Dynamics of assembly and reorganization of extracellular matrix proteins.

This chapter will review advances in our understanding of the dynamics of assembly and reorganization of extracellular matrix (ECM) proteins and will highlight the role of fibronectin as a key orchestrator for the assembly of multiple ECM proteins. The dynamic rather than static nature of the ECM will be emphasized by reviewing time-lapse imaging studies in living cell and embryo systems, with a particular focus on fibronectin and members of the fibrillin superfamily. These studies have provided new insights into the assembly and reorganization of ECM fibrillar networks, suggesting that fibril assembly is a hierarchical process, with increasingly larger fibrillar structures formed by the progressive aggregation of smaller units. These studies have also revealed that motile cells appear to be actively involved in the assembly and reorganization of ECM fibrillar networks by shunting fibrillar material from one location to another, adding fibrillar material to the ends of growing fibrils, and exchanging material between fibrils. A common theme emerging from these studies is that cell- and tissue-generated mechanical forces are critical in the assembly and remodeling of the ECM.