KERATAN SULFATE IS PRESENT IN DEVELOPING CHICK SKIN IN-VIVO WHERE IT COULD CONSTITUTE A BARRIER TO ADVANCING NEURITES AS OBSERVED IN-VITRO

Proteoglycans play an important role in axonal guidance, The glycosami noglycan chondroitin sulphate is known to be inhibitory. Keratan sulph ate is structurally similar and may play a similar role. The lectin pe anut agglutinin potentially labels chondroitin or keratan sulphate ric h areas. In order to elucidate the mechanisms by which the regular ner ve pattern develops in chick skin, keratan sulphate epitopes and peanu t agglutinin binding sites were localized in chick embryos and compare d to previous studies of chondroitin sulphate. The markers all display specific, developmentally regulated staining patterns, thus reflectin g their individuality. Their maximal expression coincides with the for mation of feathers and their nerve pattern in both time and space. Fur thermore, culture experiments using dorsal root ganglia demonstrate th e avoidance of keratan sulphate by the growing sensory neurites, altho ugh outgrowth and elongation occur if they grow directly on the kerata n sulphate substrate. Thus, keratan sulphate proteoglycans in developi ng chick skin are potentially involved in guidance of sensory neurites or maintenance of the new nerve pattern, but are clearly different to the chondroitin sulphate proteoglycans which have a complementary dis tribution. Furthermore, peanut agglutinin binding sites are independen t of both proteoglycans. (C) 1997 Wiley-Liss, Inc.