Gene expression in skeletal muscle.
Muscle has an intrinsic ability to change its mass and phenotype in response to activity. This process involves quantitative and qualitative changes in gene expression, including that of the myosin heavy chain isogenes that encode different types of molecular motors. This, and the differential expression of metabolic genes, results in altered fatigue resistance and power output. The regulation of muscle mass involves autocrine as well as systemic factors. We have cloned the cDNAs of local and systemic isoforms of insulin-like growth factor-I (IGF-I) from exercised muscle. Although different isoforms are derived from the IGF-I gene by alternative splicing, the RNA transcript of one of them is only detectable following injury and/or mechanical activity. Thus this protein has been called mechano growth factor (MGF). Because of a reading-frame shift, MGF has a different 3' sequence and a different mode of action compared with systemic or liver IGF-I. Although MGF has been called a growth factor, it may be regulated as a local repair factor.
Goldspink
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Departments of Anatomy and Surgery, Royal Free and University College Medical School, Royal Free Campus, University of London, Rowland Hill Street, London NW3 2PF, U.K. goldspink@rcf.ucl.ac.uk
D000818:Animals; D001696:Biomechanical Phenomena; D015870:Gene Expression; D006133:Growth Substances / Q000235:genetics / Q000378:metabolism; D006801:Humans; D006984:Hypertrophy; D007334:Insulin-Like Growth Factor I / Q000235:genetics / Q000378:metabolism; D018485:Muscle Fibers, Skeletal / Q000378:metabolism; D018482:Muscle, Skeletal / Q000254:growth & development / Q000378:metabolism* / Q000473:pathology; D010641:Phenotype
D006133:Growth Substances; D007334:Insulin-Like Growth Factor I