scholarly journals Rab5-mediated Yolk Cell Endocytosis modulates Zebrafish Epiboly Biomechanics and Tissue Movements

2016 ◽  
Author(s):  
Maria Marsal ◽  
Amayra Hernández-Vega ◽  
Philippe-Alexandre Pouille ◽  
Enrique Martin-Blanco
Keyword(s):  
Tissue Mechanics ◽  
Force Balance ◽  
Zebrafish Embryos ◽  
Membrane Remodeling ◽  
Mechanical Tension ◽  
Morphogenetic Movements ◽  
Yolk Cell ◽  
Final Destination ◽  
Actomyosin Contractility ◽  
Spatio Temporal

SummaryMorphogenetic processes demand the coordinated allocation of cells and tissues to their final destination in a spatio-temporal controlled way. Identifying how these morphogenetic movements are directed and implemented is essential for understanding morphogenesis. Topographical and scalar differences in adhesion and contractility within and between cells are essential, yet, the role that membrane remodeling may play remains less clear. To clarify how surface turnover and dynamics may modulate tissue arrangements we studied epiboly in the zebrafish. During epiboly the blastoderm expands as a result of an asymmetry of mechanical tension along the embryo surface. In this scenario, we found that the membrane removal by macropinocytosis of the external yolk cell syncytial layer (E-YSL) ahead of the blastoderm is key for epiboly progression In early zebrafish embryos, the activity of the GTPase Rab5ab was essential for endocytosis, and interference in its expression exclusively in the yolk cell resulted in the reduction of yolk cell actomyosin contractility, the disruption of cortical and internal yolk flows, a disequilibrium in force balance and as a result epiboly impairment. We conclude that regulated membrane remodeling is crucial for directing cell and tissue mechanics and coordinating morphogenetic movements during epiboly.

scholarly journals Rab5ab-Mediated Yolk Cell Membrane Endocytosis Is Essential for Zebrafish Epiboly and Mechanical Equilibrium During Gastrulation

2021 ◽  
Vol 9 ◽  
Author(s):  
Maria Marsal ◽  
Amayra Hernández-Vega ◽  
Philippe-Alexandre Pouille ◽  
Enrique Martin-Blanco
Keyword(s):  
Tissue Mechanics ◽  
Force Balance ◽  
Membrane Remodeling ◽  
Internal Flows ◽  
Membrane Turnover ◽  
Morphogenetic Movements ◽  
Yolk Cell ◽  
Final Destination ◽  
Early Embryos ◽  
Spatio Temporal

Morphogenesis in early embryos demands the coordinated distribution of cells and tissues to their final destination in a spatio-temporal controlled way. Spatial and scalar differences in adhesion and contractility are essential for these morphogenetic movements, while the role that membrane remodeling may play remains less clear. To evaluate how membrane turnover modulates tissue arrangements we studied the role of endocytosis in zebrafish epiboly. Experimental analyses and modeling have shown that the expansion of the blastoderm relies on an asymmetry of mechanical tension in the yolk cell generated as a result of actomyosin-dependent contraction and membrane removal. Here we show that the GTPase Rab5ab is essential for the endocytosis and the removal of the external yolk cell syncytial layer (E-YSL) membrane. Interfering in its expression exclusively in the yolk resulted in the reduction of yolk cell actomyosin contractility, the disruption of cortical and internal flows, a disequilibrium in force balance and epiboly impairment. We conclude that regulated membrane remodeling is crucial for directing cell and tissue mechanics, preserving embryo geometry and coordinating morphogenetic movements during epiboly.

scholarly journals Optogenetic relaxation of actomyosin contractility uncovers mechanistic roles of cortical tension during cytokinesis

2021 ◽  
Author(s):  
Kei Yamamoto ◽  
Haruko Miura ◽  
Motohiko Ishida ◽  
Satoshi Sawai ◽  
Yohei Kondo ◽  
...  
Keyword(s):  
Traction Force ◽  
Tissue Mechanics ◽  
Light Illumination ◽  
Type I ◽  
Contractile Ring ◽  
Cortical Tension ◽  
Regulatory Light Chains ◽  
Actomyosin Contractility ◽  
Nonmuscle Myosin Ii ◽  
Wide Range

