REGULATION OF MYOGENESIS

Molecular-biological and molecular-genetic mechanisms underlying regul ation of muscle formation were analyzed from the earliest Stages of co mmitment and determination of myogenic precursors to the terminal stag es of muscle differentiation. It was shown how inductive influences of the neural tube and notochord on the somites leading to formation of myotomes are related to expression of genes of the Shh and Wnt familie s. Differentiation of proliferating myoblasts and myotubes is related to expression of the genes encoding synthesis of bHLH proteins: MyoD a nd Myf5 in the myoblasts and myogenin and MRF4 in the myotubes. The pr oducts of these genes are transcription factors and control the subseq uent stages of myogenesis, specifically, myogenin controls expression of the genes of contractile proteins. Changes in the spectra of contra ctile proteins during ontogenesis and diversity of their isoforms are related both to the expression of various genes and to their alternati ve splicing. The mechanisms underlying the assembly of myofibrils in o ntogenesis, which involve, in addition to myosin and actin, proteins o f Z-bands and A-discs, were analyzed.