Developmental potentialities of cells derived from the truncal neural crest in clonal cultures

The developmental potentialities of single truncal neural crest derived cells were analysed in clonal cultures. The clone-forming ability and differentiation potential of crest cells migrating through the somitic mesoderm of 3-day-old embryos (E3) and of non-neuronal cells of dorsal root ganglia taken at E6-14 were compared. Since most of the cells present in the sclerotomal and rostral parts of the somite at E3 become later on incorporated into the spinal ganglia, one can consider that these two cell populations represent the same derivatives of the trunk neural crest at different developmental stages. After 10 days in vitro, the size of clones and their phenotypic composition varied noticeably, revealing a certain heterogeneity in the founder cell populations in terms of developmental potencies. Clones obtained from migrating neural crest cells at E3 were often large (greater than 1000 cells) and many of them contained neuronal and non-neuronal cells. Dorsal root ganglion cells produced mostly small clones (less than 100 cells) in which only non-neuronal (i.e. glial) phenotypes were expressed. Therefore, both the capacity for proliferation and the differentiation ability of cloned neural crest derived cells decrease considerably with increasing embryonic age. This is even more striking if these results are compared with those obtained previously in our laboratory with single cells cultures of E2 cephalic neural crest. In the latter case, both clone sizes and cellular diversity within the colonies were much higher than with E3 truncal crest and dorsal root ganglia (DRG) non-neuronal cells. The second result of the present work concerns the differentiation of the dormant autonomic neuronal precursors of the DRG. It has been established previously that the non-neuronal cells of the DRG include adrenergic precursors than can differentiate in mass culture of dissociated DRG cells. We show that these cells never differentiate in clonal cultures but depend upon the cell density of the culture. This suggests that cell to cell interaction between crest derived cells are critical in eliciting the differentiation of the adrenergic phenotype.