Biology subjects

Peyrieras, N.

Publications and source records attributed to Peyrieras, N..

7 recordsLinked to original sources

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↗

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↗

bioRxiv2020

Cytokinetic abscission is part of the mid-blastula transition switch in early zebrafish embryogenesis

Animal cytokinesis ends with the formation of a thin intercellular membrane bridge connecting the two newly formed sibling cells that is ultimately resolved by abscission. While mitosis is completed within 15 minutes, the intercellular bridge can persist for hours, maintaining a physical connection between sibling cells and allowing exchange of cytosolic components. Although cell-cell communication is fundamental for development, the potential role of intercellular bridges during embryogenesis have not been fully elucidated. Here, we found that in early zebrafish (Danio rerio) embryogenesis, abscission is delayed and cells do not resolve their intercellular bridges until midblastula transition (MBT), giving rise to the formation of small inter-connected cell clusters. Interestingly, abscission commences during the MBT switch, which is manifested by cell cycle elongation, loss of synchronized divisions and genome activation. Moreover, depletion of Chmp4bb which is an essential ESCRT-III component for scission, delayed abscission beyond the MBT switch. Hallmark features of MBT, including transcription onset and cell shape changes, were similar in sibling cells connected by intercellular bridges, proposing a role for intercellular bridges in maintaining cell-cell communication in the embryo. Taken together, our data suggest that abscission is part of the cellular changes that occur during MBT and that cells coordinate their behavior during this critical embryonic phase through persisted intercellular bridges. Significance StatementIn this work we show that the last step of cytokinesis, termed abscission, is inhibited in early zebrafish embryos. As a result, sibling cells remain connected to one another for several cycles and mutually time their developmental progress including transcription onset. Abscission commences at the 10th cell cycle, when embryos enter the midblastula transition (MBT) switch in which embryonic cells become individualized and exhibit the characteristics of mature cells. Our data suggest that abscission is part of the MBT switch and that embryonic sibling cells mutually time their developmental progress by maintaining physical connections between them in the early embryo.

developmental biology↗

bioRxiv2019

A cis-regulatory change underlying the motor neuron-specific loss of terminal selector gene expression in immotile tunicate larvae

The evolutionary history of animal body plans cannot be fully reconstructed without considering the roles of both novelties and losses. Some of the more remarkable examples of massively parallel evolutionary losses in animals comes from many species in the tunicate genus Molgula that have independently lost the swimming larva and instead develop as tail-less, immotile larvae that bypass the period of swimming and dispersal observed in other tunicates, marine invertebrate chordates that alternate between motile larval and sessile adult life cycle stages. The larvae of Molgula occulta and other tail-less species do not fully develop structures that are essential for swimming behavior, including notochord, tail muscles, and otolith, and loss-of-function mutations have been identified in various genes required for the differentiation of these tissues. However, little is known about the extent of development of the larval nervous system in M. occulta. While differentiated neurons might in principle be entirely dispensable to the non-swimming larva, the adult has a fully functional nervous system like any other tunicate. To further investigate this conundrum, we studied the specification and patterning of the M. occulta Motor Ganglion, which is the key central nervous system compartment that drives the motor movements of swimming tunicate larvae. We found that the expression patterns of important regulators of MG neuron subtype specification are highly conserved during the development of the non-swimming larvae of M. occulta, suggesting that the gene networks regulating their expression are largely intact in this species, despite the loss of swimming ability. However, we identified a M. occulta-specific reduction in expression of the important motor neuron terminal selector gene Ebf (Collier/Olf/EBF or COE) in the Motor Ganglion. Although M. occulta Ebf is predicted to encode a fully functional protein, its expression was reduced in developing motor neurons when compared to species with swimming larvae, which was corroborated by measuring allele-specific expression of Ebf in interspecific hybrid embryos produced by crossing M. occulta with the closely related swimming species M. oculata. Comparative reporter construct experiments also revealed a specific cis-regulatory sequence change that underlies the reduced expression of M. occulta Ebf in motor neurons, but not in other tissues and cell types. This points to a potential mechanism for arresting larval motor neuron differentiation in the non-swimming larvae of this species.

evolutionary biology↗

bioRxiv2019

A contractile acto-myosin belt promotes growth anisotropy during the early stages of pectoral fin development in zebrafish.

The zebrafish pectoral fin is an in vivo model for vertebrate limb formation, well suited to investigate the integration of molecular and cellular dynamics, the results of which translate into shaping the limb bud. We used the ratio between the lengths of the anterior-posterior (AP) and dorso-ventral (DV) axes as the descriptor of how fin shape changes over time. We showed that fin shape transitions from close to hemi-spherical (ratio 1. 36 {+/-} 0.11) to semi-ellipsoid (ratio 1.64 {+/-} 0.04) between 33 and 46 hours post fertilization (hpf). This shape transition coincided with the formation of a contractile \"actin belt\" at the distal rim of the fin bud along its AP axis. The actin belt emerged from a central position and expanded on both sides along the distal rim of the fin, thus marking the DV boundary between two rows of ectodermal cells. Formation of the actin belt depended on Rac protein activity, as suggested by FRET measurements using a Rac biosensor. 3D+time imaging of the developing fin in Rac-deficient embryos showed that anisotropic growth of the fin depends on the actin belt. Indeed, actin belt formation was dramatically reduced or even absent in the embryos without proper Rac activity. This correlated with isotropic growth of the fin bud from normal shape at 33 hpf to quasi hemispherical shape with AP/DV ratio ~1 13 hours later, without affecting cell number and overall bud volume. We propose that the formation of a contractile acto-myosin belt is essential to drive the pectoral fins early anisotropic growth.

developmental 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↗