ABSENCE OF NEURAL CREST CELL REGENERATION FROM THE POSTOTIC NEURAL-TUBE

The preotic neural tube has a variable ability for regeneration of neu ral crest depending on the neuraxial level. There is robust regenerati on of neural crest in the caudal midbrain/rostral hindbrain. In contra st, removal of the cardiac neural crest results in cardiovascular abno rmalities suggesting the lack of regeneration in this area, although t he regenerative capacity of the cardiac crest region has never been te sted directly. Premigratory cardiac neural crest was ablated bilateral ly using laser irradiation or extirpation by tungsten needle, and the remaining ventral neural tube was labeled with DiI to examine any neur al crest regeneration from the neural tube. The results indicate that there is very little regeneration of crest cells from the cardiac regi on of the neural tube if the ablation is done prior to the 5-somite st age and no regeneration after the 6-somite stage with either ablation procedure. Furthermore no compensatory response occurs from the adjace nt regions of the neural crest. By contrast, we were able to confirm t hat regeneration of neural crest occurs in the preotic rhombencephalic neural tube even after laser irradiation. An analysis in the trunk re gion suggests that the trunk neural tube is similar to the cardiac reg ion in that it does not regenerate crest cells in the ventral migrator y pathway after ablation. However, melanocytes generated cranial and c audal to the ablated region migrate radially and fill in the ablated r egion so that there is no interruption of the normal pigment pattern. This study indicates that even though there is a variable capacity for crest regeneration in the preotic neural tube, the postotic neural tu be does not have such regenerative ability. (C) 1997 Academic Press.