Almost all eukaryotic cells use actins for multiple vital processes. Cells move, divide, organize their interior, and establish and maintain their shape with the help of actins filaments. Repeated, identical subunits similar across cell types make up these filaments. Despite the common nature of the filaments, cells co-opt them for multifarious tasks with a spectrum of proteins to nucleate, cap, sever, branch, cross-link, and move along them. This work aims both (i) to understand how cells employ actins for specific tasks and (ii) to push our understanding of the actins system towards a physical picture expressed by predictive mathematical models. This study focuses on fission yeast as a model eukaryotic cell. The proposed approach combines mathematical modeling, image analysis, and experimental biology to study how cells organize actins. Two hypotheses form the basis of the study. First, that cross-linking proteins aid the formation of a ring that divides the cytoplasm during the final step of division. Second, that nucleating proteins and severing proteins act in concert with confinement to organize actins into cables. The study proposes to test these hypotheses by (i) extracting relevant quantities from micro- scope images of these structures, (ii) building mathematical models of these structures emphasizing measurable quantities, and (iii) collaborating with experimentalists to subject these models to rigorous challenges. The image analysis uses novel tools, such as tools for automated filament and filament-network tracking, developed in collaboration with computer scientists. The mathematical modeling makes use of a combination of discrete and continuum approaches to dynamical systems informed by experimental parameters. The experimental chal- lenges come in collaboration with Jian-Qiu Wu's lab and in the form of genetic manipulations, pharmacological treatments, and fluorescence microscopy. Every aspect of the study leads to a mechanistic understanding of the actins cytoskeleton and its roles that would underpin future cancer and health research based on an advanced understanding of cellular function.

Public Health Relevance

This project uses mathematical modeling, image analysis, and experimental biology to study the actins cy- toskeleton, a dynamic structure underlying the growth and division of all human cells. If successful, this basic science would underpin future cancer and health research based on an understanding of cellular function.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Modeling and Analysis of Biological Systems Study Section (MABS)
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Gindhart, Joseph G
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Lehigh University
Schools of Arts and Sciences
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Tang, Haosu; Laporte, Damien; Vavylonis, Dimitrios (2014) Actin cable distribution and dynamics arising from cross-linking, motor pulling, and filament turnover. Mol Biol Cell 25:3006-16
Xu, Ting; Vavylonis, Dimitrios; Huang, Xiaolei (2014) 3D actin network centerline extraction with multiple active contours. Med Image Anal 18:272-84
Bidone, Tamara C; Tang, Haosu; Vavylonis, Dimitrios (2014) Dynamic network morphology and tension buildup in a 3D model of cytokinetic ring assembly. Biophys J 107:2618-28
Li, Fengqiang; Xu, Ting; Nguyen, Duc-Huy T et al. (2014) Label-free evaluation of angiogenic sprouting in microengineered devices using ultrahigh-resolution optical coherence microscopy. J Biomed Opt 19:16006
Drake, Tyler; Vavylonis, Dimitrios (2013) Model of fission yeast cell shape driven by membrane-bound growth factors and the cytoskeleton. PLoS Comput Biol 9:e1003287