Biology subjects

Savy, T.

Publications and source records attributed to Savy, T..

7 recordsLinked to original sources

bioRxiv2026

Mechanical and Growth Anisotropy in Chara corallina: Challenging Green's Hypothesis

Paul Green hypothesized that growth anisotropy of plant cylindrical organs could be controlled by cell-wall elastic strain. The present study aimed to challenge this hypothesis through a robust experimental and analytical framework. By combining live-cell imaging of C. corallina internodal cells with controlled turgor pressure manipulation, we simultaneously measured, for the first time, both the growth strain rate tensor and the elastic compliance tensor derived from multiaxial mechanical testing in the same cell. Under Greens hypothesis, a significant correlation should be observed between the two tensors in all directions. Our results revealed a moderate yet significant correlation between multiaxial elastic compliances and growth strain rates most pronounced in the axial direction. The ratio of axial-to-radial elastic compliance was significantly correlated with the ratio of radial-to-axial growth strain rates. In contrast, other quantities, such as the radial compliance components or the orientations of the two tensors relative to the cell axis showed no significant correlation. Furthermore the growth strain rate tensor was strongly age-dependent in both magnitude and orientation, unlike the elastic compliance. Finally, analysis of intra-tensor variability revealed that axial and radial components were strongly correlated for both tensors, with a lowered correlation in the principal axis decomposition.

plant biology↗

bioRxiv2025

Endothelin 3 and T-type Ca2+ channels drive enteric neural crest cell calcium activity, contractility and migration

Enteric neural crest cells (ENCCs) colonize the gut during embryogenesis and migration defects give rise to Hirschsprung disease (HD). Mutations in GDNF/RET and EDN3/EDNRB are known to be causal in HD. Here, we show that migrating ENCCs in mice exhibit endogenous EDN3/EDNRB-gated calcium activity, mediated by chloride channels, T-type Ca2+ channels and inositol trisphosphate-sensitive intracellular-store release. We find that inhibiting Ca2+ activity results in ENCC migration defects, while exciting it promotes migration by increasing ENCC contractility and traction force to the extracellular matrix. Our study demonstrates that embryonic endothelin-mediated neural crest migration and adult endothelin-mediated vasoconstriction is one and the same phenomenon, taking place in different cell types. Our results suggest a functional link between rare mutations of CACNA1H (the gene encoding CaV3.2) and HD, and pave the way for understanding neurocristopathies in terms of neural crest cell bioelectric activity deficits.

developmental biology↗

bioRxiv2025

Resilience in zebrafish embryoids

It is unresolved how morphogenetic cell movements and Nodal signalling are involved in the formation of the embryonic body during gastrulation. We address this question by using the zebrafish embryoid model system, which consists of cultured blastula cells lacking yolk and signalling derived from the yolk syncytial layer (YSL). Zebrafish embryoids form a cylindrical-like structure under serum-free growth culture conditions. We find that embryoids elongate without directed convergence and maintain their proliferation rate and cell mixing behaviour. Surprisingly, they undergo budding activity that has not been reported in zebrafish embryos yet. Here, the constitutively active Nodal receptor type I promotes internalisation-like gastrulation movements and induces the expression of shield genetic markers in embryoids. This work demonstrates that the absence of the yolk and signalling derived from the YSL does not affect the cell behaviour, while the constitutively active Nodal receptor type I impacts budding, internalisation movement and the emergence of the second shield. Summary statementWe demonstrate that the cell behaviour during gastrulation is robust to the deficiency of yolk topology and signalling originating from the yolk syncytial layer.

developmental biology↗

bioRxiv2024

Mechanical constraints organize 3D tissues and orchestrate muscle differentiation

Biological tissues achieve proper shape and ordered structures during development through responses to internal and external signals, with mechanical cues playing a crucial role. These forces guide cellular organization, leading to complex self-organizing structures that are foundational to embryonic patterns. Emerging theories and experiments suggest that "topological morphogens" drive these processes. Despite the predominance of three-dimensional (3D) structures in biology, studying 3D tissues remains challenging due to limited model systems and the complexity of modeling. Here, we address these challenges by using self-organized cellular aggregates, specifically spindle-shaped C2C12 myoblasts, subjected to controlled mechanical stretching. Our findings reveal that these cells form a multilayered, actin-oriented tissue structure, where mechanical forces drive long-range 3D organization and muscle differentiation. Notably, tissue surface emerges as a hotspot for differentiation, correlating with directional order as shown by single molecule fluorescent in situ hybridization. Significance StatementWe explore how cells work together to form complex structures, particularly in 3D, using muscle precursors cells (C2C12 myoblasts) as a model. By applying controlled stretching forces, we found that these cells self-organize into layered tissues that guide their transformation into muscle. This research highlights the critical role of physical forces in shaping tissues, suggesting that the way cells are physically arranged and stretched in three dimensions can significantly influence their behavior and function. Our findings offer new insights into how tissues develop and could have implications for tissue engineering, where creating the right 3D environment is key to successful tissue growth and repair.

