Expression of connexins during differentiation and regeneration of skeletal muscle : functional relevance of connexin 43 Roberto Araya

The formation of skeletal muscle during development occurs via a series of cellular and molecular steps that lead to the formation of multinucleated myofibers. are key regulators in skeletal muscle ontogeny. MyoD and Myf5 are expressed during myogenesis and are markers of commitment to a muscle fiber fate (Braun et al. The onset of the terminal differentiation process is characterized in part by cell cycle withdrawal and myogenin expression. These muscle regulatory factors activate the expression of muscle-specific genes such as the acetylcholine receptor α-subunit (Piette et al., 1990) and creatine kinase (CK) (Lassar et al., 1989). Adult skeletal muscle fibers have the ability to regenerate after injury, a process that in many aspects recapitulates skeletal muscle development. After injury, quiescent mononucleated satellite cells closely associated with injured fibers are activated, leading first to their proliferation and later to cell fusion, culminating in the formation of new myofibers (Grounds et al., 2002). Activation of satellite cells in different injury models is characterized by the expression of MyoD, Myf5, myogenin and MRF4 at early stages after muscle injury (Grounds et al., 1992;