FIGURE 1.

Scheme of the satellite cell myogenic program. SCs are normally in quiescence and enter a myogenic cycle upon stress conditions such as injury. In the steady-state, they express Pax7. Activation of SCs can be determined by the co-expression of Pax7 and the myogenic regulatory factor MyoD. Proliferating SCs later differentiate into differentiated/committed progenitors characterized by the downregulation of Pax7 expression and the induction of Myog expression. These differentiated cells will eventually fuse into myofibers. A subset of the proliferating SCs will return to quiescence through the process of self-renewal.