Epithelial cell movements and interactions in limb, neural crest and vasculature

Formation of the thickened epical ectodermal ridge of developing vertebrate limbs appears to be a complex process. Direct connections to molecular con trols of cell migratory machinery have been shown for first time in neural crest migration. New unsuspected roles are emerging for ephrin ligand/Eph r eceptor signalling in vascular morphogenesis.