Actomyosin contractility generated cooperatively by nonmuscle myosin II and actin filaments plays essential roles in a wide range of biological processes, such as cell motility, cytokinesis, and tissue morphogenesis. However, it is still unknown how actomyosin contractility generates force and maintains cellular morphology. Here, we demonstrate an optogenetic method to induce relaxation of actomyosin contractility. The system, named OptoMYPT, combines a catalytic subunit of the type I phosphatase-binding domain of MYPT1 with an optogenetic dimerizer, so that it allows light-dependent recruitment of endogenous PP1c to the plasma membrane. Blue-light illumination was sufficient to induce dephosphorylation of myosin regulatory light chains and decrease in traction force at the subcellular level. The OptoMYPT system was further employed to understand the mechanics of actomyosin-based cortical tension and contractile ring tension during cytokinesis. We found that the relaxation of cortical tension at both poles by OptoMYPT accelerated the furrow ingression rate, revealing that the cortical tension substantially antagonizes constriction of the cleavage furrow. Based on these results, the OptoMYPT system will provide new opportunities to understand cellular and tissue mechanics.

scholarly journals Visualization of Mitochondrial Ca2+ Signals in Skeletal Muscle of Zebrafish Embryos with Bioluminescent Indicators

2019 ◽  
Vol 20 (21) ◽  
pp. 5409 ◽  
Author(s):  
Manuel Vicente ◽  
Jussep Salgado-Almario ◽  
Joaquim Soriano ◽  
Miguel Burgos ◽  
Beatriz Domingo ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Muscle Contractions ◽  
Zebrafish Embryos ◽  
Mitochondrial Matrix ◽  
Mitochondrial Calcium Uniporter ◽  
Calcium Uniporter ◽  
Skeletal Muscle Contraction ◽  
Spatio Temporal ◽  
Mitochondrial Uncoupler

Mitochondria are believed to play an important role in shaping the intracellular Ca2+ transients during skeletal muscle contraction. There is discussion about whether mitochondrial matrix Ca2+ dynamics always mirror the cytoplasmic changes and whether this happens in vivo in whole organisms. In this study, we characterized cytosolic and mitochondrial Ca2+ signals during spontaneous skeletal muscle contractions in zebrafish embryos expressing bioluminescent GFP-aequorin (GA, cytoplasm) and mitoGFP-aequorin (mitoGA, trapped in the mitochondrial matrix). The Ca2+ transients measured with GA and mitoGA reflected contractions of the trunk observed by transmitted light. The mitochondrial uncoupler FCCP and the inhibitor of the mitochondrial calcium uniporter (MCU), DS16570511, abolished mitochondrial Ca2+ transients whereas they increased the frequency of cytosolic Ca2+ transients and muscle contractions, confirming the subcellular localization of mitoGA. Mitochondrial Ca2+ dynamics were also determined with mitoGA and were found to follow closely cytoplasmic changes, with a slower decay. Cytoplasmic Ca2+ kinetics and propagation along the trunk and tail were characterized with GA and with the genetically encoded fluorescent Ca2+ indicator, Twitch-4. Although fluorescence provided a better spatio-temporal resolution, GA was able to resolve the same kinetic parameters while allowing continuous measurements for hours.

Recruitment and SNARE-mediated fusion of vesicles in furrow membrane remodeling during cytokinesis in zebrafish embryos

2006 ◽  
Vol 312 (17) ◽  
pp. 3260-3275 ◽  
Author(s):  
Wai Ming Li ◽  
Sarah E. Webb ◽  
Karen W. Lee ◽  
Andrew L. Miller
Keyword(s):  
Zebrafish Embryos ◽  
Membrane Remodeling

scholarly journals Simultaneous in vivo time-lapse stiffness mapping and fluorescence imaging of developing tissue

2018 ◽  
Author(s):  
Amelia J. Thompson ◽  
Iva K. Pillai ◽  
Ivan B. Dimov ◽  
Christine E. Holt ◽  
Kristian Franze
Keyword(s):  
Fluorescence Imaging ◽  
Temporal Dynamics ◽  
Time Lapse ◽  
Tissue Mechanics ◽  
Tissue Stiffness ◽  
Time Resolved ◽  
Force Microscopy ◽  
Atomic Force ◽  
Spatio Temporal

AbstractTissue mechanics is important for development; however, the spatio-temporal dynamics of in vivo tissue stiffness is still poorly understood. We here developed tiv-AFM, combining time-lapse in vivo atomic force microscopy with upright fluorescence imaging of embryonic tissue, to show that in the developing Xenopus brain, a stiffness gradient evolves over time because of differential cell proliferation. Subsequently, axons turn to follow this gradient, underpinning the importance of time-resolved mechanics measurements.

scholarly journals Coronin 1A depletion restores the nuclear stability and viability of Aip1/Wdr1-deficient neutrophils

