Genetic dissection of peripheral glia and glial sheath development

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The long-term goal of my research program is to understand how glia ensheath and protect the peripheral nerve. We study the mechanisms that underlie glia development in Drosophila melanogaster, where each peripheral nerve is insulated by layers of glia and insulation is essential for nervous system function. Little is known about the mechanisms that trigger glia to migrate along and wrap axons or surround and support the nerve. The formation of the glial wrap involves adhesion and communication between glia-glia, glia-axon and glia-extracellular matrix (ECM) paired with extensive rearrangements of the cytoskeleton. In Drosophila three distinct glial layers contribute to the mature peripheral nerve and the glial sheath must be maintained and expand to match animal growth. Loss of glia-glia adhesion disrupts the glial sheath leading to paralysis and lethality due to loss of the blood-brain barrier (BBB), yet how the sheath forms and is maintained is not well understood. Loss of the glia-ECM interaction leads to disruption of the structure of the CNS and peripheral nerve integrity. The aim of my research is to identify the mechanisms underlying glial sheath formation and test the functional consequences that disruption of these highly conserved processes have on nervous system function. Our NSERC funded research identified protein complexes critical to establish the glial sheath. We found that integrins are key to glia-glia and glia-ECM communication in the peripheral nervous system and maintain the glial sheath and the BBB. We found Basigin (Bsg) regulates integrin-mediated glial adhesion to the ECM. We determined that Cadherins ensure the formation of the glial wrap and BBB. Of interest, Cadherins and Integrins function together in this process and understanding how these complexes control glial ensheathment is the next step in our research program. The two short term goals of the current grant are to determine the mechanisms that: Aim 1) Underly the convergence of integrin and cadherin function in sheath and BBB formation. Aim 2) Link integrins and Basigin to modulate glia-ECM interactions and ensure the structural integrity of the peripheral nerve. My laboratory has extensive experience studying peripheral glia development and sheath formation. We have generated a suite of genetic tools that allow us to manipulate the genes expressed in each of the three peripheral glia layers and then assess the results on nervous system function and morphology. We utilize a multi-faceted approach that incorporates genetics (including RNAi, CRISPR genome editing), cell biology (including fluorophore-tagged endogenous proteins, FRET based tension sensors), biochemistry (including proximity ligation assays), optogenetics to regulate axonal activity, super-resolution imaging and behaviourial studies. Thus we use the Drosophila model to characterize the fundamental mechanisms that underlie glial cell development and sheath formation in all animals.