ROLE OF THE EXTRACELLULAR-MATRIX IN NEURAL CREST CELL-MIGRATION

Development of the neural crest involves a remarkable feat of coordina ted cell migration in which cells detach from the neural tube, take va rying routes of migration through the embryonic tissues and then diffe rentiate at the end of their journey to participate in the formation o f a number of organ systems. In general, neural crest cells appear to migrate without the guidance of long-range physical or chemical cues, but rather they respond to heterogeneity in the extracellular matrix t hat forms their migration substrate. Molecules such as fibronectin and laminin act as permissive substrate components, encouraging neural cr est cell attachment and spreading, whereas chondroitin sulphate proteo glycans are nonpermissive for migration. A balance between permissive and nonpermissive substrate components seems to be necessary to ensure successful migration, as indicated by a number of studies in mouse mu tant systems where nonpermissive molecules are over-expressed, leading to inhibition of neural crest migration. The neural crest expresses c ell surface receptors that permit interaction with the extracellular m atrix and may also modify the matrix by secretion of proteases. Thus t he principles that govern the complex migration of neural crest cells are beginning to emerge.