Thibault M C, Zément B
Ontogenesis and Molecular Genetics, Laval University Hospital Center, Sainte Foy, Quebec, Canada.
Med Sci Sports Exerc. 1987 Oct;19(5 Suppl):S134-41.
Muscle genes are developmentally regulated. In vivo, the differential expression of muscle structural genes during myogenesis is controlled in complex ways by extrinsic factors and by a pre-determined genetic program. Terminal differentiation, which is achieved when differentiated myoblasts fuse to form multi-nucleated myotubes, appears mainly regulated by intrinsic factors. Environmental components, on the other hand, play a significant role in the developmental regulation of genes during the course of muscle fiber maturation. In culture, the differential expression of muscle genes is assumed to be solely controlled by intrinsic genetic factors, in the sense that, once precursors cease to proliferate and are committed to become myoblasts, they inevitably progress through terminal differentiation, whatever the environment. The system lacks the necessary elements to proceed towards fiber maturation. Consequently, muscle culture models have, until recently, been limited in studies dealing with the roles played both by genetic and environmental factors in the regulation of muscle gene expression. The accumulating data, however, suggest that under given culture conditions, it is becoming possible to make cells mature beyond embryonic stages and express specific phenotypes in response to extrinsic factors. This paper reviews some of the progress in the development of culture systems which will be useful in studies of muscle plasticity.
肌肉基因受发育调控。在体内，成肌过程中肌肉结构基因的差异表达受外在因素和预先确定的遗传程序以复杂方式控制。当分化的成肌细胞融合形成多核肌管时实现的终末分化，似乎主要受内在因素调控。另一方面，环境因素在肌纤维成熟过程中基因的发育调控中起重要作用。在培养中，肌肉基因的差异表达被认为完全由内在遗传因素控制，也就是说，一旦前体细胞停止增殖并开始成为成肌细胞，无论环境如何，它们都不可避免地经历终末分化。该系统缺乏向纤维成熟发展的必要要素。因此，直到最近，肌肉培养模型在研究遗传和环境因素在肌肉基因表达调控中所起的作用方面仍受到限制。然而，越来越多的数据表明，在特定的培养条件下，使细胞成熟超越胚胎阶段并对外在因素作出反应而表达特定表型已成为可能。本文综述了培养系统发展方面的一些进展，这些进展将有助于肌肉可塑性的研究。
