Bilateral BBSRC-NSF/BIO: Excitocell: A rewired eukaryotic cell model for the analysis and design of cellular morphogenesis

Regents Of The University Of Michigan - Ann Arbor, Ann Arbor MI

Investigators

Abstract

Virtually every important thing cells and tissues do involve changes in cell morphology: cell division, cell migration, and wound healing all involve profound changes in cell shape. These shape changes are powered by the outer layer of the cell, which is called the "cortex". The cortex contains a meshwork of fibrous proteins that can contract, protrude, and slide. These movements provide the basis of cell shape changes. The control of this fibrous network is the domain of a protein called Rho. Rho is somehow activated in distinct patterns, each of which corresponds to a different cell shape change. Thus, in order to understand and control processes such as cell division, cell migration and wound healing, it is essential to learn how to understand and control patterns of Rho activation. In this collaborative project, investigators from the US and the UK use synthetic cell biology and mathematical modeling to test mechanisms underlying cortical pattern formation. This project will provide research opportunities for interdisciplinary training at the interface between quantitative cell biology and mathematical modeling for undergraduates, graduate students, and postdocs. The project also offers embedded research opportunities for high-school teachers as well as topic-specific K-12 and public outreach activities. Previous studies by the PIs demonstrated that cells can support sustained waves of dynamically-coupled Rho activity and actin assembly, and mathematical modeling followed by experimental verification revealed that cortical wave propagation is based on Rho autoactivation and actin-mediated Rho inactivation. This constitutes the basis of an "excitable" system, a family of well-established theoretical models with few previously-known cellular manifestations. This project will deduce and experimentally validate a minimal molecular mechanism and basic design elements required for cortical excitability. To achieve the goals of this project, a novel semi-synthetic platform for replicating complex cell behaviors using simple macromolecular parts will be employed, enabling manipulation of the molecular network at escalating complexity instead of by dissecting a complex physiological network. The project will couple computational modeling of excitable dynamics to live-cell imaging in whole cells and in a new ex vivo model of cortical dynamics. First, excitable dynamics will be reconstituted in resting, non-mitotic cells (oocytes of frogs and echinoderms) using natural regulators and their mutants, followed by their replacement with synthetic equivalents. Second, a quantifiable ex vivo model will be developed (using frog oocyte or egg extracts and supported lipid bilayers) that permits precise control of system composition in a simplified context. Third, to achieve on-demand control of cortical pattern formation, an optogenetic approach in animal oocytes will be used to explore the repertoire of both natural and synthetic cortical pattern formation. Iterative experimentation and computational modeling will be employed throughout the project to 1) interpret biological data, 2) express candidate mechanisms in the form of mathematical models, 3) generate predictions, and 4) test those predictions experimentally.