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作者：
Reisz-Porszasz, S;Bhasin, S;Gonzalez-Cadavid, NF
肌肉生长抑制素基因的突变与肌肉增生有关，这表明肌肉生长抑制素抑制骨骼肌的生长。我们推测骨骼肌中肌生长抑制素蛋白的组织特异性表达增加会导致肌肉损失。为了研究这一假设，我们产生了转基因小鼠，过度表达肌肉生长抑制素蛋白选择性地在骨骼肌中，有或没有辅助表达的心脏，利用cDNA构建体，其中野生型（MCK/Mst）或突变的肌肉肌酸激酶（MCK-3E/Mst）启动子被放置在小鼠肌肉生长抑制素cDNA的上游。携带这些MCK启动子连接到增强型绿色荧光蛋白（EGFP）的转基因小鼠仅在骨骼肌和心肌（MCK）或仅在骨骼肌（MCK-3 E）中表达报告蛋白。7周龄的动物通过尾部DNA的PCR或肝脏DNA的Southern印迹分析进行基因分型。通过RT-PCR和Western blot分别测定，MCK/Mst转基因小鼠腓肠肌、四头肌和胫骨前肌中的肌生长抑制素mRNA和蛋白质显著高于野生型小鼠。雄性MCK/Mst转基因小鼠的后肢和前肢肌肉重量比野生型雄性小鼠低18-24%，四头肌和腓肠肌纤维横截面积和肌纤维数量（免疫组织化学）减少18%。MCK-3E启动子突变的雄性转基因小鼠对肌肉质量表现出类似的影响。然而，雌性转基因小鼠与任何类型的MCK启动子没有不同的野生型控制在体重或骨骼肌质量。总之，肌肉生长抑制素在骨骼肌中的表达增加与雄性小鼠中较低的肌肉质量和减少的纤维大小和肌纤维数量、减少的心肌质量和增加的脂肪质量相关，这与其作为骨骼肌质量抑制剂的作用一致。性别特异性的机制仍有待澄清。
Mutations in the myostatin gene are associated with hypermuscularity, suggesting that myostatin inhibits skeletal muscle growth. We postulated that increased tissue-specific expression of myostatin protein in skeletal muscle would induce muscle loss. To investigate this hypothesis, we generated transgenic mice that overexpress myostatin protein selectively in the skeletal muscle, with or without ancillary expression in the heart, utilizing cDNA constructs in which a wild-type (MCK/Mst) or mutated muscle creatine kinase (MCK-3E/Mst) promoter was placed upstream of mouse myostatin cDNA. Transgenic mice harboring these MCK promoters linked to enhanced green fluorescent protein (EGFP) expressed the reporter protein only in skeletal and cardiac muscles (MCK) or in skeletal muscle alone (MCK-3E). Seven-week-old animals were genotyped by PCR of tail DNA or by Southern blot analysis of liver DNA. Myostatin mRNA and protein, measured by RT-PCR and Western blot, respectively, were significantly higher in gastrocnemius, quadriceps, and tibialis anterior of MCK/Mst-transgenic mice compared with wild-type mice. Male MCK/Mst-transgenic mice had 18-24% lower hind- and forelimb muscle weight and 18% reduction in quadriceps and gastrocnemius fiber cross-sectional area and myonuclear number (immunohistochemistry) than wild-type male mice. Male transgenic mice with mutated MCK-3E promoter showed similar effects on muscle mass. However, female transgenic mice with either type of MCK promoter did not differ from wild-type controls in either body weight or skeletal muscle mass. In conclusion, increased expression of myostatin in skeletal muscle is associated with lower muscle mass and decreased fiber size and myonuclear number, decreased cardiac muscle mass, and increased fat mass in male mice, consistent with its role as an inhibitor of skeletal muscle mass. The mechanism of gender specificity remains to be clarified.