Kinesin-1 functions in vertebrate development and disease
Campbell, Philip D.
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Cells are often organized with distinct subcellular compartments that fulfill specific cellular functions. Integral to this organization are the molecular motors that transport or tether components to their destinations. The Kinesin superfamily is composed of 45 Kinesin motor proteins (Kifs) in mammals; therefore, there is extensive potential for redundancy and compensation between Kifs. To fully understand their unique and redundant functions Kifs must be considered singly and in combination, preferably in the context of an intact organism.;Kinesin-1, a dimer of Kif5 proteins, has been implicated in numerous biological processes. Mammals have three kif5 genes, kif5A, kif5B, and kif5C, which may allow for diversification of Kinesin-1-mediated functions. Due to their similar protein structures and functions in vitro, Kif5s are thought to act largely redundantly. However, kif5 mouse knockouts have distinct phenotypes and humans with kif5A and kif5C mutations have distinct diseases.;To study how the expanded vertebrate kif5 family contributes to development and disease, I utilized molecular genetic approaches in zebrafish. By analyzing kif5A and kif5B zebrafish mutants I have identified cell-type specific roles for individual kif5s. Specifically, loss of kif5A causes a sensorimotor syndrome in zebrafish reminiscent of loss of kif5A in humans. I have shown that kif5A is required to transport mitochondria to the periphery of sensory axons and for axonal maintenance. Furthermore, overexpression of Kif5A but not other Kif5s nor Kif1B prevents sensory neuropathy. My analysis of kif5B revealed its requirement to properly pattern the embryonic axes and to specify the germline stem cells. l have shown that perturbed patterning results from cytoskeletal and cargo localization defects in the early zygote and that germline stem cell specification defects likely result from loss of Kif5B mediated transport of the germ plasm aggregating factor Bucky ball. Finally, to enable live imaging of RNA transport dynamics, which are likely defective in kinesin mutants, I have also successfully adapted to zebrafish the MS2-MCP RNA-labeling technique.;This thesis work has revealed requirements for specific Kif5s in specific cell types and processes, has answered significant questions in the fields of early patterning and neurodevelopment, and has generated important tools for future studies.