Involvement of a chondroitin sulfate proteoglycan in the avoidance of chick epidermis by dorsal root ganglia fibers: a study using beta-D-xyloside

In 7-day chick embryo dorsal root ganglia and epidermis cocultures, nerve fibers avoid the epidermis. Previous studies have indicated that glycoproteic factors, secreted by epidermis, could be involved in this phenomenon. Treatment of epidermis by beta-D-xyloside, a specific proteoglycan synthesis inhibitor, abolishes the avoidance reaction. The same result is obtained when anti-chondroitin sulfate antibodies are added to the culture medium. Using HPLC and 35SO4 labeling combined with chondroitinase and hyaluronidase treatment, it has been demonstrated that chondroitin sulfate is present in the epidermal conditioned medium. This suggests that a chondroitin sulfate proteoglycan secreted by the epidermis is implicated in the neurite avoidance reaction and that epidermis could therefore control its own "noninnervation". In vivo, inhibitory influences by local extracellular components may control the guidance of growth cones during nerve pattern formation.