Embryonic signals for skeletal myogenesis: arriving at the beginning.

Embryological studies have identified axial signalling processes that determine somite cells to skeletal myogenesis and control the spatial patterning of muscle differentiation in vertebrate embryos. Gene knockout studies provide evidence that the muscle-specific myoD genes have essential, although partially redundant functions in vivo as regulators of muscle differentiation. However, continuous cell-cell signalling processes also appear to be required to control and maintain the myogenic potential of embryonic progenitor cells, even after activation of myoD genes. The implications of these findings are discussed in relation to cellular mechanisms of muscle regeneration and the use of myoblast transfer as a muscle regeneration therapy.