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Multilevel approach to cell and tissue polarity and traffic jams

Presented by: 
Veronica Grieneisen
Wednesday 9th December 2015 - 09:00 to 10:00
INI Seminar Room 1
In this talk I wish to compare and contrast cell and tissue polarity between very diverse organisms. Computational approaches combined with molecular studies and in vivo microscopy were necessary to reveal how polarity is coordinated and linked on three different levels: on the scale of the tissue, the cellular and subcellular tissue level. At the single cell level, a spatially uniform activation and patterning of GTPases can cause polarity to emerge spontaneously, independent of spatial pre-patterns or localized polarizing signals. We argue that plants and animals have inherited this same “unicellular mode” of establishing cell polarity, and that multicellular coordination has thereafter diverged using this underlying mechanism as a building block: Being capable of intracellular partitioning, neighbouring plant cells that are separated by cell wall then coordinate their polarities - through indirect cell-cell coupling. This is resultant from changes in concentration level of a phytohormone, auxin, inbetween and along cells.

In the specific case of pavement cells of leaves (jigsaw-shaped cells with interlocking lobes and indentations), this phenomenon comes about as interdigitation, and requires the opposite response of identical neighbouring cells to the same local auxin signal in the cell wall, between the cells. Our theoretical work identifies key requirements for such indirect cell-cell signalling that that gives rise to correct interdigitation. These requirements, based on known molecular interactions, can then be extrapolated to other multi-cellular tissues, to understand the interdependency between cell and tissue polarity.

Extrapolating these findings we further show how animal cells, capable of direct cell-cell coupling, can establish, through similar principles, robust tissue coordination. In the end of our talk, I will also show how established tissue polarity in plants requires extra conditions of regulation, to avoid issues of traffic jam in relation to nutrient uptake.

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University of Cambridge Research Councils UK
    Clay Mathematics Institute London Mathematical Society NM Rothschild and Sons