Ability of neural crest cells from the embryonic chick to differentiate into cartilage before their migration away from the neural tube.

Whether neural crest cells from the avian embryo are determined for chondrogenesis before they begin their migration away from the neural tube (i.e., before H. H. stages 8.5--9) was investigated by establishing neural folds from embryos of H. H. stages 5--11 either in organ culture, or as grafts to the chorioallantoic membranes of host embryos. Cartilage differentiated from neural folds taken from embryos of H. H. stages 5--7 but not from those taken from older embryos. This stage specific pattern was reversed when the tissue adjacent to the neural tube was grafted to the chorioallantoic membrane. Cartilage only formed from tissues isolated later than H. H. stage 8; i.e., when these adjacent tissues contain neural crest cells. We concluded that neural crest cells are determined for chondrogenesis while still in the neural tube and before their migration to the face and head. This is in contrast to the situation in the only other group which has been examined, the urodele amphibians.