Moschella M C, Menzies K, Tsao L, Lieb M A, Kohtz J D, Kohtz D S, Taubman M B
The Michael A. and Zena Wiener Cardiovascular Institute, Department of Medicine, The Mount Sinai School of Medicine, New York, NY 10029, USA.
Gene Expr. 1999;8(1):59-66.
SM-20 is a novel, evolutionarily conserved "early response" gene originally cloned from a rat aortic smooth muscle cell (SMC) cDNA library. SM-20 encodes a cytoplasmic protein, which is induced by platelet-derived growth factor and angiotensin II in cultured SMC and is upregulated in intimal SMC of atherosclerotic plaques and injured arteries. We have now examined SM-20 expression during differentiation of cultured skeletal myoblasts and during skeletal myogenesis in vivo. Low levels of SM-20 mRNA and protein were expressed in proliferating mouse C2C12 myoblasts. Differentiation by serum withdrawal was associated with a marked induction of SM-20 mRNA and the expression of high levels of SM-20 antigen in myotubes. The induction was partially inhibited by blocking differentiation with bFGF or TGFbeta. Similar results were obtained with the nonfusing mouse C25 myoblast line, suggesting that SM-20 upregulation is a consequence of biochemical differentiation and is fusion independent. During mouse embryogenesis, SM-20 was first observed at 8.5E in the dermomyotomal cells of the rostral somites. SM-20 expression progressed in a rostral to caudal pattern, with highest levels seen in the muscle primordia and mature muscles. SM-20 thus represents a novel intracellular protein that is regulated during skeletal muscle differentiation and development.
SM-20是一种新的、进化上保守的“早期反应”基因，最初从大鼠主动脉平滑肌细胞（SMC）cDNA文库中克隆得到。SM-20编码一种细胞质蛋白，在培养的SMC中，该蛋白可被血小板衍生生长因子和血管紧张素II诱导，并且在动脉粥样硬化斑块和损伤动脉的内膜SMC中上调。我们现在研究了培养的骨骼肌成肌细胞分化过程中以及体内骨骼肌生成过程中SM-20的表达情况。在增殖的小鼠C2C12成肌细胞中表达低水平的SM-20 mRNA和蛋白。血清饥饿诱导分化与SM-20 mRNA的显著诱导以及肌管中高水平SM-20抗原的表达相关。用碱性成纤维细胞生长因子（bFGF）或转化生长因子β（TGFβ）阻断分化可部分抑制这种诱导。在不融合的小鼠C25成肌细胞系中也得到了类似结果，表明SM-20上调是生化分化的结果，与融合无关。在小鼠胚胎发育过程中，最早在8.5E时在头侧体节的皮肌节细胞中观察到SM-20。SM-20的表达以从头侧向尾侧的模式进行，在肌肉原基和成熟肌肉中水平最高。因此，SM-20代表了一种在骨骼肌分化和发育过程中受到调控的新型细胞内蛋白。
