Biology subjects

Proag, A.

Publications and source records attributed to Proag, A..

4 recordsLinked to original sources

bioRxiv2026

Deep-tissue absolute force spectroscopy with sub-piconewton precision

Quantitative measurements performed directly in vivo are necessary to understand how forces shape living tissues, yet this remains challenging due to optical scattering and mechanical complexity. Here, we present a method for making absolute force measurements using nanoscopic optical tweezers with a sensitivity of 300 fN in optically turbid biological media. Our approach combines back focal plane interferometry operating within the optical memory effect regime with a global fluctuation-dissipation fitting framework that simultaneously calibrates position detection, trap stiffness, and viscoelastic response. This method overcomes aberration-induced biases by jointly fitting passive fluctuations and driven harmonic responses, enabling robust force reconstruction in thick, scattering tissues within the mechanically relevant frequency range below 300 Hz. We validate our approach using highly scattering Drosophila pupae and embryos, demonstrating reliable in vivo measurements of forces and mechanical properties. Operating at a 1 kHz acquisition bandwidth, the system captures relevant mechanical dynamics without requiring extended high-frequency detection. Using this framework, we quantify the increase in cortical tension during pupal morphogenesis, characterize tissue viscoelasticity, and reveal stage-dependent variations in nuclear membrane tension during embryogenesis, even in the presence of strong ATP-driven fluctuations. Beyond bulk measurements, our method enables the quantitative mechanical characterization of single cells within mechanically coupled tissues.

bioengineering↗

bioRxiv2021

Elasticity of dense actin networks produces nanonewton protrusive forces

Actin filaments assemble into force-generating systems involved in diverse cellular functions, including cell motility, adhesion, contractility and division. It remains unclear how networks of actin filaments, which individually generate piconewton forces, can produce forces reaching tens of nanonewtons. Here we use in situ cryo-electron tomography to unveil how the nanoscale architecture of macrophage podosomes enables basal membrane protrusion. We show that the sum of the actin polymerization forces at the membrane is not sufficient to explain podosome protrusive forces. Quantitative analysis of podosome organization demonstrates that the core is composed of a dense network of bent actin filaments storing elastic energy. Theoretical modelling of the network as a spring-loaded elastic material reveals that it exerts forces of up to tens of nanonewtons, similar to those evaluated experimentally. Thus, taking into account not only the interface with the membrane but also the bulk of the network, is crucial to understand force generation by actin machineries. Our integrative approach sheds light on the elastic behavior of dense actin networks and opens new avenues to understand force production inside cells.

biophysics↗

bioRxiv2019

Curling of epithelial monolayers reveals coupling between active bending and tissue tension

Epithelial monolayers are two-dimensional cell sheets which compartmentalise the body and organs of multi-cellular organisms. Their morphogenesis during development or pathology results from patterned endogenous and exogenous forces and their interplay with tissue mechanical properties. In particular, bending of epithelia is thought to results from active torques generated by the polarization of myosin motors along their apico-basal axis. However, the contribution of these out-of-plane forces to morphogenesis remains challenging to evaluate because of the lack of direct mechanical measurement. Here, we use epithelial curling to characterize the out-of-plane mechan ics of epithelial monolayers. We find that curls of high curvature form spontaneously at the free edge of epithelial monolayers devoid of substrate in vivo and in vitro. Curling originates from an enrichment of myosin in the basal domain that generates an active spontaneous curvature. By measuring the force necessary to flatten curls, we can then estimate the active torques and the bending modulus of the tissue. Finally, we show that the extent of curling is controlled by the interplay between in-plane and out-of-plane stresses in the monolayer. Such mechanical coupling implies an unexpected role for in-plane stresses in shaping epithelia during morphogenesis.

biophysics↗

bioRxiv2018

Physical and functional cell-matrix uncoupling in a developing tissue under tension

Tissue mechanics play a crucial role in organ development. It relies on cells and extracellular matrix (ECM) mechanical properties, but also on their reciprocal interaction. The relative physical contribution of cells and ECM to morphogenesis is poorly understood. Here, we dissected the mechanics of the envelope of the Drosophila developing leg, an epithelium submitted to a number of mechanical stresses: first stretched, it is then torn apart and withdrawn to free the leg. During stretching, we found that mechanical tension is entirely borne by the ECM at first, then by the cellular monolayer as soon as they detach themselves from one another. Then, each envelope layer is removed by an independent mechanism: while ECM withdraws following local proteolysis, cellular monolayer withdrawal is independent of ECM degradation and driven by an autonomous myosin-II-dependent contraction. These results reveal a physical and functional cell-matrix uncoupling that could timely control tissue dynamics during development.

cell biology↗