Speaker:

Alexandra Jilkine, Assistant Professor, Department of Applied & Computational Math & Statistics, University of Notre Dame

Title:

Models of Diffusion-Coupled Oscillators in Cell Biology

Abstract:

One of the major tasks that a cell faces during its lifecycle is how to spatially localize its components. Correct spatial organization of various proteins (cellular polarity) is fundamental not only for the correct cell shape, but also to carry out essential cellular functions, such as the spatial coordination of cell division. We present a mathematical model of the core mechanism responsible for the regulation of polarized growth dynamics in the model organism, fission yeast. The model is based on the competition of growth zones of polarity protein Cdc42 localized at the cell tips for a common substrate (inactive Cdc42) that diffuses in the cytosol. We consider several potential ways of implementing negative feedback between Cd42 and its GEF in this model that would be consistent with the observed oscillations of Cdc42 in fission yeast. We analyze the bifurcations in this model as the cell length increases, and total amount of Cdc42 and GEF increase. We find that a stable oscillation and a stable steady state can coexist, which is consistent with the experimental finding that only 50% of bipolar cells oscillate. Our model suggests that negative feedback is more likely to be acting through inhibition of GEF association rather than upregulation of GEF dissociation. We consider the differences between the deterministic and stochastic versions of the model, and discuss general conditions for how diffusion can trigger collective synchronous oscillations.

Speaker Bio:

Alexandra Jilkine is an Assistant Professor in the Department of Applied and Copmutational Mathematics and Statistics at the University of Notre Dame. She obtained her Ph.D. in Applied Mathematics from University of British Columbia in 2010. Prof. Jilkine is a mathematical biologist, and her research interests include: mathematical modelling of cell lineages and optimal division patterns for delaying cancer, modeling feedbacks governing stem cell renewal and differentiation, and spatiotemporal behaviour of biochemical circuits.

About the Speaker Series:

Wednesdays@NICO is a vibrant weekly seminar series focusing broadly on the topics of complex systems and data science. It brings together attendees ranging from graduate students to senior faculty who span all of the schools across Northwestern, from applied math to sociology to biology and every discipline in-between.

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