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 su lfated 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), 2 2%; (3) UA-1 --> 4-GlcNAc(6SO(4)), 14% and (4) UA-1 --> 4-GlcN(SO4), 11%. T wo 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 incor poration into the eggs reveal that the sulfated glycans are present exclusi vely in the test cells. Possibly these sulfated polysaccharides are involve d 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) 1 999 Elsevier Science B.V. All rights reserved.