A common somitic origin for embryonic muscle progenitors and satellite cells

A new population of stem cells, present in skeletal muscle, has been identified in two independent studies. The cells are important in the formation of skeletal muscle in the embryo and fetus. The origin of early embryonic muscle cells is well understood, but less is known about the later stages, where progenitor cells in the muscle mass continuously form new cells in the fetus. Relaix et al. identify cells in mice that continue to proliferate in the trunk and limbs during development. These cells express the transcription factors Pax3 and Pax7, the absence of which causes later muscle development to fail. Gros et al. trace lineage in the chick to show that the origin of this cell population is in a region of the embryo called the somite, and that these cells give rise to satellite cells — the committed stem cells of adult skeletal muscle. Greater understanding of the origin of muscle cells may help in developing therapies to combat muscle disease.