“…Several immunohistochemical and ultrastructural studies in both tetrapods (e.g., Pavola et al, 1980;Hay, 1984;Camón et al, 1990;Gotz et al, 1995;Ghanem, 1996) and cyclostomes (Kimura and Kamimura, 1982;Welsch et al, 1991) have demonstrated the presence of different extracellular matrix (ECM) proteins in intercellular spaces and under the basal lamina of the notochordal sheath, such as type I and II collagen fibers, sulphated glycosaminoglycans, glycoproteins (fibronectin, laminin, and tenascin), and proteoglycans (e.g., decorin). However, the complete molecular nature of the notochord sheath-associated ECM proteins, and their possible role in the modulating signaling to or differentiation of neighbouring embryonic tissues (e.g., Ashkenas et al, 1996), are still poorly understood.…”