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UBC Theses and Dissertations

A systematic analysis of the role of the cytoskeleton in Drosophila melanogaster muscle maintenance Perkins, Alexander David


Animal muscles must maintain their function while bearing substantial mechanical loads and undergoing numerous contraction/extension cycles. How muscles withstand persistent mechanical strain is presently not well understood. The basic unit of muscle is the sarcomere, which is primarily composed of cytoskeletal proteins. I hypothesized that cytoskeletal proteins undergo renewal via protein turnover and that this is required to maintain muscle function. Using the adult flight muscles of the fruit fly, Drosophila melanogaster, I confirmed that the sarcomeric cytoskeleton undergoes turnover throughout the life of the organism. To uncover which cytoskeletal components are specifically required to maintain adult muscle function I performed an RNAi-meditated knockdown screen in adult D. melanogaster targeting the entire fly “cytoskeletome”, the set of known cytoskeletal and cytoskeletal-associated proteins. Systematic gene knockdown was restricted to adult flies and muscle function was analyzed with behavioural assays. This approach identified 47 genes required for maintaining muscle function, 40 of which had no previously known role in this process. Detailed analysis of the role of candidate genes in adult muscles using confocal and electron microscopy showed that while muscle architecture was largely maintained after gene knockdown, maintenance of sarcomere length was disrupted. Specifically, I found that the ongoing synthesis and turnover of the key structural sarcomere component Projectin (bent) was required to maintain M-line integrity. Together, these results provide direct in vivo evidence of muscle protein turnover and identify possible roles for this process by uncovering specific functional defects associated with reduced expression of a subset of cytoskeletal proteins in the adult animal.

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