Abstract

The phenotype or gene expression of skeletal muscle is largely a consequence of muscle-type specific factors and usage specific factors. An example muscle-type specific factors is seen in the myosin heavy chain (MHC) gene family. MHC the main component of the thick filament of the sarcomere, is encoded by the least 8 different genes each of which produce a MHC isoform of distinct amino acid composition. Four general conclusions about the MHC multigene family have been made by Nadal-Ginard and colleagues. 1) Each muscle expresses more than one MHC gene; 2) each MHC gene, with the exception of the extra-ocular MHC gene, is expressed in moore than one; 3) each adult muscle expresses a distinct set (an average of two) of MHC genes and 4) each genes appears to be under different regulatory programs in different muscles. Thus, it is evident that the control of gene expression is complex. Physical performance or exercise can modulate gene expression in skeletal muscle. We designate these as usage-specific factors of gene expression. Moreover, each type of exercise produces a unique pattern of gene expression. For example, run training results in increased expression of mitochondrial proteins in skeletal muscle while contractile protein is unchanged. On the other hand, weight lifting training increases the expression of both mitochondrial and contractile proteins. Little is known about the mechanisms responsible for these alterations. Verf.-Referat (gekuerzt)