Figure 5.

Expression of myogenic regulatory factors during different stages of satellite cells. Satellite cells are divided into two groups according to their self-renewal ability; myogenic stem (∼10%, PAX7+/Myf5−) and myogenic precursor (∼90%, PAX7+/Myf5+) cells. (A) Myogenic stem cells can undergo asymmetric divisions where some daughter cells return back to quiescence. (B) Myogenic precursor cells undergo symmetrical divisions where all daughter cells are committed to the myogenic fate. Proliferating satellite cells can be identified by the expression of PCNA. Upregulation of MyoD along with the expression of Myogenin and MRF4 induces these cells into the differentiating stage. Terminally differentiated cells may either fuse into pre-existing myofibers, or into newly formed one. Chase ghost act as a scaffold for myogenic stem and precursor cells during activation, proliferation, and differentiation. (A color version of this figure is available in the online journal.)