Glycosaminoglycan Synthesis by Embryonic Inductors: Neural Tube, Notochord, and Lens

Considerable indirect evidence (1-4) and some direct evidence (5-8) indicate that glycosaminoglycans (GAG) promote certain types of morphogenesis and cell differentiat ion. Removal of basement m e m b r a n e by hyaluronidase disrupts salivary gland branching (2) and hyaluronate interferes with chondrocyte aggregat ion (5). On the positive side, chondromucopro te in s t imulates the synthesis of extracellular matr ix by chondrocytes and prechondrocytes (6, 7). Chondro i t in and heparan sulfates and collagen, but not de rmatan or kera tan sulfates or hyaluronate , p romote product ion of pr imary corneal s t roma by corneal epithelium (8, 9), an event which in vivo is said to be induced by