biophysics↗

bioRxiv2023

Dynamic fate map of hindbrain rhombomeres in zebrafish

Understanding of the morphogenetic processes that underlie the patterning of the vertebrate hindbrain requires establishment of rhombomere (r) cell lineages. Using long term in vivo two-photon imaging of zebrafish transgenic lines and automated image processing tools, we provide a method to reconstruct the r2-r6 lineage trees from the onset of gastrulation through early neurulation. We provide a dynamic fate map of hindbrain patterning at single-cell resolution. We show that rhombomere progenitor domains are aligned along the anteroposterior (AP) and dorsoventral (DV) axes as early as the shield stage. Rhombomere progenitor domains show a segmental organization, parallel to the blastoderm margin that predicts the future AP order of hindbrain. The DV organization of rhombomeres is set by the segregation of the progenitors along the DV axis of the embryo. Progenitors located at the dorsal/medial part of the blastoderm form the ventral domain of the rhombomeres while the lateral progenitors constitute the dorsal part. Our study sheds light on the clonal origin of individual rhombomeres, spatial and temporal patterns of cell division and migration of rhombomere progenitors throughout the early steps of hindbrain morphogenesis.

developmental biology↗

bioRxiv2020

Quantification of cell behaviours and computational modelling show that cell directional behaviours drive zebrafish pectoral fin morphogenesis

MotivationUnderstanding the mechanisms by which the zebrafish pectoral fin develops is expected to produce insights on how vertebrate limbs grow from a 2D cell layer to a 3D structure. Two mechanisms have been proposed to drive limb morphogenesis in tetrapods: a growth-based morphogenesis with a higher proliferation rate at the distal tip of the limb bud than at the proximal side, and directed cell behaviors that include elongation, division and migration in a nonrandom manner. Based on quantitative experimental biological data at the level of individual cells in the whole developing organ, we test the conditions for the dynamics of pectoral fin early morphogenesis. ResultsWe found that during the development of the zebrafish pectoral fin, cells have a preferential elongation axis that gradually aligns along the proximodistal axis (PD) of the organ. Based on these quantitative observations, we build a center-based cell model enhanced with a polarity term and cell proliferation to simulate fin growth. Our simulations resulted in 3D fins similar in shape to the observed ones, suggesting that the existence of a preferential axis of cell polarization is essential to drive fin morphogenesis in zebrafish, as observed in the development of limbs in the mouse, but distal tip-based expansion is not. AvailabilityUpon publication, biological data will be available at http://bioemergences.eu/modelingFin, and code source at https://github.com/guijoe/MaSoFin. Contactjoel.dokmegang-kassap@stu.mmu.ac.uk, nadine.peyrieras@cnrs.fr or rene.doursat@iscpif.fr Supplementary informationSupplementary data are included in this manuscript.

systems biology↗

bioRxiv2018

Cdh2 coordinates Myosin-II dependent internalisation of the zebrafish neural plate

Tissue internalisation is a key morphogenetic mechanism by which embryonic tissues generate complex internal organs and a number of studies of epithelia have outlined a general view of tissue internalisation. Here we have used quantitative live imaging and mutant analysis to determine whether similar mechanisms are responsible for internalisation in a tissue that apparently does not have a typical epithelial organisation - the zebrafish neural plate. We found that although zebrafish embryos begin neurulation without a conventional epithelium, medially located neural plate cells adopt strategies typical of epithelia in order to constrict their dorsal surface membrane during cell internalisation. Furthermore, we show that Myosin-II activity is a significant driver of this transient cell remodeling which also depends on Cdh2 (N-cadherin). Abrogation of Cdh2 results in defective Myosin-II distribution, mislocalised internalisation events and defective neural plate morphogenesis. Our work suggests Cdh2 coordinates Myosin-II dependent internalisation of the zebrafish neural plate.

developmental biology↗