UBC Theses and Dissertations
Laminin and Dystroglycan function in Drosophila wrapping glia ensheathment during development Clayworth, Katherine
Peripheral nervous system (PNS) health is largely dependent on proper glial cell functioning during development. Myelinating and non-myelinating Schwann cells are glial cells in the PNS that ensheathe and protect axons. Communication between Schwann cells and the extracellular matrix (ECM) is essential for PNS development. The ECM protein laminin, and its receptor Dystroglycan [Dg; part of the Dystrophin-glycoprotein complex (DGC)], are important for myelinating Schwann cell development, however little is known about the mechanisms underlying the role of laminins and Dg/DGC in non-myelinating Schwann cell development. We use developing Drosophila wrapping glia (WG), which ensheathe axons similarly to non-myelinating Schwann cells, as a model to study the role of laminin/Dg in non-myelinating Schwann cell development. We found strong expression of LanA (one of two laminin alpha subunits in Drosophila), around WG. Wing blister, the other laminin alpha subunit, is not strongly expressed in the peripheral nerve, indicating that the LamininA isoform is the primary laminin isoform expressed here. We found that WG express LanA, and knockdown of LanA in WG caused perinuclear membrane accumulations and a reduction in WG-axon contact. We found that LanA is deposited in a polarized manner—LanA is preferentially localized between WG and axons (rather than between WG and its adjacent glial layer, subperineurial glia), and preferentially around motor axons versus sensory axons. We also found the laminin receptor Dg is expressed on WG membranes, and we identified differential expression of Dg isoforms in different layers of the peripheral nerve. Knockdown of Dg in WG causes a WG morphology defect, reduction in WG-axon contact, and reduction in laminin deposition in the WG-axon area. We also found that knockdown of Dystrophin, the intracellular binding partner to Dg, phenocopies the Dg-mediated WG morphology defect, suggesting that these proteins likely function together in mediating WG morphology during development. Overall, we characterized a novel localization pattern and function of laminin and Dg in Drosophila WG during development. Due to the highly conserved nature of laminins and DGC proteins, our results have implications for non-myelinating Schwann cell development—thus improving our understanding of the factors underlying PNS development in all animals.
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