Mapping and Characterizing the Neuropil-Associated Glia in Drosophila Larvae

Abstract

In Drosophila central nervous system, neurons and glia collaborate on tasks that are essential for the survival and development of neural organization, such as energy metabolism and neurogenesis. Astrocyte-like glial cells closely associate with the synaptic region neuropil in the ventral nerve cord (VNC). To obtain a better understanding of their potential contribution to neuronal circuit function, the spatial relationship between neurons and glial cells must be characterized. In the first phase of this study, I determined the number of glial cells and their positions in two specific VNC segments (3rd thoracic and 1st abdominal) of 3rd instar Drosophila larvae by employing a genetically encoded fluorescent protein, GFP, targeted specifically to the glial cell bodies and labeling a Fasciclin II positive axons as reference points. The confocal image reconstructions revealed that each segment typically had ten glial cells and only about half of them were consistently observed. In the second phase, I used Flybow technique to induce the expression of different fluorescent proteins in glial cells and observed their branching pattern. These glial cells extended their branches in stereotyped positions in the neuropil suggesting that each glial cell occupies its own domain, consistent with findings for astrocytes in vertebrate cortex.