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Single-molecule fluorescence and super-resolution imaging of Huntington's disease protein aggregates
- "Single-molecule, super-resolution fluorescence microscopy is a powerful technique for studying biological systems because it reveals details beyond the optical diffraction limit (on the 20-100 nm scale) such as structural and conformational heterogeneity. Further, single-molecule imaging measures distributions of behaviors directly through the interrogation of many individual molecules and reports on the nanoscale environment of molecules. Sub-diffraction imaging adds increased resolution to the advantages of fluorescence imaging over the techniques of atomic force microscopy and electron microscopy for studying biological structures, which include imaging of large fields of view in aqueous environments, specific identification of protein(s) of interest by fluorescent labeling, low perturbation of the system, and the ability to image living systems in near real-time (limited by the time required for super-resolution sequential imaging). This dissertation describes the application of single-molecule and super-resolution fluorescence imaging to studying the huntingtin (Htt) protein aggregates that are a hallmark of Huntington's disease and that have been implicated in the pathogenesis of the disease. The intricate nanostructures formed by fibrillar Htt aggregates in vitro and the sub-diffraction widths of individual fibers mark the amyloids as important targets for high-resolution optical imaging. The characterization of Htt aggregate species is critical for understanding the mechanism of Huntington's disease and identifying potential therapies. Following an introduction to single-molecule, super-resolution imaging and Huntington's disease in Chapter 1, Chapter 2 describes the single-molecule methods, experimental techniques, Htt protein sample preparations, and data analysis performed in this dissertation. Chapter 3 discusses the development of super-resolution imaging of Htt protein aggregates and the validation of the images by atomic force microscopy. Chapter 4 continues the study of Htt by one- and two-color super-resolution with imaging of Htt protein aggregates over time from the initial protein monomers to the large aggregate assemblies of amyloid fibers. In Chapter 5, I detail our progress to-date in studying the earliest stages of Htt aggregation using zero-mode waveguide technology. Chapter 6 concludes the dissertation with a discussion of the results from additional projects comprising the effect of chaperonin proteins on Htt aggregation, extension of super-resolution Htt imaging to three dimensions, and cellular imaging of Htt aggregates. The future directions for these exciting projects are summarized with the expectation that research efforts directed in these areas will contribute to our understanding of Htt aggregation and Huntington's disease."
- "Single-molecule fluorescence and super-resolution imaging of Huntington's disease protein aggregates"