McCauley, D.W.*; Bronner-Fraser, M.: Cranial neural crest cell migration in the lamprey Petromyzon marinus

The neural crest is a vertebrate-specific population of cells that gives rise to much of the peripheral nervous system, pigment cells, and many craniofacial derivatives including facial bones, cartilage, teeth, and cranial ganglia. We have begun to investigate the origin of these cells in the lamprey, the most basal extant vertebrate. Here we describe the migration of cranial neural crest cells into the pharyngeal arches by using a cell lineage tracer, DiI. Small regions of cells along the dorsal midline were labeled with DiI at the time of neural crest cell migration. Embryos were allowed to develop and were then fixed at various intervals following migration. We show that cranial neural crest migratory pathways do not differ appreciably from those previously demonstrated in more derived vertebrates, such as the frog, even though the lamprey lacks such neural crest derivatives as jaws and true teeth. Interestingly, although cells were labeled posterior to the hindbrain, no migratory crest cells were seen in this region. This observation may relate to the lack of sympathetic chain ganglia, another neural crest derivative not found in the lamprey. These studies will be used to correlate the expression of known neural crest markers with migratory pathways to begin to understand the level of conservation of neural crest developmental mechanisms between basal and derived vertebrates.