2019 ◽  
Vol 218 (10) ◽  
pp. 3258-3271
Author(s):  
Charnese Bowes ◽  
Michael Redd ◽  
Malika Yousfi ◽  
Muriel Tauzin ◽  
Emi Murayama ◽  
...  
Keyword(s):  
Cell Death ◽  
Actin Filaments ◽  
Essential Role ◽  
Actin Dynamics ◽  
Actin Binding ◽  
Zebrafish Embryos ◽  
Actomyosin Contractility ◽  
Nuclear Stability

Actin dynamics is central for cells, and especially for the fast-moving leukocytes. The severing of actin filaments is mainly achieved by cofilin, assisted by Aip1/Wdr1 and coronins. We found that in Wdr1-deficient zebrafish embryos, neutrophils display F-actin cytoplasmic aggregates and a complete spatial uncoupling of phospho-myosin from F-actin. They then undergo an unprecedented gradual disorganization of their nucleus followed by eruptive cell death. Their cofilin is mostly unphosphorylated and associated with F-actin, thus likely outcompeting myosin for F-actin binding. Myosin inhibition reproduces in WT embryos the nuclear instability and eruptive death of neutrophils seen in Wdr1-deficient embryos. Strikingly, depletion of the main coronin of leukocytes, coronin 1A, fully restores the cortical location of F-actin, nuclear integrity, viability, and mobility of Wdr1-deficient neutrophils in vivo. Our study points to an essential role of actomyosin contractility in maintaining the integrity of the nucleus of neutrophils and a new twist in the interplay of cofilin, Wdr1, and coronin in regulating F-actin dynamics.

scholarly journals Cell tension and mechanical regulation of cell volume

2018 ◽  
Vol 29 (21) ◽  
pp. 0-0 ◽  
Author(s):  
Nicolas Perez Gonzalez ◽  
Jiaxiang Tao ◽  
Nash D. Rochman ◽  
Dhruv Vig ◽  
Evelyn Chiu ◽  
...  
Keyword(s):  
Cell Volume ◽  
Force Balance ◽  
Cell Cortex ◽  
Animal Cells ◽  
Mechanical Tension ◽  
Average Cell ◽  
Physical Size ◽  
Average Cell Volume ◽  
Cell Growth And Proliferation ◽  
Exclusion Method

Animal cells use an unknown mechanism to control their growth and physical size. Here, using the fluorescence exclusion method, we measure cell volume for adherent cells on substrates of varying stiffness. We discover that the cell volume has a complex dependence on substrate stiffness and is positively correlated with the size of the cell adhesion to the substrate. From a mechanical force–balance condition that determines the geometry of the cell surface, we find that the observed cell volume variation can be predicted quantitatively from the distribution of active myosin through the cell cortex. To connect cell mechanical tension with cell size homeostasis, we quantified the nuclear localization of YAP/TAZ, a transcription factor involved in cell growth and proliferation. We find that the level of nuclear YAP/TAZ is positively correlated with the average cell volume. Moreover, the level of nuclear YAP/TAZ is also connected to cell tension, as measured by the amount of phosphorylated myosin. Cells with greater apical tension tend to have higher levels of nuclear YAP/TAZ and a larger cell volume. These results point to a size-sensing mechanism based on mechanical tension: the cell tension increases as the cell grows, and increasing tension feeds back biochemically to growth and proliferation control.

scholarly journals Fibronectin-dependent tissue mechanics regulate the translation of segmentation clock oscillations into periodic somite formation

2019 ◽  
Author(s):  
Patrícia Gomes de Almeida ◽  
Pedro Rifes ◽  
Ana Patrícia Martins-Jesus ◽  
Gonçalo G. Pinheiro ◽  
Raquel P. Andrade ◽  
...  
Keyword(s):  
Gene Expression ◽  
Clock Gene ◽  
Clock Genes ◽  
Tissue Mechanics ◽  
Matrix Assembly ◽  
Segmentation Clock ◽  
Clock Gene Expression ◽  
Fibronectin Matrix ◽  
Somite Formation ◽  
Spatio Temporal

