SEGMENTAL MIGRATION OF TRUNK NEURAL CREST - TIME-LAPSE ANALYSIS REVEALS A ROLE FOR PNA-BINDING MOLECULES

Trunk neural crest cells migrate through the somites in a striking seg mental fashion, entering the rostral but not caudal sclerotome, via cu es intrinsic to the somites. Attempts to define the molecular bases of these cues have been hampered by the lack of an accessible assay syst em. To examine trunk neural crest migration over time and to perturb c andidate guiding molecules, we have developed a novel explant preparat ion. Here, we demonstrate that trunk regions of the chicken embryo, pl aced in explant culture, continue to develop apparently normally for 2 days. Neural crest cells, recognized by prelabeling with DiI or by po ststaining with the HNK-1 antibody, migrate in the somites of the expl ants in their typical segmental pattern. Furthermore, this paradigm al lows us to follow trunk neural crest migration in situ for the first t ime using low-light-level videomicroscopy. The trajectories of individ ual neural crest cells were often complex, with cells migrating in an episodic mode encompassing forward, backward and lateral movements. Fr equently, neural crest cells migrated in close-knit groups of 2-4 cell s, moving at mean rates of migration of 10-14 mu m/hour. Treatment of the explants with the lectin peanut agglutinin (PNA) both slowed the r ate and altered the pattern of neural crest migration. Neural crest ce lls entered both the rostral and caudal halves of the sclerotome with mean rates of migration ranging from 6 to 13 mu m/hour. These results suggest that peanut agglutinin-binding molecules are required for the segmental patterning of trunk neural crest migration. Because this app roach permits neural crest migration to be both observed and perturbed , it offers the promise of more direct assays of the factors that infl uence neural crest development.