Chapter 3 Molecular Aspects of Myogenesis * *This text was assembled from separate parts written by the individual authors. We apologize for the resulting inconsistency of style. the order of authorship was chosen at random.

This chapter discusses the relevant literature in only those areas of myogenesis that deal with the quantitative and qualitative changes in protein synthesis, accompanying the terminal steps of muscle cell differentiation and the molecular mechanisms controlling these changes. Embryonic muscle cell cultures offer many unique advantages in the study of genetic expression during terminal differentiation: (1) two basic cell populations are distinguishable; one that expresses the specialized muscle phenotype and the precursor to this population that expresses no apparent muscle function. (2) These two populations are separable in time, precursors being abundant early in culture and muscle cells arising afterward, with a relatively synchronous transition between the two. (3) Passage from the precursor to the muscle cell is followed or accompanied, by a dramatic morphological event, that of the cell fusion and fiber formation. (4) Gene expression in the developing cells can perhaps be modulated by a host of external factors, including innervations. Apart from the morphological criterion of cell fusion, one of the attractive features of cultured muscle cells is the facility they offer for measuring the synthesis and accumulation of proteins normally associated with muscle tissue.