PgmNr D1256: Regulation of Neuron-Glia Interactions in the Developing Eye.

Authors:
Victoria Hans; Asma Patel; Jennifer Jemc


Institutes
Loyola University Chicago, Chicago, IL.


Keyword: glia

Abstract:

Glial cells in vertebrates have numerous functions, including myelination of neuronal axons. While Drosophila don’t have myelination to increase the efficiency of action potential transmission, a subpopulation of glia wrap around neurons to support neuron function. Previous studies have shown that when raw expression is reduced in glia, the result is lethality during pupal stages, leading us to ask what the role of raw is in glia during development. The developing eye of Drosophila provides an excellent system for studying the role of raw in glia due to its well-characterized glial subtypes and well-described development. Perineurial glia start in the brain and optic stalk, then migrate into the developing eye imaginal disc during the third larval instar, where they make contact with photoreceptor cells. Following contact with neurons, perineurial glia differentiate into wrapping glia and ensheath photoreceptor axons. Axons then extend along glia to the optic lobe of the brain. Our studies using immunohistochemistry have revealed a reduction in the number of glia in the third instar eye imaginal disc when raw levels are reduced in glial cells using the Gal4/UAS system to produce raw RNAi. While we observe a reduction in the number of glia, it is unclear if the reduction of glia is due to cell death, reduced proliferation, or defects in specification. Preliminary studies in the embryo suggest that glia are properly specified early in development in raw mutants, making it unlikely that glia specification is the origin of the raw mutant phenotype. To determine if the reduction arises from an increase in cell death we have performed immunostaining for activated Caspase, as well as acridine orange and do not observe an increase in cell death. Currently, we are using an antibody for phospho-histone H3 to determine if glial proliferation is reduced in raw RNAi samples relative to controls. Finally, it is possible that the reduction in glia in the eye disc arises from defects in glial migration. In order to examine this possibility, a live imaging approach is being developed to examine glial migration in cells with reduced raw levels. Images will be taken every 10-15 minutes over the course of a few hours to observe the glial migration process, allowing us to track the path of specific glial cells and to examine the rate at which glia are migrating. Finally, glia are important for proper axon targeting to the optic lobe of the brain. In larvae with reduced raw levels in glia, we observe axon mis-targeting in the brain, suggesting that Raw functions indirectly to regulate axon targeting as well. Thus, we have identified a new regulatory protein that functions in cell autonomously in glia cell non-autonomously in neurons during development.



Flybase Genetic Index:
1. FlyBase gene symbol: raw; FBgn: FBgn0003209