2 Retrospective Tracing of the Developmental Lineage of the Mouse Myotome

Publisher Summary This chapter discusses the method of clonal analysis to study cellular events that lead to the formation of the muscle and the central nervous system. From a theoretical view, this method has similarities with genetic mosaics obtained from aggregation chimeras and from retroviral labeling but has the additional advantage of restricting the analysis to a class of cells or to a territory. More importantly, the random nature of the labeling event at the origin of the clones allows for a complete description of any ancestral cell of a structure, because cells can be marked at virtually all stages of development. The proposition of a stem cell system at the origin of the paraxial mesoderm is reminiscent of observations regarding the persistence of cells in the anterior part of the primitive streak. The retrospective clonal analysis described in this chapter has amplified these findings by permitting long-term studies and, therefore, an evaluation of the consequences of very early events on a differentiated structure. The analysis reveals the persistence of stem cells throughout axiogenesis.