Restrictions of developmental capabilities in neural crest cell derivatives as tested by in vivo transplantation experiments

The behavior of neural crest cells from various origins and of neural crest derivatives were investigated when they were transplanted into a host embryo as supernumerary crest structures. They were inserted into the dorsal trunk between the neural primordium and the somites. In this situation the grafted cells (of quail origin) migrated in the chick host and could be recognized any time after the graft by the structure of their nucleus. After a migration phase, they became exclusively localized in the various sites of arrest of neural crest cells and were found mixed with host crest cells. Their localizations varied according to their origin and their developmental stages at grafting time. Cells of autonomic ganglia (ciliary and sympathetic) had a definitive localization restricted to the autonomic structures of the host. They differentiated into adrenergic or cholinergic cells irrespective of their sympathetic or parasympathetic origin, according exclusively to their localization in the host. They were practically never found in the host dorsal root ganglion (DRG). In contrast, the developmental potentialities of DRG cells are broader and, as far as peripheral nervous system potentialities are concerned, they behave like neural crest cells, i.e., they gave rise to both sensory and autonomic neurones plus adrenomedullary cells. A model for cell line segregation from the neural crest is proposed. Several aspects of this model need further analysis, others are based on well-established experimental data.