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Mechanobiology of Disease
Friday Speaker Abstracts
41
Mechanics of Embryonic Zebrafish Revealed by Magnetically Applied Local Forces
Radu Tanasa
1
, Julien Dumortier
2
, Craig Russell
3
, Qian Cheng
1
, Richard Adams
2
, Alexandre
Kabla
1
.
1
University of Cambridge, Cambridge, United Kingdom,
2
University of Cambridge, Cambridge,
United Kingdom,
3
University of Cambridge, Cambridge, United Kingdom.
The path from a single cell to a complex organism is the result of fine and synchronized
movements of cells and tissues, including tissue reshaping like convergence and extension,
internalization, collective cell migration. A wealth of studies indicate that this supra cellular
remodelling is dependent upon careful control of the physical properties of these tissues. While
such properties are easily accessible in cell culture or in explants, it remains a challenge to
measure mechanical properties in vivo, within the embryo. Here, we propose a method to probe
the physical properties of early zebrafish embryo using grafted superparamagnetic beads. Beads
are manipulated with a four-pole electromagnetic tweezers, arranged in a tetrahedron
configuration. This geometry secures a very accurate control of generated forces in magnitude
(nanoNewton range) and direction. The resultant three-dimensional bead movement and the
shapes of surrounding cells are spatially (submicron) and temporally (seconds) resolved by a
light sheet fluorescence microscope (SPIM). We interpret tissue response to repeatedly applied
forces within the framework of a linear viscoelastic model. To validate our technique, we chose
to focus on the pre-gastrulation blastodermal tissue, a relative simple morphogenetic transition,
before more complex movements begin, which might complicate the interpretation of the results.
Before the onset of gastrulation, the embryo goes from an ellipsoid to a spherical shape. We
show that this event is dominated by random cell migration accompanied by a notable change of
mechanical properties at both cell and tissue levels. We discuss our results in terms of cell
motility, cell adhesion and cell stiffness, which are known to be dependent respectively on Rac1,
E-Cadherin and MyosinII activities. We see that mechanical properties, cell migration and
morphogenesis are linked and impact each other, even at this simple early stage of embryonic
development.