Coleman M E, DeMayo F, Yin K C, Lee H M, Geske R, Montgomery C, Schwartz R J
Department of Cell Biology, Baylor College of Medicine, Houston, Texas 77030, USA.
J Biol Chem. 1995 May 19;270(20):12109-16. doi: 10.1074/jbc.270.20.12109.
The avian skeletal alpha-actin gene was used as a template for construction of a myogenic expression vector that was utilized to direct expression of a human IGF-I cDNA in cultured muscle cells and in striated muscle of transgenic mice. The proximal promoter region, together with the first intron and 1.8 kilobases of 3'-noncoding flanking sequence of the avian skeletal alpha-actin gene directed high level expression of human insulin-like growth factor I (IGF-I) in stably transfected C2C12 myoblasts and transgenic mice. Expression of the actin/IGF-I hybrid gene in C2C12 muscle cells increased levels of myogenic basic helix-loop-helix factor and contractile protein mRNAs and enhanced myotube formation. Expression of the actin/IGF-I hybrid gene in mice elevated IGF-I concentrations in skeletal muscle 47-fold resulting in myofiber hypertrophy. IGF-I concentrations in serum and body weight were not increased by transgene expression, suggesting that the effects of transgene expression were localized. These results indicate that sustained overexpression of IGF-I in skeletal muscle elicits myofiber hypertrophy and provides the basis for manipulation of muscle physiology utilizing skeletal alpha-actin-based vectors.
禽骨骼肌α-肌动蛋白基因被用作构建成肌表达载体的模板，该载体用于指导人IGF-I cDNA在培养的肌肉细胞和转基因小鼠的横纹肌中的表达。禽骨骼肌α-肌动蛋白基因的近端启动子区域，连同第一个内含子和1.8千碱基的3'-非编码侧翼序列，在稳定转染的C2C12成肌细胞和转基因小鼠中指导人胰岛素样生长因子I（IGF-I）的高水平表达。肌动蛋白/IGF-I杂交基因在C2C12肌肉细胞中的表达增加了成肌碱性螺旋-环-螺旋因子和收缩蛋白mRNA的水平，并增强了肌管形成。肌动蛋白/IGF-I杂交基因在小鼠中的表达使骨骼肌中的IGF-I浓度提高了47倍，导致肌纤维肥大。转基因表达未增加血清中的IGF-I浓度和体重，表明转基因表达的影响是局部的。这些结果表明，骨骼肌中IGF-I的持续过表达引发肌纤维肥大，并为利用基于骨骼肌α-肌动蛋白的载体操纵肌肉生理学提供了基础。
