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“Expansion microscopy-based spatial biology technologies for biomedical research”
Dr. Rui Gao, Assistant Professor, Biological Sciences & Chemistry University of Illinois Chicago
Understanding the molecular profile and function of a complex biological system requires investigation of its molecular composition and dynamics at high spatiotemporal resolution. Conventional imaging methods, however, suffer from trade-offs between factors such as spatial resolution, molecular specificity, and imaging speed. In this seminar, I focus on ongoing efforts that overcome these limitations to allow nanoscale imaging of biological and clinical specimens with molecular contrast.
First, I introduce expansion microscopy, an emerging biochemical method that enables nanoscale imaging of a broad range of biomolecules, including proteins, RNAs, and lipids, in intact specimens. We recently showed that a type of step-growth-polymerization-based hydrogel maintains nanoscopic structural homogeneity, which ensures that the relative positions of anchored biomolecules are preserved with sub-10 nm accuracy before and after expansion. Using this hydrogel to expand individual virions, we determined the locations of glycoproteins (or protein clusters) on the viral envelopes with a confocal fluorescence microscope. Next, by combining tissue expansion and ultrafast volume fluorescence microscopy, we established a scalable imaging platform to capture the nanoscopic anatomical and molecular profile of millimeter-scale specimens. Using this approach, we characterized the morphological features of more than 1500 dendritic spines, determined the variation of pre- and postsynaptic distances, and studied the radial and longitudinal profiles of axonal myelinations across the entire stretch of a mouse cortical column. In addition, we mapped all the dopaminergic neuron projections and close to 40 million presynaptic sites across the fly brain. Lastly, I discuss the significance and application of these methods for emerging spatial omics studies.
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