scholarly journals A tensile ring drives tissue flows to shape the gastrulating amniote embryo

Science ◽  
2020 ◽  
Vol 367 (6476) ◽  
pp. 453-458 ◽  
Author(s):  
Mehdi Saadaoui ◽  
Didier Rocancourt ◽  
Julian Roussel ◽  
Francis Corson ◽  
Jerome Gros
Keyword(s):  
Cell Division ◽  
Simple Model ◽  
Large Scale ◽  
Fluid Motion ◽  
Primitive Streak ◽  
Early Embryo ◽  
Tissue Morphogenesis ◽  
Mesoscopic Scale ◽  
Avian Embryos ◽  
Embryonic Disk

Tissue morphogenesis is driven by local cellular deformations that are powered by contractile actomyosin networks. How localized forces are transmitted across tissues to shape them at a mesoscopic scale is still unclear. Analyzing gastrulation in entire avian embryos, we show that it is driven by the graded contraction of a large-scale supracellular actomyosin ring at the margin between the embryonic and extraembryonic territories. The propagation of these forces is enabled by a fluid-like response of the epithelial embryonic disk, which depends on cell division. A simple model of fluid motion entrained by a tensile ring quantitatively captures the vortex-like “polonaise” movements that accompany the formation of the primitive streak. The geometry of the early embryo thus arises from the transmission of active forces generated along its boundary.

scholarly journals A tensile ring drives tissue flows to shape the gastrulating amniote embryo

2018 ◽  
Author(s):  
Mehdi Saadaoui ◽  
Francis Corson ◽  
Didier Rocancourt ◽  
Julian Roussel ◽  
Jerome Gros
Keyword(s):  
Large Scale ◽  
Stokes Equations ◽  
Primitive Streak ◽  
Self Organization ◽  
Mesoscopic Scale ◽  
Avian Embryos ◽  
Hydrodynamic Approach ◽  
Main Driver ◽  
Tissue Motion ◽  
Embryonic Disk

AbstractTissue morphogenesis is driven by local cellular deformations, themselves powered by contractile actomyosin networks. While it is well demonstrated that cell-generated forces at the microscopic scale underlie a variety of local morphogenetic processes (e.g. lengthening/ narrowing1–4, bending5–8, or folding9,10), how such local forces are transmitted across tissues to shape them at a mesoscopic scale remains largely unknown. Here, by performing a quantitative analysis of gastrulation in entire avian embryos, we show that the formation of the primitive streak and the associated large-scale rotational tissue flows (i.e. ‘polonaise’ movements11,12) are integral parts of a global process that is captured by the laws of fluid mechanics. We identify a large-scale supracellular actomyosin ring (2 mm in diameter and 250 μm thick) that shapes the embryo by exerting a graded tension along the margin between the embryonic and extra-embryonic territories. Tissue-wide flows arise from the transmission of these localized forces across the embryonic disk and are quantitatively recapitulated by a fluid-mechanical model based on the Stokes equations for viscous flow. We further show that cell division, the main driver of cell rearrangements at this stage13, is required for fluid-like behavior and for the progress of gastrulation movements. Our results demonstrate the power of a hydrodynamic approach to tissue-wide morphogenetic processes14–16 and provide a simple, unified mechanical picture of amniote gastrulation. A tensile embryo margin, in addition to directing tissue motion, could act as an interface between mechanical and molecular cues, and play a central role in embryonic self-organization.

