TENASCINS, A GROWING FAMILY OF EXTRACELLULAR-MATRIX PROTEINS

The tenascins are a family of large multimeric extracellular matrix pr oteins consisting of repeated structural modules including heptad repe ats, epidermal growth factor (EGF)-like repeats, fibronectin type III repeats, and a globular domain shared with the fibrinogens. The tenasc ins are believed to be involved in the morphogenesis of many organs an d tissues. To date three members of the tenascin family have been desc ribed, tenascin-C, tenascin-R, and tenascin-X. Tenascin-R seems to be specific for the central and peripheral nervous system, tenascin-X is most prominent in skeletal and heart muscle, while tenascin-C is prese nt in a large number of developing tissues including the nervous syste m, but is absent in skeletal and heart muscles. Tenascin-C was the ori ginal tenascin discovered, partly because of its overexpression in tum ors. Inferring from cell biological studies, it has been proposed that tenascin-C is an adhesion-modulating protein.