REGULATION OF THE CHICK CUTANEOUS INNERVATION PATTERN IN RETINOIC ACID-INDUCED ECTOPIC FEATHERS AND IN THE NAKED NECK MUTANT

In chick skin, nerve fibers develop in a typical network formed by arc ades around the base of feathers. In this study, we tried to dissociat e the morphogenesis of nerve arcades and feathers, and to clarify the implication of several matricial molecules in these two developmental events. For this purpose, cutaneous nerve pattern and distribution of fibronectin, tenascin, and three epitopes of chondroitin sulfate prote oglycans (CSPGs) have been immunohistologically studied in the skin of the specific apteria of naked neck chick mutants, which lack feathers in the neck area, and in the tarso-metatarsal zone of retinoic acid-t reated embryos where ectopic feathers grow. The presence of feathers w as always associated with nerve arcades; no arcades were present in fe atherless areas. Specific immunofluorescence for tenascin and two epit opes of CSPGs revealed different distributions in the naked-neck neo-a pteria as compared to control apteria. Moreover, the only difference i n matricial composition in ectopic feathers concerned a CSPG isoform, bringing additional evidence that extracellular matrix molecules, and especially some (but not all) CSPGs, are involved both directly and in directly in the cutaneous nerve pattern development.