Schematic of satellite cell myogenesis and markers typical of each stage. Satellite cells are quiescent in normal adult muscle and can be activated by, for example, muscle damage. Once activated, satellite cells divide to produce satellite cell-derived myoblasts that further proliferate, before committing to differentiation and fusing to form myotubes, which then mature into myofibers (for clarity, satellite cell self-renewal is not included). CD34, Pax7, and Myf5/β-gal are expressed in quiescent satellite cells. Satellite cell activation is marked by the rapid onset of MyoD expression, whereas myogenin later marks the commitment to differentiation. The temporal expression pattern of MLC3F-tg is typical of many structural muscle genes such as skeletal muscle actin and MyHC, which mark sarcomeric assembly in the later stages of differentiation. Myf5/β-gal denotes the fusion protein product of the targeted allele of the Myf5nlacZ/+ mouse (Tajbakhsh et al. 1997), whereas MLC3F-tg is the product of the 3F-nlacZ-E transgene (Kelly et al. 1995). (Adapted from Miller et al. 1999 with modifications by J. Beauchamp and the authors.)
Zammit PS, Partridge TA, Yablonka-Reuveni Z.
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