Regional differences between various axial segments of the avian neural crest regarding the formation of enteric ganglia

The vagal neural crest adjacent to somites 1–7 gives rise to the enteric ganglia along the entire digestive tract. It is generally assumed that formation of enteric ganglia in preumbilical gut is independent of the axial segment from which the neural crest originates. In postumbilical gut. however, there is evidence that the axial segment of origin of the neural crest might be relevant to neural differentiation. In this part of the gut, we previously identified a subpopulation of HNK-1-immuno-reactive cells within the enteric mesenchyme. This immunoreactivity disappeared upon formation of the enteric nervous system. We studied the interaction between various axial segments of quail neural crest and the microenvironment in aneural chicken hindgut using chorioallantoic membrane cocultures. We found that neural crest cells from various axial segments could migrate into the gut and home to the correct sites. However, whereas vagal neural crest cells differentiated into enteric neurons, neural crest cells from truncal segments mainly differentiated into melanocytes. The HNK-1-immunore-activity within the enteric mesenchyme only disappeared when neural crest cell colonization was followed by differentiation into enteric neurons and subsequent formation of enteric ganglia. To determine whether differentiation of neural crest cells in chorioallantoic membranc cocultures was influenced by the prolonged presence of the neural tube and notochord, we developed a new coculture system, using neural crest cells cultured in vitro. We found that the differentiation of vagal and trunk neural crest cells within the enteric mesenchyme was not influenced by the prolonged presence of the neural tube and notochord after 24 h. suggesting that there are intrinsic differences between these neural crest cell populations. Upon prolonged in vitro culturing. the properties of vagal neural crest cells changed, and concomitantly, they lost the ability to differentiate into enteric neurons and instead differentiated into melanocytes. We conclude that the disappearance of the HNK-1-immunore-activity within the enteric mesenchyme is correlated with formation of enteric ganglia. In our experimental system. cells from the vagal neural crest are more capable of neural differentiation in the hindgut than cells from other axial levels of the neural crest.