Abstract
Neural crest cells migrate extensively during embryonic development and differentiate into a wide variety of cell types. Our working hypothesis is that during migration, embryonic cells secrete proteases which modify local microenvironments, thereby facilitating directed cellular movements. In this communication, we report studies on the migration of cephalic neural crest cells in the avian embryo. We demonstrate that these cells produce high levels of the serine protease, plasminogen activator (PA), at the time of their initial migration from the neural tube and during their migration to and colonization of the developing head and neck.