AbstractSomitogenesis starts with cyclic waves of expression of segmentation clock genes in the presomitic mesoderm (PSM) and culminates with periodic budding of somites in its anterior-most region. How cyclic clock gene expression is translated into timely morphological somite formation has remained unclear. A posterior to anterior gradient of increasing PSM tissue cohesion correlates with increasing fibronectin matrix complexity around the PSM, suggesting that fibronectin-dependent tissue mechanics may be involved in this transition. Here we address whether the mechanical properties of the PSM tissue play a role in regulating the pathway leading to cleft formation in the anterior PSM. We first interfered with cytoskeletal contractility in the chick PSM by disrupting actomyosin-mediated contractility directly or via Rho-associated protein kinase function. Then we perturbed fibronectin matrix accumulation around the PSM tissue by blocking integrin-fibronectin binding or fibronectin matrix assembly. All four treatments perturbed hairy1 and meso1 expression dynamics and resulted in defective somitic clefts. A model is presented where a gradient of fibronectin-dependent tissue mechanics participates in the PSM wavefront of maturation by ensuring the correct spatio-temporal conversion of cyclic segmentation clock gene expression into periodic somite formation.

scholarly journals Network architecture determines vein fate during spontaneous reorganization, with a time delay

2021 ◽  
Author(s):  
Sophie Marbach ◽  
Noah Ziethen ◽  
Leonie Bastin ◽  
Felix Baeuerle ◽  
Karen Alim
Keyword(s):  
Time Delay ◽  
Network Architecture ◽  
Force Balance ◽  
Relative Pressure ◽  
Temporal Data ◽  
Vascular Networks ◽  
Local Shear ◽  
Flow Shear Stress ◽  
Spatio Temporal

Vascular networks continuously reorganize their morphology by growing new or shrinking existing veins to optimize function. Flow shear stress on vein walls has been set forth as the local driver for this continuous adaptation. Yet, shear feedback alone cannot account for the observed diversity of network dynamics -- a puzzle made harder by scarce spatio-temporal data. Here, we resolve network-wide vein dynamics and shear during spontaneous reorganization in the prototypical vascular networks of Physarum polycephalum. Our experiments reveal a plethora of vein dynamics (stable, growing, shrinking) that are not directly proportional to local shear. We observe (a) that shear rate sensing on vein walls occurs with a time delay of 1 to 3 min and (b) that network architecture dependent parameters -- such as relative pressure or relative vein resistance -- are key to determine vein fate. We derive a model for vascular adaptation, based on force balance at the vein walls. Together with the time delay, our model reproduces the diversity of experimentally observed vein dynamics, and confirms the role of network architecture. Finally, we observe avalanches of network reorganization events which cause entire clusters of veins to vanish. Such avalanches are consistent with architectural feedback as the vein connections perpetually change with reorganization. As these network architecture dependent parameters are intrinsically connected with the laminar fluid flow in the veins, we expect our findings to play a role across flow-based vascular networks.

scholarly journals Mechanical Forces during Lymph Node Expansion Govern Fibroblastic Reticular Network Remodeling

2021 ◽  
Author(s):  
Harry L Horsnell ◽  
Robert J Tetley ◽  
Henry de Belly ◽  
Spiros Makris ◽  
Agnesska C Benjamin ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Lymph Node ◽  
Adaptive Immune Response ◽  
Tissue Mechanics ◽  
Mechanical Forces ◽  
Cortical Tension ◽  
Lectin Receptor ◽  
Actomyosin Contractility ◽  
The Impact ◽  
Fibroblastic Stroma

After immunogenic challenge, the lymph node rapidly increases in cellularity making space for infiltrating and dividing lymphocytes, expanding the tissue. In the early phases of expansion, the underlying fibroblastic stroma, which organises the lymph node, undergoes elongation and stretching. This is followed by the initiation of fibroblastic stroma proliferation as inflammation proceeds. In the steady state, fibroblastic reticular cells (FRCs) tightly wrap an interconnected network of extracellular matrix fibres. The initial physical deformability of the lymph node is in part determined by Podoplanin (PDPN) signalling in FRCs and is modulated by dendritic cells expressing C-type lectin receptor 2 (CLEC-2). However, the mechanisms changing tissue and cellular mechanical forces of the fibroblastic stroma and the triggers for FRC proliferation and growth are unknown. We examined the contributions of FRC actomyosin contractility and extracellular matrix to lymph node tissue tension. Further, we directly tested the impact of tissue mechanics on the kinetics of lymph node expansion. We show using laser ablation that the FRC network is under mechanical tension generated by actomyosin contractility and that tension changes throughout the course of immunogenic challenge. We find that CLEC-2/PDPN signalling alters the cell intrinsic mechanical state of FRCs by reducing cortical tension and increasing FRC size. We found that FRC network tension is a critical cue in controlling lymph node expansion gating the initiation of FRC proliferation. Together this study demonstrates mechanical forces are generated and sensed through the FRC network to determine lymph node expansion required for an adaptive immune response.

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