Extracellular Matrix 2 : Role of extracdllular matrix rnoiecui # { 243 } and their receptors in the nervous system

Extracellular matrix molecules help regulate many aspects of neural development, including survival, migration, axon growth, and synapse formation by neurons. These same molecules have been shown to modulate regeneration of neurons after injuries. They also regulate the development and differentiation of other neural cells, such as astroglia and Schwann cells. Significant progress has been made recently in characterizing both ECM constituents and their receptors in the nervous system. Extracellular matrix molecules promote cell adhesion, activate intracellular signaling pathways, and modulate the activities of several growth factors and proteins. Our current understanding of the extracellular matrix, its receptors, and its functions in the nervous system are discussed.-Venstrom, K. A., Reichardt, L. F. Role of extracellular matrix molecules and their receptors in the nervous system. FASEBJ. 7: 996-1003; 1993. Key Wonis. exLmcellularmalrzx ne7voUs.9/stem ipJeins . laminin. proteoglycans ThE EXTRACELLULAR MATRIX (ECM)2 is a complex set of collagens, noncollagenous glycoproteins, and proteoglycans that has a unique composition in each organ of the body (Fig. 1). Expression of ECM molecules is tightly regulated; some are transiently expressed at particular times in development, whereas others are continually expressed into adulthood. In the nervous system, the ECM helps regulate cell migration, survival, differentiation, and axonal pathflnding (for other reviews, see ref 1). The ECM has also been shown recently to bind several growth factors present in the nervous system. Interactions with the ECM regulate their diffusion, stabilities, and activities. Evidence for the importance of the ECM in the developing nervous system has largely been accumulated by examination of effects of individual ECM proteins as assayed in culture systems in vitro and expression patterns of these same proteins in vivo. Function blocking antibodies have been particularly useful in culture to determine the importance of individual ECM molecules and to identify their receptors (Table 1). In some cases, antibodies have been injected into embryos and used to provide more direct evidence for the functions of these ECM proteins in vivo. NEURONAL RECEPTORS FOR ECM