Single-Cell Biophysics: Measurement, Modulation, and Modeling

Single-Cell Biophysics: Measurement, Modulation, and Modeling

Monday Speaker Abstracts

Single-Molecule Study of the Chromatin Structure and Dynamics Yujie Sun Biodynamics Optical Imaging Center, Peking University, China No Abstract

Emerging Role of Differential Molecular Association in Force-transmitting Nascent Adhesions Sangyoon J. Han 1 , Alexia Bachir 4 , Kevin Dean 1 , Edgar Gutierrez 3 , Alex Groisman 3 , Alan R. Horwitz 2,4 , Gaudenz Danuser 1 . 2 Allen Institute for Cell Science, Seattle, WA, USA, 1 University of Texas Southwestern Medical Center, Dallas, TX, USA, 3 University of California San Diego, San Diego, CA, USA, 4 University of Virginia, Charlottesville, VA, USA. Adhesion dynamics play a critical role in cell migration, whose decision process is affected by lots of biochemical and biomechanical inputs. Adhesions and their coupling with mechanical force have been extensively characterized at the level of large, mature focal adhesions. However, it has been elusive whether the nascent adhesions (NAs), before they reach their full maturation, are able to transmit forces and how these forces, if exist, affect the recruitment of early adhesion molecules. Here, we investigated how the mechanical force and the molecular recruitment of talin, vinculin and paxillin synergistically affect the adhesion assembly using high-resolution traction force microscopy (TFM) and fluorescence imaging of each molecule with eGFP. We used the single-particle-tracking of all NAs, extracted kinematic and kinetic features from the tracks, and used human-in-the-loop machine learning to identify the sub-population of nascent adhesions that assemble and disassemble at the protruding cell edge. We report that about 60% of non-maturing NAs transmit forces during their average lifetime of 2 minutes. Via time-lag analysis between eGFP-intensity and force, we show distinct difference in the recruitment sequences of three molecules in between non-maturing NAs vs. maturing NAs. Talin was recruited ~7 sec before vinculin’s recruitment to the adhesions complex in maturing NAs whereas the two molecules were recruited at the same time in non-maturing NAs. Moreover, vinculin’s early assembly rate to the maturing NAs was higher than in non-maturing NAs whereas talin and paxillin have shown no difference in early assembly. Traction force growth rate in the maturing vinculin complex was also higher than that in non-maturing vinculin complex. Together, these findings suggest a pre-conditioning role of talin’s early recruitment to promote faster vinculin recruitment and force transmission for successful adhesion maturation, possibly via effective stretching.

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