Isolation and characterization of a highly sulfated heparan sulfate from ascidian test cells

Several sulfated polysaccharides have been isolated from the test cells of the ascidian Styela plicata. The preponderant polysaccharide is a highly sulfated heparan sulfate with the following disaccharide composition: (1) UA(2SO(4))-1 --> 4 GlcN(SO4)(6SO(4)), 53%; (2) UA(2SO(4))-1 --> 4-GlcN(SO4), 22%; (3) UA-1 --> 4-GlcNAc(6SO(4)), 14% and (4) UA-1 --> 4-GlcN(SO4), 11%. Two others unidentified sulfated polysaccharides and a glycogen polymer are also present in the ascidian eggs. Histochemistry with the cationic dye 1,9-dimethyl-methylene blue and biochemical analysis of the S-33-sulfate incorporation into the eggs reveal that the sulfated glycans are present exclusively in the test cells. Possibly these sulfated polysaccharides are involved in important functions of these cells. such as to confer an external and hydrophilic layer which protect the eggs and the larvae of ascidians. (C) 1999 Elsevier Science B.V. All rights reserved.