Skeletal muscle is an area of stem cells study that was previously ignored by stem cell biologists. This is puzzling because skeletal muscle is a tissue that frequently needs to employ stem cells for its maintainence and repair. The major stem cell focus of skeletal muscle is the satellite cell. In addition, it is thought that adult skeletal muscle may be a stem cell niche, directing uncommited cells to be myogenic cells. (7)

What are skeletal muscle fibers?

Skeletal muscle is originally derived from the mesoderm, and is made up of extremely specialized myofibers. These myofibers synchronously contract in order to contract the skeletal muscle. (Take a look at some skeletal muscle) (image from http://www.mds.qmw.ac.uk/biomed/kb/microanatomy/muscle_nerve/) This functional specialization of skeletal muscle is achieved through the process of terminal differentiation, in which cells withdraw from the cell cycle and specific genes are established (and expressed) to define cell identification and function. Post mitotic myofibers are so specialized that they can't proliferate quickly. Therefore, satellite cells are needed. (7)

What are MRF's?

Several MRF's (Myogenic regulatory factors) are present in skeletal muscle such as: MyoD, Myf5, myogenin, MRF4, and desmin. These are important factors in stem cell differentiation into skeletal muscle. (Look at MRF expression on proliferating and differentiating primary myoblasts) (8)