Chondroitin sulphate mediated fusion of brain: neural folds in rat embryons

Abstract

Previous studies have demonstrated that during neural fold fusion in different species, an apical extracellular material rich in glycoconjugates is involved. However, the composi- tion and the biological role of this material remain undeter- mined. In this paper, we show that this extracellular matrix in rat increases notably prior to contact between the neural folds, suggesting the dynamic behaviour of the secretory process. Immunostaining has allowed us to demonstrate that this extracellular matrix contains chondroitin sulphate proteoglycan (CSPG), with a spatio-temporal distribution pattern, suggesting a direct relationship with the process of adhesion. The degree of CSPG involvement in cephalic neu- ral fold fusion in rat embryos was determined by treatment with specific glycosidases. In vitro rat embryo culture and microinjection techniques were employed to carry out se- lective digestion, with chondroitinase AC, of the CSPG on the apical surface of the neural folds; this was done immediately prior to the bonding of the cephalic neural folds. In all the treated embryos, cephalic defects of neural fold fusion could

tant role in the fusion of the cephalic neural folds in rat em- bryos, which implies that this proteoglycan could be in- volved in cellular recognition and adhesion.

Abbreviations used in this paper

CSPG chondroitin sulphate proteoglycan HSPG heparan sulphate proteoglycan PBS phosphate-buffered saline SEM scanning electron microscopy

be detected. These results show that CSPG plays an impor-