Laboratoire Matière et Systèmes Complexes

Coupling reaction-diffusion to cell shape to unravel emergent cell signalling behaviour

Dr Stan Maree
Computational and Systems Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, United Kingdom

Pattern formation through reaction-diffusion of proteins is core to establishing functionally distinct domains within cells. In fact, cells are able to be in either a “rest state”, in which such proteins are distributed homogeneously along its interior, or in a “polarised” state, in which clear domains are established. This phenomenon of polarisation also allows cells to change shape. Animal cell motility is driven by the formation of such domains, while plant cells, encased in a rigid cellulose cell wall, use them for cell shape changes and polar transmission of signals. Molecular studies reveal that even though plants and animals diverged 1.6 billion years ago, they still share a similar core machinery required for cell shape changes. A fascinating similarity between animal and plant cells with respect to the organisation of cytoskeletal elements in the regions of active protrusive growth and cell wall extension (the `leading edges’), is paralleled by a striking conserved molecular mechanism responsible for the creation and organisation of these `leading edges’. To unravel and understand the interplay and feedbacks which brings about cell motility, we have previously developed a multiscale model of a motile keratocyte, describing how the reaction-diffusion module can be biophysically coupled to the cells’ deformation. We contrast this to the cell shape changes that occur in the pavement cells (PCs) in the leaves : PCs grow multiple lobes, which fit perfectly into the indentations of the neighbouring cells, generating interdigitating, jigsaw-like patterns. We will show that similar modular principles as found in the keratocyte play a role. We then use both systems to show how polarity formation can also be used as an integrator for sensing external cues : in the case of the keratocyte, it is used for navigation ; in the case of the plant cells, it not only underlies the establishment of cell-to-cell coordination, but even long-range tissue polarity. Hence, cell signalling can be seen as an outcome of feedbacks between intracellular reaction-diffusion patterning, cell shape dynamics and external signals.