Absence of neural crest cell regeneration from the postotic neural tube

The preotic neural tube has a variable ability for regeneration of neural crest depending on the neuraxial level. There is robust regeneration of neural crest in the caudal midbrain/rostral hindbrain. In contrast, removal of the cardiac neural crest results in cardiovascular abnormalities suggesting the lack of regeneration in this area, although the regenerative capacity of the cardiac crest region has never been tested directly. Premigratory cardiac neural crest was ablated bilaterally using laser irradiation or extirpation by tungsten needle, and the remaining ventral neural tube was labeled with DiI to examine any neural crest regeneration from the neural tube. The results indicate that there is very little regeneration of crest cells from the cardiac region of the neural tube if the ablation is done prior to the 5-somite stage and no regeneration after the 6-somite stage with either ablation procedure. Furthermore no compensatory response occurs from the adjacent regions of the neural crest. By contrast, we were able to confirm that regeneration of neural crest occurs in the preotic rhombencephalic neural tube even after laser irradiation. An analysis in the trunk region suggests that the trunk neural tube is similar to the cardiac region in that it does not regenerate crest cells in the ventral migratory pathway after ablation. However, melanocytes generated cranial and caudal to the ablated region migrate radially and fill in the ablated region 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 tube does not have such regenerative ability.