Origin and migration of neural crest derived cells in the gut

The neurones and glial cells of the enteric nervous system (ENS) are derived from the neural crest (fig 1). While they are migrating, neural crest cells are morphologically indistinguishable from mesenchymal cells through which they migrate, and thus a variety of experimental approaches have been used to examine colonisation of the gut by neural crest derived cells. Yntema and Hammond (1954)1 ablated defined rostrocaudal regions of the neural crest of chicken embryos and examined the effects of the ablations on the ENS. They found that ablation of vagal level (somites 1–7) neural crest resulted in absence of enteric neurones throughout the gut, and therefore concluded that vagal level neural crest is the sole source of the ENS. Following transplantation of vagal level neural tubes from quail embryos into chicken embryos, in which the equivalent region of neural tube had been removed, quail cells were found throughout the gut of the chimera. This also supported the idea that vagal level neural crest cells give rise to enteric neurones throughout the gut.2 However, when the quail neural tube was transplanted into the sacral level (caudal to somite 28) of chicken embryos, quail cells were found within the myenteric plexus of the hindgut of the chimeras, indicating that sacral level neural crest cells also contribute to the ENS in the hindgut.2 Since then, the contribution of sacral level neural crest to the ENS in the hindgut has been controversial. Studies in which explants of chicken gut were removed and grown on the chorioallantoic membrane of host embryos,3 or in which the midgut of chicken embryos was transected prior to the arrival of vagal neural crest cells,4 suggested that either the vagal neural crest cells are the sole source of enteric neurones throughout the gut or that sacral level …