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Forces, shape and structure of living cells

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The three-dimensional mechanical balance of living cells is not understood yet, whether they are embedded in a living tissue or cultured in a Petri dish. The objective of this internship is to focus on the simple geometry of cells spreading on a substrate to write in details the mechanical balance, in an analogy with the wetting of liquid droplets.

Living cells possess a cytoskeleton made of polymer chains, which they continuously re-shape, and which are bound together (crosslinked) by transient molecular bonds, lasting for seconds only. Also, other molecular bonds are indeed molecular motors, able to exert contractile (pulling) forces within the cytoskeleton. These forces are transmitted onto the cell’s environment, allowing it to deform its substrate, and, through a yet unclear mechanism, to move.

Using optical microscopy techniques (including fluorescence of key-molecules involved in these mechanisms) jointly with traction force measurements on single cells (microplate device), we have been able to characterise the mechanical behaviour of the cytoskeleton (Mitrossilis et al., 2009 and 2010) and demonstrate that a rheological model (Etienne et al, 2015) can predict the complex behaviours of cell force modulation in response to the surroundings’ stiffness.

However, for the time being our model does not include the mechanisms of force transmission to the substrate via cell adhesion. The aim of this internship is to explore the possibilities of modelling the contribution of adhesion, using experimental results allowing visualisation of the adhesion zones geometry simultaneously with force measurement (Fouchard et al, 2014). This internship is a preliminary for a PhD project that will involve both experiments and modelling to understand this function. The PhD candidate will benefit from the expertise of both the LIPHY group (modelling, traction force microscopy, AFM), and MSC (microplate experiments, drug-targetting of intracellular molecular mechanisms).

The intern will receive an allowance of circa 540€ per calendar month.
Please contact us for further details.

Contacts : :
Jocelyn Etienne : http://www-liphy.ujf-grenoble.fr/jocelyn-etienne
Atef Asnacios : http://www.msc.univ-paris-diderot.fr/~atef_asnacios/index_fr.html