Evidence in the mouse for self-renewing stem cells in the formation of a segmented longitudinal structure, the myotome.

A novel method of clonal analysis has been used in the mouse to define the cellular events that lead to the formation of a segmented longitudinal structure, the myotome. Progenitor cells of the myotome were randomly marked during development by intragenic homologous recombination in transgenic mice expressing a reporter laacZ gene. 153 clones corresponding to 7829 cells, that is 20% of the myotomal population of one embryo, were obtained from 3000 E11.5 embryos. Their analysis leads to the hypothesis that, at E11.5, the 41 segments of the myotome have been mainly produced from a unique, spatially organised pool of self-renewing stem cells that accompanies the formation of the anterior-posterior axis.