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Browsing by Subject "Drosophila oogenesis"

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  • Aung, July (2021)
    Epithelial cells line the surfaces of organs and tissues in a continuous and tightly packed manner, thereby functioning as a protective barrier between the tissue and the external environment known as the epithelium. During development, the epithelium undergoes a series of morphogenetic events which alters the shape and size of epithelial cells, enabling them to perform tissue specific functions in mature tissue. During morphogenesis, cells sense the mechanical forces and establish polarity through cell proliferation and rearrangement according to morphogenetic signalling pathways. This manoeuvre is achieved by the underlying actin cytoskeleton network which enables cells to resist the tension and stresses of morphogenesis via alteration of filament dynamics and network architecture. In vivo, numerous actin-regulatory proteins generate various polymerized forms of straight, branched, or contractile actin-myosin filaments, regulating dynamic actin filament turnover. The robust actin cytoskeleton provides the cell with protrusive and contractile forces that enable cells to migrate, maintain, and change its shape and form during morphogenetic events. Actin filament depolymerization is accomplished by ADF/cofilin (Drosophila homolog twinstar) binding to actin monomers (G-actin) and actin filaments. However, ADF/cofilin alone is not very efficient in promoting disassembly of actin monomers, especially in subcellular regions where ADF/cofilin is highly concentrated. AIP1 (Drosophila homolog flare) then enhances actin depolymerization via preferential binding to ADF/Cofilin rich regions in vitro. The aim of my thesis was to study the localization and roles of AIP1 and cofilin in follicular epithelium during Drosophila oogenesis. My results showed that Actin-Interacting-Protein-1 (AIP1) was expressed throughout oogenesis. AIP1 expression was increased in cell type-specific manner and AIP1 showed spatiotemporal localization in follicular epithelium during oogenesis. Silencing of AIP1 led to accumulation of ectopic F-actin aggregates, localization of which may reflect the cellular sites of dynamic actin reorganization in the follicular epithelium. My results also indicate that AIP1 may be indirectly responsible for maintaining epithelial integrity as its silencing resulted in formation of epithelial gaps throughout follicular epithelium. Also delays in border cell migration were observed. Considering the above, understanding how AIP1 functions in Drosophila morphogenetic events would therefore pave the way for a greater understanding of how this protein works in other organisms. The knowledge gained may also be used to extend the current understanding of the role of actin binding proteins in diseased states.