Calcium Spikes in Epithelium: study on Drosophila early embryos

International audienceCalcium ion acts in nearly every aspect of cellular life. The versatility and specificity required for such a ubiquitous role is ensured by the spatio-temporal dynamics of calcium concentration variations. While calcium signal dynamics has been extensively studied in cell cultures and adult tissues, little is known about calcium activity during early tissue morphogenesis. We monitored intracellular calcium concentration in Drosophila gastrula and revealed single cell calcium spikes that were short-lived, rare and showed strong variability among embryos. We quantitatively described the spatio-temporal dynamics of these spikes and analyzed their potential origins and nature by introducing physical and chemical perturbations. Our data highlight the inter-and intra-tissue variability of calcium activity during tissue morphogenesis

Probing cell-surface dynamics and mechanics at different scales

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Molecular clustering in the cell: from weak interactions to optimized functional architectures

International audienceMolecular components of the cell, such as lipids, proteins or RNA molecules, can associate through weak interactions and form clusters. A growing number of studies have shown that clustering of molecules is crucial for cell functions such as signal optimization and polarization. Clustering provides an intermediate level of organization between the molecular and cellular scales. Here we review recent studies focusing on how molecular clustering functions in different biological contexts, the potential importance of clustering for information processing, as well as the physical nature of cluster formation. We mainly refer to literature focusing on clusters within cell membranes, but also report findings on clusters in the cytosol, emphasizing their ubiquitous role

Calcium signaling in developing embryos: focus on the regulation of cell shape changes and collective movements

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Physics puzzles on membrane domains posed by cell biology

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Learning the mechanobiology of development from gastruloids

International audienceGastruloids acquire their organization and shape through cell biochemical and mechanical activities. Such activities determine the physical forces and changes in material properties that transform simple spherical aggregates into organized tissues. In this Perspective, we discuss why the concepts and approaches of mechanobiology, a discipline that focuses on cell and tissue mechanics and its contribution to the organization and functions of living systems, are essential to the gastruloid field and, in turn, what gastruloids may teach us about mechanobiology

Sculpting tissues by phase transitions

International audienceBiological systems display a rich phenomenology of states that resemble the physical states of matter - solid, liquid and gas. These phases result from the interactions between the microscopic constituent components - the cells - that manifest in macroscopic properties such as fluidity, rigidity and resistance to changes in shape and volume. Looked at from such a perspective, phase transitions from a rigid to a flowing state or vice versa define much of what happens in many biological processes especially during early development and diseases such as cancer. Additionally, collectively moving confluent cells can also lead to kinematic phase transitions in biological systems similar to multi-particle systems where the particles can interact and show sub-populations characterised by specific velocities. In this Perspective we discuss the similarities and limitations of the analogy between biological and inert physical systems both from theoretical perspective as well as experimental evidence in biological systems. In understanding such transitions, it is crucial to acknowledge that the macroscopic properties of biological materials and their modifications result from the complex interplay between the microscopic properties of cells including growth or death, neighbour interactions and secretion of matrix, phenomena unique to biological systems. Detecting phase transitions in vivo is technically difficult. We present emerging approaches that address this challenge and may guide our understanding of the organization and macroscopic behaviour of biological tissues