Mixing of Matter by a Rising Bubble Near a Wall

2011 ◽  
Author(s):  
Toru Koso ◽  
Hiroyuki Iwashita ◽  
Fumihiko Usuki
Keyword(s):  
Large Scale ◽  
Uv Light ◽  
Fluid Motion ◽  
Turbulent Diffusion Coefficient ◽  
Air Bubble ◽  
Rising Bubble ◽  
Mass Dispersion ◽  
Mixing Patterns ◽  
Bubble Rising ◽  
Near Wall

The turbulent mixing of liquid mass caused by an air bubble rising near a wall in a still liquid in a pipe is investigated experimentally using a photochromic dye. A part of the liquid is activated by UV light and subjected to the fluid motion caused by a zigzag rising bubble of which Reynolds number is 214. The visualized mixing patterns showed that the dye is mixed by vortex motions in the bubble wake that is similar to the case of a bubble rising in the center of the pipe. The concentration distributions were deduced from the dye images using Lambert-Beer’s law and the turbulent diffusion coefficient (TDC) was evaluated from the temporal changes in the mass dispersion. The TDCs showed that a near-wall bubble generates stronger mixing than for a bubble in the center of the pipe. This stronger mixing can be attributed to the large-scale vortices observed for a near-wall bubble, which remains active for a longer time due to the lack of oppositely rotating vortices and mixes more fluids.

Genetic analysis of pattern formation in the Arabidopsis embryo

Development ◽  
1991 ◽  
Vol 113 (Supplement_1) ◽  
pp. 27-38 ◽  
Author(s):  
Gerd Jürgens ◽  
Ulrike Mayer ◽  
Torres Ruiz Ramon A. ◽  
Thomas Berleth ◽  
Simon Miséra
Keyword(s):  
Pattern Formation ◽  
Large Scale ◽  
Early Embryo ◽  
Flowering Plant ◽  
Abnormal Development ◽  
Mutant Seedling ◽  
Basic Body ◽  
Plant Embryo ◽  
Embryonic Pattern Formation ◽  
Plant Arabidopsis Thaliana

Virtually nothing is known about the mechanisms that generate the basic body pattern in plant embryogenesis. As a first step towards the analysis of pattern formation, we have isolated and begun to characterise putative pattern mutants in the flowering plant, Arabidopsis thaliana. A large-scale screen for morphologically abnormal seedling mutants yielded about 250 lines for further study, and genetic evidence suggests saturation of the genome for this kind of mutation. The phenotypes of putative pattern mutants fall into distinct categories, classes and groups, which may reflect specific aspects of embryonic pattern formation. Mutant seedling phenotypes result from abnormal development in the early embryo. The implications of our findings are discussed with regard to the prospects for a mechanistic understanding of pattern formation in the plant embryo.

scholarly journals Prediction and control of symmetry breaking in embryoid bodies by environment and signal integration

2018 ◽  
Author(s):  
Naor Sagy ◽  
Shaked Slovin ◽  
Maya Allalouf ◽  
Maayan Pour ◽  
Gaya Savyon ◽  
...  
Keyword(s):  
Symmetry Breaking ◽  
Cell Fate ◽  
Developmental Process ◽  
Primitive Streak ◽  
Early Embryo ◽  
Embryoid Bodies ◽  
Neighboring Cell ◽  
Contact Points

AbstractDuring early embryogenesis, mechanical signals, localized biochemical signals and neighboring cell layers interaction coordinate around anteroposterior axis determination and symmetry breaking. Deciphering their relative roles, which are hard to tease apart in vivo, will enhance our understanding of how these processes are driven. In recent years, in vitro 3D models of early mammalian development, such as embryoid bodies (EBs) and gastruloids, were successful in mimicking various aspects of the early embryo, providing high throughput accessible systems for studying the basic rules shaping cell fate and morphology during embryogenesis. Using Brachyury (Bry), a primitive streak and mesendoderm marker in EBs, we study how contact, biochemical and neighboring cell cues affect the positioning of a primitive streak-like locus, determining the AP axis. We show that a Bry-competent layer must be formed in the EB before Bry expression initiates, and that Bry onset locus selection depends on contact points of the EB with its surrounding. We can maneuver Bry onset to occur at a specific locus, a few loci, or in an isotropic peripheral pattern. By spatially separating contact and biochemical signal sources, we show these two modalities can be integrated by the EB to generate a single Bry locus. Finally, we show Foxa2+ cells are predictive of the future location of Bry onset, demonstrating an earlier symmetry-breaking event. By delineating the temporal signaling pathway dependencies of Bry and Foxa2, we were able to selectively abolish either, or spatially decouple the two cell types during EB differentiation. These findings demonstrate multiple inputs integration during an early developmental process, and may prove valuable in directing in vitro differentiation.

