Tenascin-C, tenascin-R and tenascin-X: a family of talented proteins in search of functions.

"Mice develop normally without tenascin", was a shock to biologists studying the extracellular matrix. Could tenascin be a useless protein? This seems most improbable, as it is conserved in every vertebrate species. Moreover, two new proteins have been discovered in the last year that are closely related to the original tenascin, providing evidence for a tenascin family. Speculations on functions are ripe for re-evaluation.