CLOSE LINK BETWEEN CUTANEOUS NERVE PATTERN DEVELOPMENT AND FEATHER MORPHOGENESIS DEMONSTRATED BY EXPERIMENTAL PRODUCTION OF NEO-APTERIA ANDECTOPIC FEATHERS - IMPLICATION OF CHONDROITIN SULFATE PROTEOGLYCANS AND OTHER MATRIX MOLECULES

In chick skin, nerve arcades develop around the base of feathers. In o rder to understand the mechanisms of their formation, we have tried to dissociate arcade formation from feather morphogenesis in various way s. Nerve patterns were analysed (1) in hydrocortisone-treated embryos that are partially devoid of feathers, (2) after retinoic acid treatme nt that produces ectopic feathers, (3) in dorsal root ganglia-skin co- cultures. Whenever tested, immunochemistry revealed that nerve arcades form around chondroitin sulphate proteoglycan-rich areas. Hydrocortis one treatment modifies the distribution of two out of three chondroiti n sulphate proteoglycan epitopes tested, as well as the shapes of the feathers and nerve arcades, but not fibronectin, tenascin or laminin l ocalizations. Chondroitinase digestion in cocultures eliminated the ne rve arcade formation and produced abnormally thin feathers, but nevert heless with a normal spatial distribution. Thus, chondroitin sulphate proteoglycans are probably not involved in the overall arrangement of feathers, but appear to play a fundamental role in both the formation of nerve arcades and the morphogenesis of the feather.