Mechanical bistability enabled by ectodermal compression facilitates Drosophila mesoderm invagination

Apical constriction driven by non-muscle myosin II (″myosin″) provides a well-conserved mechanism to mediate epithelial folding. It remains unclear how contractile forces near the apical surface of a cell sheet drive out-of-plane bending of the sheet and whether myosin contractility is required throughout folding. By optogenetic-mediated acute inhibition of myosin, we find that during Drosophila mesoderm invagination, myosin contractility is critical to prevent tissue relaxation during the early, ″priming″ stage of folding but is dispensable for the actual folding step after the tissue passes through a stereotyped transitional configuration, suggesting that the mesoderm is mechanically bistable during gastrulation. Combining computer modeling and experimental measurements, we show that the observed mechanical bistability arises from an in-plane compression from the surrounding ectoderm, which promotes mesoderm invagination by facilitating a buckling transition. Our results indicate that Drosophila mesoderm invagination requires a joint action of local apical constriction and global in-plane compression to trigger epithelial buckling.

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Mechanical competition alters the cellular interpretation of an endogenous genetic program

The Journal of Cell Biology ◽

10.1083/jcb.202104107 ◽

2021 ◽

Vol 220 (11) ◽

Author(s):

Sourabh Bhide ◽

Denisa Gombalova ◽

Gregor Mönke ◽

Johannes Stegmaier ◽

Valentyna Zinchenko ◽

...

Keyword(s):

Genetic Program ◽

Cell Behavior ◽

Mechanical Stimuli ◽

Apical Constriction ◽

Actin Reorganization ◽

Ductile Materials ◽

Nonlinear Mechanical ◽

A Cell ◽

Contractile Forces ◽

Strain Responses

The intrinsic genetic program of a cell is not sufficient to explain all of the cell’s activities. External mechanical stimuli are increasingly recognized as determinants of cell behavior. In the epithelial folding event that constitutes the beginning of gastrulation in Drosophila, the genetic program of the future mesoderm leads to the establishment of a contractile actomyosin network that triggers apical constriction of cells and thereby tissue folding. However, some cells do not constrict but instead stretch, even though they share the same genetic program as their constricting neighbors. We show here that tissue-wide interactions force these cells to expand even when an otherwise sufficient amount of apical, active actomyosin is present. Models based on contractile forces and linear stress–strain responses do not reproduce experimental observations, but simulations in which cells behave as ductile materials with nonlinear mechanical properties do. Our models show that this behavior is a general emergent property of actomyosin networks in a supracellular context, in accordance with our experimental observations of actin reorganization within stretching cells.

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LMO7-dependent apical constriction requires the binding of the Myosin heavy chain

10.1101/2021.05.12.443820 ◽

2021 ◽

Author(s):

Miho Matsuda ◽

Chih-Wen Chu ◽

Sergei S Sokol

Keyword(s):

Heavy Chain ◽

Myosin Light Chain ◽

Myosin Ii ◽

Tube Formation ◽

Epithelial Morphogenesis ◽

Apical Constriction ◽

Actomyosin Contractility ◽

Apical Domain ◽

Underlying Mechanisms ◽

Muscle Myosin

The reduction of the apical domain, or apical constriction, is a process that occurs in a single cell or is coordinated in a group of cells in the epithelium. Coordinated apical constriction is particularly important when the epithelium is undergoing dynamic morphogenetic events such as furrow or tube formation. However, the underlying mechanisms remain incompletely understood. Here we show that Lim only protein 7 (Lmo7) is a novel activator of apical constriction in the Xenopus superficial ectoderm, which coordinates actomyosin contractility in a group of cells during epithelial morphogenesis. Like other apical constriction regulators, Lmo7 requires the activation of the Rho-Rock-Myosin II pathway to induce apical constriction. However, instead of increasing the phosphorylation of myosin light chain (MLC), Lmo7 binds muscle myosin II heavy chain A (NMIIA) and increases its association with actomyosin bundles at adherens junctions (AJs). Lmo7 overexpression modulates the subcellular distribution of Wtip, a tension marker at AJs, suggesting that Lmo7 generates mechanical forces at AJs. We propose that Lmo7 increases actomyosin contractility at AJs by promoting the formation of actomyosin bundles.

