Biology

Dr. Shalin Mehta
University of Chicago and Marine Biological Laboratory

Our recent work has led to fluorescence-based computational microscopy assays that reveal nanoscale architecture of molecules within the context of microscale assemblies. We exploit intrinsic polarization of fluorescence to measure sub-resolution orientation and alignment of molecules. We have developed a microscope, dubbed instantaneous fluorescence polarization microscope (instantaneous fluorescence PolScope), to acquire four polarization-resolved measurements with single molecule sensitivity. We retrieve orientation, concentration, and kinetics of cytoskeletal networks by combining instantaneous fluorescence PolScope and computational analysis of the spatiotemporal distribution of fluorophores. This computational microscopy approach revealed nanoscale orientation of actin filaments relative to the retrograde flow of the network at the leading edge of cells migrating on 2D surfaces. Analysis of actin filament orientation at the leading edge has been possible only in fixed cells with electron microscopy. Further, in a multi-institutional collaboration, synergistic use of fluorescence polarization microscopy and computational analysis revealed that integrin transmembrane receptors are ‘actively aligned’ by their engagement with retrograde flow and extracellular ligand. The active alignment of integrin receptors may be a general mechanism used by cells to sense directional cues within extracellular matrix and is uniquely accessible with fluorescence polarization microscopy in live cells.

Building upon these advances, the future studies will reveal the molecular architectural basis of the directional forces generated by single cells and a collective of cells within 3D (patho)physiological environments.