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17 Extracellular Matrix

James M. Kramer


All metazoans produce extracellular matrices (ECMs) composed of complex mixtures of glycoproteins and carbohydrates. The structures and compositions of these matrices differ in different tissues, in regions of the same tissue, and at different times in development. ECMs can have many functions such as strengthening tissues under physical stress, acting as barriers that inhibit cell migration or substrates upon which cells migrate, serving as molecular filters, and providing signals that alter cell differentiation. Two types of ECMs have been identified in Caenorhabditis elegans: the cuticle and basement membranes. The cuticle covers the outside of the animal and lines the stomodeum and rectum. Basement membranes cover most internal organs, separating them from the pseudo-coelomic cavity. Although most metazoans contain interstitial matrix that lies between the cells within tissues, no interstitial matrix is seen in C. elegans or apparently in other nematodes.

C. elegans is an excellent system for genetic analysis of ECM structure and function. Many of the same molecules found in mammalian ECM (collagens, proteoglycans, laminins) have been identified in C. elegans, and for the most part, their sequences have been highly conserved. The simple, well-defined anatomy and powerful genetics of C. elegans allow for detailed analyses of ECM function that complement the intensive biochemical analyses performed in mammals. This chapter reviews the composition and genetic and molecular studies of the cuticle and basement membranes of C. elegans. Other reviews also describe molecular and genetic analyses of C. elegans (Edgar et al. 1982; Cox 1992; Johnstone 1994; Kramer...

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