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Cortical contraction drives the 3D patterning of epithelial cell surfaces

10.1101/819987 ◽

2019 ◽

Author(s):

Aaron P. van Loon ◽

Ivan S. Erofeev ◽

Ivan V. Maryshev ◽

Andrew B. Goryachev ◽

Alvaro Sagasti

Keyword(s):

Surface Tension ◽

Myosin Ii ◽

Biomechanical Model ◽

Cell Surfaces ◽

Apical Constriction ◽

Skin Cells ◽

In Vivo Experiments ◽

Surface Topographies ◽

Muscle Myosin

ABSTRACTCellular protrusions create complex cell surface topographies, but biomechanical mechanisms regulating their formation and arrangement are largely unknown. To study how protrusions form, we focused on the morphogenesis of microridges, elongated actin-based structures projecting from the apical surfaces of zebrafish skin cells that are arranged in labyrinthine patterns. Microridges form by accreting simple finger-like precursors. Live imaging demonstrated that microridge morphogenesis is linked to apical constriction. A non-muscle myosin II (NMII) reporter revealed pulsatile contractions of the actomyosin cortex; inhibiting NMII demonstrated that contractions are required for apical constriction and microridge formation. A biomechanical model suggested that contraction reduces surface tension to permit the fusion of precursors into microridges. Indeed, reducing surface tension with hyperosmolar media promoted microridge formation. In anisotropically stretched cells, microridges formed by precursor fusion along the stretch axis, which computational modeling explained as a consequence of stretch-induced cortical flow. Collectively, our results demonstrate how contraction within the 2D plane of the cortex patterns 3D cell surfaces.SUMMARYMicroridges, elongated 3D protrusions arranged in maze-like patterns on zebrafish skin cells, form by the accretion of simple precursor projections. Modeling and in vivo experiments showed that cortical contractions promote the coalescence of precursors into microridges by reducing membrane tension.

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Optogenetic control of apical constriction induces synthetic morphogenesis in mammalian tissues

10.1101/2021.04.20.440475 ◽

2021 ◽

Author(s):

Guillermo Martinez-Ara ◽

Nuria Taberner ◽

Mami Takayama ◽

Elissavet Sandaltzopoulou ◽

Casandra Edelweiss Villava ◽

...

Keyword(s):

Epithelial Cell ◽

Cell Sheet ◽

Three Dimensional ◽

Apical Surface ◽

Apical Constriction ◽

Mammalian Tissues ◽

Optic Vesicles ◽

Soft Gels ◽

Cellular Forces ◽

Spatiotemporal Control

During embryonic development, cellular forces synchronize in space and time to generate functional tissue shapes. Apical constriction is one of these force-generating processes, and it is necessary to modulate epithelial curvature in fundamental morphogenetic events, such as neural tube folding. The emerging field of synthetic developmental biology proposes bottom-up approaches to examine the contribution of each cellular process to complex morphogenesis. However, the shortage of tools to manipulate three-dimensional (3D) shapes of mammalian tissues currently hinders the progress of the field. Here we report the development of 'OptoShroom3', a new optogenetic tool that achieves fast spatiotemporal control of apical constriction in mammalian epithelia. Activation of OptoShroom3 through illumination of individual cells in an epithelial cell sheet reduced their apical surface while illumination of groups of cells caused deformation in the adjacent regions. By using OptoShroom3, we further manipulated 3D tissue shapes. Light-induced apical constriction provoked the folding of epithelial cell colonies on soft gels. Its application to murine and human neural organoids led to thickening of neuroepithelia, apical lumen reduction in optic vesicles, and flattening in neuroectodermal tissues. These results show that spatiotemporal control of apical constriction can trigger several types of 3D deformation depending on the initial tissue context.

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Real-time imaging of cell-cell adherens junctions reveals that Drosophila mesoderm invagination begins with two phases of apical constriction of cells

Journal of Cell Science ◽

10.1242/jcs.114.3.493 ◽

2001 ◽

Vol 114 (3) ◽

pp. 493-501 ◽

Cited By ~ 30

Author(s):

H. Oda ◽

S. Tsukita

Keyword(s):

Real Time ◽

Cell Shape ◽

Adherens Junctions ◽

Cell Sheet ◽

Apical Surface ◽

Apical Constriction ◽

Real Time Imaging ◽

Cell Shape Changes ◽

Shape Changes ◽

Cell Cell

Invagination of the epithelial cell sheet of the prospective mesoderm in Drosophila gastrulation is a well-studied, relatively simple morphogenetic event that results from dynamic cell shape changes and cell movements. However, these cell behaviors have not been followed at a sufficiently short time resolution. We examined mesoderm invagination in living wild-type embryos by real-time imaging of fluorescently labeled cell-cell adherens junctions, which are located at the apical zones of cell-cell contact. Low-light fluorescence video microscopy directly visualized the onset and progression of invagination. In an initial period of approximately 2 minutes, cells around the ventral midline reduced their apical surface areas slowly in a rather synchronous manner. Next, the central and more lateral cells stochastically accelerated or initiated their apical constriction, giving rise to random arrangements of cells with small and relatively large apices. Thus, we found that mesoderm invagination began with slow synchronous and subsequent fast stochastic phases of cell apex constriction. Furthermore, we showed that the mesoderm invagination of folded gastrulation mutant embryos lacked the normal two constriction phases, and instead began with asynchronous, feeble cell shape changes. Our observations suggested that Folded gastrulation-mediated signaling enabled synchronous activation of the contractile cortex, causing competition among the individual mesodermal cells for apical constriction. Movies available on-line: http://www.biologists.com/JCS/movies/jcs2073.html

