DISTRIBUTION, CLASSIFICATION, AND DEVELOPMENT OF DROSOPHILA GLIAL-CELLS IN THE LATE EMBRYONIC AND EARLY LARVAL VENTRAL NERVE CORD

To facilitate the investigation of glial development in Drosophila, we present a detailed description of the Drosophila glial cells in the v entral nerve cord. A GAL4 enhancer-trap screen for glial-specific expr ession was performed. Using UAS-lacZ and UAS-kinesin-lacZ as reporter constructs, we describe the distribution and morphology of the identif ied glial cells in the fully differentiated ventral nerve cord of firs t-instar larvae just after hatching. The three-dimensional structure o f the glial network was reconstructed using a computer. Using the stra ins with consistent GAL4 expression during late embryogenesis, we trac ed back the development of the identified cells to provide a glial map at embryonic stage 16. We identify typically 60 (54-64) glial cells p er abdominal neuromere both in embryos and early larvae. They are divi ded into six subtypes under three categories: surface-associated glia (16-18 subperineurial glial cells and 6-8 channel glial cells), cortex -associated glia (6-8 cell body glial cells), and neuropile-associated glia (8-10 nerve root glial cells, 14-16 interface glial cells, and 3 -4 midline glial cells). The proposed glial classification system is d iscussed in comparison with previous insect glial classifications.