Determination, diversification and multipotency of mammalian myogenic cells

In amniotes, myogenic commitment appears to be dependent upon signaling fro m neural tube and dorsal ectoderm, that can be replaced by members of the W nt family and by Sonic hedgehog, Once committed, myoblasts undergo differen t fates, in that they can differentiate immediately to form the myotome, or later to give rise to primary and secondary muscle fibers. With fiber matu ration, satellite cells are first detected; these cells contribute to fiber growth and regeneration during post-natal life. We will describe recent da ta, mainly from our laboratory, that suggest a different origin for some of the cells that are incorporated into the muscle fibers during late develop ment. We propose the possibility that these myogenic cells are derived from the vasculature, are multi-potent and become committed to myogenesis by lo cal signaling, when ingressing a differentiating muscle tissue. The implica tions for fetal and perinatal development of the whole mesoderm will also b e discussed.