COLLABORATIVE RESEARCH: Role of Glia during Postembryonic Formation of the CNS

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Lay Summary - Collaborative Research: Fahrbach and Mesce Insect metamorphosis is accompanied by extensive reorganization of the central nervous system. These changes are regulated by steroid hormones, and during metamorphosis insect neurons and glia express nuclear steroid hormone receptors. A notable feature of metamorphosis in the nervous system of moths and butterflies is the formation of compound ganglia from individual segmental ganglia. In the moth Manduca sexta, a large species easily reared in the laboratory, compound ganglia form shortly after the caterpillar pupates. This collaborative project will test a model of compound ganglion formation in which two classes of glial cells are the primary steroid targets. In this model, the giant glial cells of the interganglionic connectives move clusters of neurons by changes in their cytoarchitecture while the perineurial glial cells that wrap the central nervous system alter their adhesive properties to permit the neurons to move freely. Experiments to be conducted at the University of Minnesota in Dr. Mesce's laboratory will describe the motility of giant glial cells during the formation of compound ganglia and will study how damage to the giant glial cells affects ganglionic migration and fusion. These experiments are facilitated as a result of the recent discovery that a form of fasciclin II, a protein expressed on the surface of insect cells, can be used as a marker for the giant glial cells. Experiments to be conducted in Dr. Fahrbach's laboratory at the University of Illinois at Urbana-Champaign will determine the timing of perineurial glial cell proliferation during metamorphosis and study the effects of ablation of this cell population on ganglionic migration and fusion. In addition, antibodies targeted to specific isoforms of the insect steroid hormone receptor (the ecdysone receptor, EcR) will be used to determine which form of the receptor is expressed by glial cells. This is envisioned as a first step toward identifying steroid-regulated genes involved in regulation of the glial cytoskeleton and glial cell adhesion molecules.Previous studies of metamorphosis of the insect nervous system have focused exclusively on neurons. This project will provide new information about the developmental modulation of glial cell cytoarchitecture and glial cell adhesivity during the postembryonic life of insects. The results are likely to generalize to all arthropods and, because the regulation of cell "stickiness" and cell shape are fundamental attributes of all multicellular organisms, to other animals as well.