Analysis of gene expression regulating differentiation of slow and fast muscle fibers

骨骼肌由慢肌纤维和快肌纤维组成，它们具有不同的生理生化特性。慢速肌纤维和快速肌纤维的相对比例是决定骨骼肌收缩速度和疲劳性的重要因素。为了研究肌纤维的分化，我们首先研究了小鼠和大鼠骨骼肌中肌纤维类型的组成。结果表明，存在一组骨骼肌，其中含有极丰富的慢肌纤维，可用于研究慢肌纤维基因表达。利用富含慢纤维的比目鱼肌和富含快纤维的胫前肌制备的cDNA，通过与DNA阵列（Agilent co . ltd .）的竞争杂交检测了基因表达谱，并通过15只大鼠骨骼肌制备的cDNA面板验证了差异表达基因的纤维类型特异性，确定了肌纤维组成。在比目鱼肌和胫前肌之间，大约有500多个基因的表达水平存在两倍以上的差异。70个基因编码代谢途径中的酶，如糖酵解或脂解，45个基因编码结构蛋白，80个基因编码转录因子和/或信号转导。除了这些已知的基因外，我们还发现了比目鱼肌和胫骨前肌之间250个未知基因的差异。为了研究这些基因差异表达的生物学相关性，我们在膝关节水平切断胫骨神经和腓总神经，以诱导肌肉萎缩和肌纤维去分化。人们认为，去神经支配会诱导肌纤维从慢向快的转化，从而使慢肌纤维和快肌纤维的基因表达谱变得相似。然而，在去神经支配一个月后，比目鱼肌和胫前肌之间仍然存在实质性差异。这些结果表明，肌纤维保留了部分特定于其原始分化状态的基因表达谱，甚至失去了对神经的控制。少

Skeletal muscles consist of slow-twitch and fast-twitch muscle fibers, which have distinct physiological and biochemical properties. The relative proportion of slow and fast muscle fibers is an important factor determining the contractile velocity and fatigability of skeletal muscle. To investigate the differentiation of muscle fibers, we first examine the composition of myofiber types in mice and rats skeletal muscles. It revealed that there was a group of skeletal muscles, which were extremely rich in slow muscle fibers and useful to study gene expression in slow muscle fibers.Using cDNA prepared from the slow fiber-rich soleus muscle and the fast fiber-rich tibialis anterior muscle, we examined the gene expression profile by competitive hybridization to a DNA array (Agilent co ltd), and verified fiber-type specificity of differentially expressed genes by the cDNA panel prepared from 15 rat skeletal muscles, whose myofiber composition was determined. About more than 500 genes showed … More two-fold difference in their expression levels between the soleus and the tibialis anterior muscles. Seventy genes encode enzymes in metabolic pathways, such as glycolysis or lipolysis, 45 genes for structural proteins, 80 genes for transcription factors and/or signal transducers. Besides these known genes, we found the difference in 250 unknown genes between the soleus and the tibialis anterior muscles. To study the biological relevance of differential expression of these genes, we cut the tibialis and common peroneal nerves at the level of knee joints to induce muscle atrophy and dedifferentiation of myofibers. It has been postulated that denervation would induce slow to fast conversion of muscle fibers, thereby gene expression profiles of slow and fast muscle fibers become resembling. However, substantial difference remained between the soleus and tibialis anterior muscles one month after denervation. These results suggest that myofibers kept a part of gene expression profile specific to their original differentiation state, even loosing their nervous control. Less