Monday, February 26, 201812:00 – 1:00 pm, in 489 Minor Hall

​Oxyopia Talk

presented by

Shalin Mehta, PhD
Platform Leader, Advanced Optical Microscopy, Chan Zuckerberg Biohub

Title: Scalable imaging of molecular order and organelle architecture

Abstract: Nanoscale alignment of molecules, or molecular order, underpins the directed functions of cells. The cell’s fascinating capacity of creating order across multiple spatial and temporal scales is illustrated by dynamics of lipid membrane, chromatin, cytoskeleton, and extracellular matrix. The molecular order within cells is too fine to visualize even with super-resolution fluorescence microscopy. Although electron microscopy directly visualizes molecular order, it is limited to fixed cells. Many outstanding structure-function questions in biology require precise, high-resolution, and scalable technologies of imaging molecular order in live cells and tissues.

In this talk, I will discuss advances in polarization microscopy for scalable imaging of molecular order in live cells. We designed instantaneous fluorescence PolScope to measure concentration, alignment, and orientation of biomolecules simultaneously [1]. The instantaneous fluorescence PolScope revealed the dynamic orientation of nanoscale actin filaments within microscale actomyosin network in migrating skin cells [1], previously accessible with electron microscopy only in fixed cells. Instantaneous fluorescence PolScope enabled analysis of ‘active alignment’ of integrin transmembrane receptors at the surface of migrating white blood cells[2] and firboblasts[3]. These two integrins are structurally very different,
yet both types are oriented in a direction dictated by the intracellular actin flow when activated. Such active alignment of cell surface receptors can be analyzed only in live cells with polarized light.

At CZ Biohub, my lab develops computational imaging systems for measurement of order in dynamic three-dimensional specimens. A primary area of application is scalable imaging of virus biogenesis and life cycle in live cells. These technological advances promise new insights in mechanisms of infection and discovery of new therapeutic opportunities.

References:

* Equal contribution

1. Mehta, S. B. et al. Dissection of molecular assembly dynamics by tracking orientation and position of single molecules in live cells. Proc. Natl. Acad. Sci. 113, E6352–E6361 (2016).

2. *Nordenfelt, P. et al. Direction of actin flow dictates integrin LFA-1 orientation during leukocyte migration. Nat. Commun. 8, 2047 (2017).

3. *Swaminathan, V. et al. Actin retrograde flow actively aligns and orients ligand-engaged integrins in focal adhesions. Proc. Natl. Acad. Sci. 114, 10648–10653 (2017).

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