In ovo time-lapse analysis after dorsal neural tube ablation shows rerouting of chick hindbrain neural crest

Previous analyses of single neural crest cell trajectories have suggested i mportant roles for interactions between neural crest cells and the environm ent, and amongst neural crest cells. To test the relative contribution of i ntrinsic versus extrinsic information in guiding cells to their appropriate sites, we ablated subpopulations of premigratory chick hindbrain neural cr est and followed the remaining neural crest cells over time using a new in ovo imaging technique. Neural crest cell migratory behaviors are dramatical ly different in ablated compared with unoperated embryos. Deviations from n ormal migration appear either shortly after cells emerge from the neural tu be or en route to the branchial arches, areas where cell-cell interactions typically occur between neural crest cells in normal embryos. Unlike the pe rsistent, directed trajectories in normal embryos, neural crest cells frequ ently change direction and move somewhat chaotically after ablation, In add ition, the migration of neural crest cells in collective chains, commonly o bserved in normal embryos, was severely disrupted. Hindbrain neural crest c ells have the capacity to reroute their migratory pathways and thus compens ate for missing neural crest cells after ablation of neighboring population s. Because the alterations in neural crest cell migration are most dramatic in regions that would normally foster cell-cell interactions, the trajecto ries reported here argue that cell-cell interactions have a key role in the shaping of the neural crest migration.