CHARACTERIZATION AND LOCALIZATION OF LARGE SULFATED GLYCOPROTEINS IN THE EXTRACELLULAR-MATRIX OF THE DEVELOPING ASTEROID PISASTER-OCHRACEUS

In this study techniques commonly used to extract and purify proteogly cans of vertebrates were applied to the embryo of the asteroid Pisaste r ochraceus at the early bipinnaria larva stage, a stage in which exte nsive cell migration is occurring within the extracellular matrix of t he blastocoel. Several large sulfated glycoproteins were isolated and shown to consist of protein cores covalently bound to sulfated polysac charide chains. The polysaccharide chains consisted primarily of neutr al sugars and were not susceptible to glycosaminoglycan-degrading enzy mes, suggesting that these were not glycosaminoglycans. The sulfated g lycoproteins could be fractionated by electrophoresis on sodium dodecy l sulfate - agarose -acrylamide composite gels. Two types of monoclona l antibodies prepared against isolated extracellular matrix of these e mbryos reacted with two subsets of bands on Western blots of the compo site gels. Staining of sections of the embryos with the antibodies sho wed that the epitopes that they recognized were located throughout the extracellular matrices of the embryos. That these high molecular weig ht glycoproteins were located within the extracellular matrix of the e mbryos suggests that they may be involved in the control of morphogene sis and cellular movement.