REGULATED EXPRESSION OF KERATAN SULFATE AND PEANUT AGGLUTININ BINDING-SITES DURING ORGANOGENESIS IN THE DEVELOPING CHICK

Keratan sulphate proteoglycans are potentially important during develo pment and are possible binding molecules for the lectin, peanut agglut inin, a marker for areas that are inhibitory for axonal growth in earl y embryos. The present study describes the spatiotemporal distribution s of keratan sulphate epitopes and peanut agglutinin binding sites dur ing organogenesis in the developing chick from E5 to hatching. The wid espread distributions of these molecules did not often overlap but cle arly delimited different carbohydrate compartments demonstrating that peanut agglutinin does not necessarily bind to keratan sulphate proteo glycans. These markers were mostly extracellular but keratan sulphate, in particular, was found within certain specific cells in cartilage, gonad, heart and pancreas, at certain ages. The presence of keratan su lphate in putative germ cells during their migrations and in the gonad s may be of particular importance. Their distributions generally evoke modulation of adhesion allowing cell migrations or morphogenetic move ments related to epitheliomesenchymal interactions, but may also sugge st an involvement in axonal guidance in skin, cartilage,,out and possi bly heart. Furthermore, in the kidney, peanut agglutinin binding sites seem to be related to the functional differentiation of the nephrons.