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Non-muscle myosin II heavy chain has a cryptic cell-adhesion domain

Biochemical Journal ◽

10.1042/bj3090569 ◽

1995 ◽

Vol 309 (2) ◽

pp. 569-574 ◽

Cited By ~ 1

Author(s):

F Grinnell ◽

C H Ho

Keyword(s):

Cell Adhesion ◽

Sequence Analysis ◽

Heavy Chain ◽

Myosin Ii ◽

Cross Reactivity ◽

Bhk Cells ◽

A Cell ◽

The Cross ◽

Muscle Myosin

We have discovered a cryptic cell-adhesion domain in non-muscle myosin II heavy chain. A 205 kDa cell-adhesion-promoting polypeptide (p205) was extracted from BHK cells by Nonidet P-40 or Dounce homogenization. Adhesion to p205 was specifically inhibited by the peptide Gly-Arg-Gly-Asp-Ser-Pro, indicating a role for the Arg-Gly-Asp cell-adhesion motif. Purified p205 was identified as non-muscle myosin II heavy chain, based on sequence analysis and on the cross-reactivity of p205 with anti-(bovine trachea myosin) antibodies. Further experiments showed that the heavy chain of purified myosin II has cell-adhesion-promoting activity in a cell-blotting assay, and cross-reacted with anti-p205 antibodies. Finally, the adhesion domain was located in the tail portion of myosin II heavy chain, where an Arg-Gly-Asp-containing sequence can be found.

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Conventional and Non-Conventional Roles of Non-Muscle Myosin II-Actin in Neuronal Development and Degeneration

Cells ◽

10.3390/cells9091926 ◽

2020 ◽

Vol 9 (9) ◽

pp. 1926

Author(s):

Míriam Javier-Torrent ◽

Carlos A. Saura

Keyword(s):

Neuronal Development ◽

Myosin Ii ◽

Deep Understanding ◽

Cellular Mechanisms ◽

Cytoskeletal Dynamics ◽

And Migration ◽

Contractile Forces ◽

Muscle Myosin ◽

Actin Cytoskeletal Dynamics ◽

The Brain

Myosins are motor proteins that use chemical energy to produce mechanical forces driving actin cytoskeletal dynamics. In the brain, the conventional non-muscle myosin II (NMII) regulates actin filament cytoskeletal assembly and contractile forces during structural remodeling of axons and dendrites, contributing to morphology, polarization, and migration of neurons during brain development. NMII isoforms also participate in neurotransmission and synaptic plasticity by driving actin cytoskeletal dynamics during synaptic vesicle release and retrieval, and formation, maturation, and remodeling of dendritic spines. NMIIs are expressed differentially in cerebral non-neuronal cells, such as microglia, astrocytes, and endothelial cells, wherein they play key functions in inflammation, myelination, and repair. Besides major efforts to understand the physiological functions and regulatory mechanisms of NMIIs in the nervous system, their contributions to brain pathologies are still largely unclear. Nonetheless, genetic mutations or deregulation of NMII and its regulatory effectors are linked to autism, schizophrenia, intellectual disability, and neurodegeneration, indicating non-conventional roles of NMIIs in cellular mechanisms underlying neurodevelopmental and neurodegenerative disorders. Here, we summarize the emerging biological roles of NMIIs in the brain, and discuss how actomyosin signaling contributes to dysfunction of neurons and glial cells in the context of neurological disorders. This knowledge is relevant for a deep understanding of NMIIs on the pathogenesis and therapeutics of neuropsychiatric and neurodegenerative diseases.

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Gonococcal invasion into epithelial cells depends on both cell polarity and ezrin

10.1101/2021.04.29.441923 ◽

2021 ◽

Author(s):

Qian Yu ◽

Liang-Chun Wang ◽

Daniel C. Stein ◽

Wenxia Song

Keyword(s):

