DEVELOPMENT AND ORGANIZATION OF GLIAL-CELLS IN THE PERIPHERAL NERVOUS-SYSTEM OF DROSOPHILA-MELANOGASTER

We have used enhancer trap lines as markers to recognize glial cells i n the wing peripheral nervous system of Drosophila melanogaster. Their characterization has enabled us to define certain features of glial d ifferentiation and organization. In order to ask whether glial cells o riginate within the disc or whether they migrate to the wing nerves fr om the central nervous system, we used two approaches. In cultured win g discs from glial-specific lines, peripheral glial precursors are alr eady present within the imaginal tissue during the third larval stage. Glial cells differentiate on a wing nerve even in mutants in which th at nerve does not connect to the central nervous system. To assess whe ther peripheral glial cells originate from ectoderm or from mesoderm, we cultured discs from which the mesodermally derived adepithelial cel ls had been removed. Our findings indicate that peripheral glial cells originate from ectodermally derived cells. As has already been shown for the embryonic central nervous system, gliogenesis in the periphery is an early event during adult development: glial cells, or their pre cursors, are already present at stages when neurons are still differen tiating. Finally, our results also suggest that peripheral glial cells may not display a stereotyped arrangement.