Expression of zebrafish fkd6 in neural crest-derived glia

The zebrafish fkd6 gene is a marker for premigratory neural crest. In this study, we analyze later expression in putative glia of the peripheral nervo us system. Prior to neural crest migration, fkd6 expression is downregulate d in crest cells. Subsequently, expression appears initially in loose clust ers of cells in positions corresponding to cranial ganglia. Double labellin g with a neuronal marker shows that fkd6-expressing cells are not different iated neurones and generally lie peripheral to neurones in ganglia. Later, expression appears associated with the posterior lateral line and other cra nial nerves. For the posterior lateral line nerve, we show that fkd6-labeli ng extends caudally along this nerve in tight correlation with lateral line primordium migration and axon elongation. Expression in colourless mutant embryos is consistent with these cells being satellite glia and Schwann cel ls. (C) 2000 Elsevier Science Ireland Ltd. All rights reserved.