RT Journal Article SR Electronic T1 In vivo satellite cell activation via Myf5 and MyoD in regenerating mouse skeletal muscle JF Journal of Cell Science JO J. Cell Sci. FD The Company of Biologists Ltd SP 2895 OP 2901 VO 112 IS 17 A1 Cooper, R.N. A1 Tajbakhsh, S. A1 Mouly, V. A1 Cossu, G. A1 Buckingham, M. A1 Butler-Browne, G.S. YR 1999 UL http://jcs.biologists.org/content/112/17/2895.abstract AB Regeneration of adult skeletal muscle is an asynchronous process requiring the activation, proliferation and fusion of satellite cells, to form new muscle fibres. This study was designed to determine the pattern of expression in vivo of the two myogenic regulatory factors, Myf5 and MyoD during this process. Cardiotoxin was used to induce regeneration in the gastrocnemius and soleus muscles of heterozygous Myf5-nlacZ mice, and the muscles were assayed for the presence of (beta)-galactosidase (Myf5) and MyoD. Adult satellite cells identified by M-cadherin labelling, when activated, initially express either MyoD or Myf5 or both myogenic factors. Subsequently all proliferating myoblasts express MyoD and part of the population is (beta)-galactosidase (Myf5) positive. Furthermore, we demonstrate that activated satellite cells, which express either Myf5 or MyoD, do not accumulate selectively on fast or slow muscle fibres.