Current and Past Research Activities

Physics of somite formation

Tissue patterning is a fundamental step in embryonic development, establishing the boundaries and organization from which organs emerge. This process requires the integration of biochemical signaling and mechanical forces to generate robust structures at the right place and time. A striking example is the segmentation and shaping of somites during early vertebrate development. Somites form periodically as segments bud from the anterior end of the presomitic mesoderm, concomitant with its mesenchymal-to-epithelial transition. The physical mechanisms that drive this tissue-scale patterning and shape emergence remain poorly understood.

We investigate how mechanical forces and biochemical signaling are integrated to drive tissue patterning and shape emergence. Using the chicken embryo as a model system, we focus on axial segmentation and somite formation, combining experimental embryology with quantitative and theoretical approaches. We develop methods to measure and manipulate tissue mechanics and investigate how collective cell behaviors give rise to somite shape and pattern. A central theme of our work is to view the mesoderm as an active material, in which cellular dynamics and interactions generate tissue-scale organization.

This interdisciplinary approach brings together developmental biology, quantitative biophysics, microfabrication, and modeling to uncover the physical principles governing embryonic morphogenesis.

Axial elongation in chicken embryos

Cell diffusion profile along the axis

In this project, we study cell dynamics and mesodermal mechanics during the axis elongation process in chicken embryo. By combining experiments with cell tracking and physical modelling, we show that cells in the paraxial mesoderm move randomly. We can define an effective diffusion for these cells originating from their activity that is coupled to the morphogen gradients along the axis. We show that treating the mesoderm as an active fluid with proper boundary condition can account for the observed axial elongation. The fluid behavior of the paraxial mesoderm was established through rounding and micropipette aspiration experiments. In parallel, we show that this elongation is autonomous to the paraxial mesoderm, as explants of the mesoderm elongate in groove shaped channels.

Mechano-responses of embryonic tissues in vitro


We study the mechanics of in vitro multicellular systems, like tissue explants and cellular aggregates, using techniques such as micropipette aspiration, to determine their rheology and their active responses to applied external stresses. We also investigate how such systems behave when put on adhesive substrates. Following their spreading dynamics, we can assess the role of cytoskeletal and intercellular components interfering with this process.

Biomimetic cells

Hydrodynamic tube extrusion from a biomimetic cell

Using a minimal biomimetic system, we explore how actin cortex might modify the mechanics of a cell’s plasma membrane. First, an actin shell is polymerized at the inner layer of a Giant Unilamellar Vesicle (GUV, aka a liposome), and then, the effect of the cortex on the mechanics of the membrane is studied. At constant force (hydrodynamic tube pulling technique), membrane nanotubes pulled from such systems show a drastic difference compared to GUVs lacking a cortex, suggesting the formation of domains, known as corals, which limit drastically the lipid area available for membrane nanotubes.

Swimming Paramecium in magnetic fields

Any biological matter (70% water) can be levitated with a strong magnet, thanks to its diamagnetic properties. By exploiting this diamagnetic levitation principle, we developed a setup, using inhomogeneous intense magnetic fields, to apply pulling and pushing forces to cells. We studied the role of these simulated gravitational forces on the swimming Paramecia, and showed that they actively regulate their swimming speed in response to the strength of the gravitational force. We also showed that homogenous fields, i.e. no force, the swimming speed did not change, but the trajectories were aligned with the field direction.