Epithelial Cells ◽

Immunofluorescence Microscopy ◽

Myosin Ii ◽

Epithelial Cell Line ◽

Apical Surface ◽

Cervical Tissue ◽

Symptomatic Infection ◽

Polarized Epithelial Cells ◽

Cervical Epithelial Cells ◽

Muscle Myosin

AbstractNeisseria gonorrhoeae (GC) establishes symptomatic infection in women from the cervix, lined with heterogeneous epithelial cells from non-polarized stratified at the ectocervix to polarized columnar at the endocervix. We have previously shown that GC differentially colonize and transmigrate across the ecto and endocervical epithelia. However, whether and how GC invade into heterogeneous cervical epithelial cells is unknown. This study examined GC entry of epithelial cells with various properties, using human cervical tissue explant and non-polarized/polarized epithelial cell line models. While adhering to non-polarized and polarized epithelial cells at similar levels, GC invaded into non-polarized more efficiently than polarized epithelial cells. The enhanced GC invasion in non-polarized epithelial cells was associated with increased ezrin phosphorylation, F-actin and ezrin recruitment to GC adherent sites, and the elongation of GC-associated microvilli. Inhibition of ezrin phosphorylation inhibited F-actin and ezrin recruitment and microvilli elongation, leading to a reduction in GC invasion. The reduced GC invasion in polarized epithelial cells was associated with non-muscle myosin II-mediated F-actin disassembly and microvilli ablation at GC adherence sites. Surprisingly, intraepithelial GC were only detected inside epithelial cells shed from the cervix, but neither in the ectocervix nor the endocervix, by immunofluorescence microscopy. We observed similar ezrin and F-actin recruitment in exfoliated cervical epithelial cells but not in those that remained in the ectocervical epithelium, as the luminal layer of ectocervical epithelial cells expressed ten-fold lower levels of ezrin than those beneath. However, GC inoculation induced F-actin reduction and myosin recruitment in the endocervix, similar to what was seen in polarized epithelial cells. Thus, polarized expression of ezrin at the apical surface of epithelial cells inhibits GC invasion, while non-polarized expression of ezrin promotes GC invasion by driving actin accumulation and microvilli elongation.

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Mechanical competition alters the cellular interpretation of an endogenous genetic programme

10.1101/2020.10.15.333963 ◽

2020 ◽

Author(s):

Sourabh Bhide ◽

Denisa Gombalova ◽

Gregor Mönke ◽

Johannes Stegmaier ◽

Valentyna Zinchenko ◽

...

Keyword(s):

Mechanical Properties ◽

Emergent Property ◽

Mechanical Stimuli ◽

Cell Behaviour ◽

Apical Constriction ◽

Ductile Materials ◽

A Cell ◽

Contractile Forces ◽

Strain Responses ◽

Genetic Programme

AbstractThe intrinsic genetic programme of a cell is not sufficient to explain all of the cell’s activities. External mechanical stimuli are increasingly recognized as determinants of cell behaviour. In the epithelial folding event that constitutes the beginning of gastrulation in Drosophila, the genetic programme of the future mesoderm leads to the establishment of a contractile actomyosin network that triggers apical constriction of cells, and thereby, tissue folding. However, some cells do not constrict but instead stretch, even though they share the same genetic programme as their constricting neighbours. We show here that tissue-wide interactions force these cells to expand even when an otherwise sufficient amount of apical, active actomyosin is present. Models based on contractile forces and linear stress-strain responses do not reproduce experimental observations, but simulations in which cells behave as ductile materials with non-linear mechanical properties do. Our models show that this behaviour is a general emergent property of actomyosin networks [in a supracellular context, in accordance with our experimental observations of actin reorganisation within stretching cells.

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Elimination Of Aberrantly Specified Cell Clones Is Independent Of Interfacial Myosin II Accumulation

10.1101/2021.05.14.444162 ◽

2021 ◽

Author(s):

Olga Klipa ◽

Fisun Hamaratoglu

Keyword(s):

Spatial Organization ◽

Myosin Ii ◽

Cell Types ◽

Wild Type ◽

Apical Constriction ◽

Cell Clones ◽

Distinct Cell ◽

Tensile Forces ◽

Muscle Myosin

Spatial organization of differently fated cells within an organ is essential and needs to be maintained during development. This is largely implemented via compartment boundaries that serve as barriers between distinct cell types. Biased accumulation of junctional non-muscle Myosin II along the interface between differently fated groups of cells contributes to boundary integrity and maintains its shape via increased tension. Here we test whether interfacial Myosin driven tension is responsible for the elimination of aberrantly specified cells that would otherwise compromise compartment organization. To this end, we genetically reduce Myosin II levels in three different patterns: in both wild-type and misspecified cells, only in misspecified cells and specifically at the interface between wild-type and aberrantly specified cells. We find that recognition and elimination of aberrantly specified cells do not rely on tensile forces driven by interfacial Myosin cables. Moreover, apical constriction of misspecified cells and their separation from wild type neighbors occurs even when Myosin level is greatly reduced. Thus, we conclude that the forces that drive elimination of aberrantly specified cells are largely independent of Myosin II.

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