scholarly journals Proteomics and metabolomics in cow fertility: a systematic review

Reproduction ◽  
2020 ◽  
Vol 160 (5) ◽  
pp. 639-658
Author(s):  
Nicolas Aranciaga ◽  
James D Morton ◽  
Debra K Berg ◽  
Jessica L Gathercole
Keyword(s):  
Oxidative Stress ◽  
Systematic Review ◽  
Large Scale ◽  
Reproductive Tract ◽  
Early Embryo ◽  
Female Reproductive Tract ◽  
Full Potential ◽  
Technical Standards ◽  
The Impact

Cow subfertility is a multi-factorial problem in many countries which is only starting to be unravelled. Molecular biology can provide a substantial source of insight into its causes and potential solutions, particularly through large scale, untargeted omics approaches. In this systematic review, we set out to compile, assess and integrate the latest proteomic and metabolomic research on cow reproduction, specifically that on the female reproductive tract and early embryo. We herein report a general improvement in technical standards throughout the temporal span examined; however, significant methodological limitations are also identified. We propose easily actionable avenues for ameliorating these shortcomings and enhancing the reach of this field. Text mining and pathway analysis corroborate the relevance of proteins and metabolites related to the triad oxidative stress-inflammation-disease on reproductive function. We envisage a breakthrough in cattle reproductive molecular research within the next few years as in vivo sample techniques are improved, omics analysis equipment becomes more affordable and widespread, and software tools for single- and multi-omics data processing are further developed. Additional investigation of the impact of local oxidative stress and inflammation on fertility, both at the local and systemic levels, is key towards realising the full potential of this field.

The spatial and temporal distribution of polarizing activity in the flank of the pre-limb-bud stages in the chick embryo

Development ◽  
1991 ◽  
Vol 111 (3) ◽  
pp. 725-731 ◽  
Author(s):  
A. Hornbruch ◽  
L. Wolpert
Keyword(s):  
Posterior Part ◽  
Temporal Distribution ◽  
Early Embryo ◽  
Limb Bud ◽  
Posterior Edge ◽  
Limb Buds ◽  
Avian Embryos ◽  
Low Levels ◽  
Clear Change ◽  
Somitic Mesoderm

The presence of polarizing activity in the limb buds of developing avian embryos determines the pattern of the anteroposterior axis of the limbs in the adult. Maps of the spatial distribution and the strength of the signal within limb buds of different stages are well documented. Polarizing activity can also be found in Hensen's node in the early embryo. We have mapped the distribution of polarizing activity as it emerges from Hensen's node and spreads into the flank tissue of the embryo. There is a clear change in the local pattern of expression of polarizing activity between stage 8 and 18. Almost no activity is measured for stages 8 and 9. More or less uniform levels of around 10% are spread along the flank lateral to the unsegmented somitic mesoderm from somite position 12 to 22 in stage 10 embryos. Some 6 to 8 h later at stage 12, there is a distinct peak of activity at somite position 18, the middle of the wing field. This peak increases at stages 13 to 15 and its position traverses to the posterior edge of the wing field. Full strength of activity is reached shortly before the onset of limb bud formation at stage 16 to 17. Stages 16 to 18 were investigated for polarizing activity in the wing and the leg field. Low levels of polarizing activity are present in the anterior leg field at stages 16 and 17 but have disappeared by stage 18 and all activity is confined to the posterior part of the leg bud.

