Proteoglycans in the nervous system - the quest for functional roles in vivo

Large numbers of different proteoglycans are expressed in tightly regulated spatio-temporal patterns by both the nerve cells (neurons) and the support ing glial cells of the nervous system. Several of these proteoglycans have been shown by studies in vitro to affect the migration of neural precursor cells, the elongation and pathfinding of neurites and the formation and sta bilization of synapses. Such processes are important for the accurate wirin g of the nervous system, and so it has been postulated that proteoglycans p lay an essential role during neural development. However, with few exceptio ns, the phenotypes of null mutations in mice and some human genetic disease s have provided little support for this view. Here we will review recent da ta from both in vitro and in vivo studies analyzing the function of proteog lycans in the nervous system in order to provide possible explanations for their apparent lack of function. (C) 2001 Elsevier Science B.V./Internation al Society of Matrix Biology. All rights reserved.