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UBC Theses and Dissertations

An unconventional role for the septate junctions and Gliotactin in cell division Charish, Kristi


The focus of this thesis is to investigate the integration of cell division with the septate junction domain in the Drosophila imaginal wing disc epithelium. Columnar epithelia of the imaginal wing disc exhibit complex architecture due to an elaborate series of junctions that are found throughout the membrane. During cell division, these junctions are maintained while new junctions are established; however, their role and influence during mitosis is unclear. This thesis shows that the septate junctions are essential for cytokinesis and Gliotactin at the tricellular junctions is necessary to localize cell division to the septate junction domain, and illustrates a unique role for Gliotactin and the septate junctions outside their classic role of maintaining a permeability barrier. The septate junctions are basolaterally localized transmembrane junctions required in epithelial cells to form a permeability barrier. Although the septate junctions are formed by a large protein complex, this thesis only investigates the three core SJ proteins, NeurexinIV (NrxIV), Coracle (Cor), and Neuroglian (Nrg). Gliotactin (Gli), a Drosophila Neuroligin homologue, is a septate junction associated protein concentrated at the tricellular junction (TCJ), which is necessary to maintain the septate junction permeability barrier. Loss of any of the septate junction proteins, or Gliotactin, leads to structural disruption of the septate junctions and loss of the permeability barrier in a wide range of epithelial derived tissues. Chapter two examines the process of cell division in epithelial cells of the wing imaginal disc with respect to the septate junctions and tricellular junction. Chapter three looks at the role of Gliotactin in maintaining the plane of cell division within the septate junction domain, and chapter four shows that the septate junctions are necessary for ingression furrow stability and the association of the contractile ring with the membrane during late cytokinesis. This work demonstrates a novel role for the septate and tricellular junctions during mitosis in Drosophila, which has implications for the role of tight junctions in vertebrate cells.

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