De novo induction of the organizer and formation of the primitive streak in an experimental model of notochord reconstitution in avian embryos

Development ◽  
1998 ◽  
Vol 125 (2) ◽  
pp. 201-213 ◽  
Author(s):  
S. Yuan ◽  
G.C. Schoenwolf
Keyword(s):  
Cell Fate ◽  
De Novo ◽  
Primitive Streak ◽  
Model System ◽  
Floor Plate ◽  
Avian Embryos ◽  
New Information ◽  
Derivatives Of ◽  
Novel Model ◽  
Neurula Stage

We have developed a model system for analyzing reconstitution of the notochord using cultured blastoderm isolates lacking Hensen's node and the primitive streak. Despite lacking normal notochordal precursor cells, the notochord still forms in these isolates during the 36 hours in culture. Reconstitution of the notochord involves an inducer, which acts upon a responder, thereby inducing a reconstituted notochord. To better understand the mechanism of notochord reconstitution, we asked whether formation of the notochord in the model system was preceded by reconstitution of Hensen's node, the organizer of the avian neuraxis. Our results show not only that a functional organizer is reconstituted, but that this organizer is induced from the responder. First, fate mapping reveals that the responder forms a density, morphologically similar to Hensen's node, during the first 10–12 hours in culture, and that this density expresses typical markers of Hensen's node. Second, the density, when fate mapped or when labeled and transplanted in place of Hensen's node, forms typical derivatives of Hensen's node such as endoderm, notochord and the floor plate of the neural tube. Third, the density, when transplanted to an ectopic site, induces a secondary neuraxis, identical to that induced by Hensen's node. And fourth, the density acts as a suppressor of notochord reconstitution, as does Hensen's node, when transplanted to other blastoderm isolates. Our results also reveal that the medial edge of the isolate forms a reconstituted primitive streak, which gives rise to the normal derivatives of the definitive primitive streak along its rostrocaudal extent and which expresses typical streak markers. Finally, our results demonstrate that the notochordal inducer also induces the reconstituted Hensen's node and, therefore, acts like a Nieuwkoop Center. These findings increase our understanding of the mechanism of notochord reconstitution, provide new information and a novel model system for studying the induction of the organizer and reveal the potential of the epiblast to regulate its cell fate and patterns of gene expression during late gastrula/early neurula stage in higher vertebrates.

scholarly journals Large-Scale Comparative Analysis Reveals A Simple Model To Predict The Prevalence Of Thyroid Nodules

2019 ◽  
Vol Volume 12 ◽  
pp. 225-232 ◽  
Author(s):  
Li Genpeng ◽  
Wang Lijuan ◽  
Lei Jianyong ◽  
Song Linlin ◽  
Tang Huairong ◽  
...  
Keyword(s):  
Comparative Analysis ◽  
Simple Model ◽  
Large Scale ◽  
Thyroid Nodules

Heat Transfer Enhancement of a Backward-Facing Step Flow in a Duct by Static and Dynamic Devices

2007 ◽  
Author(s):  
Kyoji Inaoka ◽  
Kouji Kawakami ◽  
Yoshi Nishii ◽  
Mamoru Senda
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Enhancement ◽  
Large Scale ◽  
Fluid Motion ◽  
Side Wall ◽  
Transfer Enhancement ◽  
Backward Facing Step ◽  
Electromagnetic Actuators ◽  
Flow Recirculation ◽  
Flow Modification

Flow modification downstream of a backward-facing step has been tried in order to achieve heat transfer enhancement by introducing two kinds of devices, a triangle prism rib and electromagnetic actuators, on the step edge. The triangle rib attached to the side-wall corner makes the downward flow inclined and generates a circulation-like fluid motion behind it. Because both flows work effective in reducing the flow re-circulation caused behind the step, large heat transfer recovery is obtained near the side-wall. This advantage of the triangle rib remains effective when the flap actuations are imposed. Thus, the large-scale unsteady vortex intensively reduces the flow recirculation, the triangle rib with flap actuations attains the largest heat transfer recovery behind the step.

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