SELECTIVE EARLY INNERVATION OF A SUBSET OF EPIDERMAL-CELLS IN XENOPUSMAY BE MEDIATED BY CHONDROITIN SULFATE PROTEOGLYCANS

The epidermis of early Xenopus embryos is innervated by the Rohon-Bear d (RE) neurons lying within the spinal cord and by extramedullary (EM) neurons lying outside of the cord. We have examined the innervation p atterns of the three epidermal cell types using wholemount preparation s of skin double-labelled with the HNK-1 antibody as a marker for neur ons and with antibodies to chondroitin sulfate proteoglycan (CSPG). Ce lls of one of the three epidermal cell types, here termed conical cell s, are innervated well before the other two. In wholemounts of embryon ic skin incubated with antibodies to chondroitin-6-sulfate (C6S), all epidermal cells except conical cells show CSPG immunoreactivity in the ir basal lamina. Double-labelling of skin preparations with HNK-1 and anti-C6S confirmed that these conical cells which lack C6S immunoreact ivity are the first to be innervated by RE axons. It is proposed that C6S-bearing proteoglycan initially inhibits innervation of cells whose basal lamina contain the proteoglycan, thus favoring innervation of t he conical cells which lack it. (C) 1997 Elsevier Science B.V.