A myogenic precursor cell that could contribute to regeneration in zebrafish and its similarity to the satellite cell

The cellular basis for mammalian muscle regeneration has been an area of intense investigation over the last few decades. Consensus has been reached that a specialized self-renewing stem cell termed the satellite cell plays the major role during the process of regeneration in amniotes. How broadly deployed this mechanism is within the vertebrate phylogeny remains an open question. This lack of information on the role of analogous cells to the satellite cell in other vertebrate systems is even more surprising given the fact that that satellite cells were first designated in frogs. An intriguing aspect of this debate is the fact that a number of amphibia and many fish species have been shown to exhibit epimorphic regenerative processes in specific tissues, whereby regeneration occurs by the dedifferentiation of the damaged tissue itself, and does not deploy specialized stem cell populations analogous to satellite cells. Hence it is feasible that a cellular process completely distinct to that deployed during mammalian muscle regeneration could operate in species capable of epimorphic regeneration. In this review we examine the evidence for or against the broad phylogenetic distribution of satellite cells. We conclude that in the vertebrates so far examined, epimorphosis does not appear to be deployed during muscle regeneration, and that analogous cells expressing similar marker genes to satellite cells appear to be deployed during the regenerative process. However, the functional definition of these cells as self-renewing muscle stem cells remains a final hurdle to the definition of the satellite cell as a generic vertebrate cell type. This article is protected by copyright. All rights reserved.