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Eukaryotic cells depend on dynamic changes in shape to fulfill a wide range of cellular functions, maintain essential biological processes, and regulate cellular behavior. The single-celled, predatory ciliate Lacrymaria exhibits extraordinary dynamic shape-shifting using a flexible "neck" that can stretch 7–8 times the length of its body to capture prey. The molecular mechanism behind this morphological change remains a mystery. We have observed that when in an active state, Lacrymaria repeatedly extends and contracts its neck to enable 360-degree space search and prey capture. This remarkable morphological change involves a unique actin-myosin system rather than the Ca2+-dependent system found in other contractile ciliates. Two cytoskeletons are identified in the cortex of the Lacrymaria cell, namely the myoneme cytoskeleton and the microtubule cytoskeleton. The myoneme cytoskeleton is composed of centrin-myosin proteins, exhibiting distinct patterns between the neck and body, with their boundary seemingly associated with the position of the macronucleus. A novel giant protein forming a ladder-like structure was discovered as a component of the microtubule cytoskeleton. Thick centrin-myosin fibers are situated very close to the right side of the ladders in the neck but are far away from such structures in the body. This arrangement enables the decoupling of the neck and body. Plasmodium -like unconventional actin has been discovered in Lacrymaria , and this may form highly dynamic short filaments that could attach to the giant protein and myosin, facilitating coordination between the two cytoskeletons in the neck. In summary, this fascinating organism employs unconventional cytoskeletal components to accomplish its extraordinary dynamic shape-shifting. [Display omitted] • Lacrymaria uses a unique actin-myosin system for neck morphology changes • Two cytoskeletal structures with unconventional components work together • The centrin-myosin-based myoneme shows distinct patterns in neck and body • A giant protein forms a ladder structure in the microtubule cytoskeleton Qin et al. discover the mechanism behind the remarkable shape-shifting of the unicellular predator, Lacrymaria. They identify two key cytoskeletal structures: a centrin-myosin-based myoneme and a giant protein-containing microtubule cytoskeleton. These structures work together to decouple the neck and body, enabling its dynamic neck morphology. [ABSTRACT FROM AUTHOR]

Septate junctions (SJs) serve as occluding barriers in invertebrate epithelia. In Drosophila, at least 30 genes are required for the formation or maintenance of SJs. Interestingly, loss-of-function mutations in core SJ components are embryonic lethal, with defects in developmental events such as head involution and dorsal closure (DC) that occur prior to the formation of a mature SJ, indicating a role for these proteins in mid-embryogenesis independent of their occluding function. To understand this novel function in development, we examined loss-of-function mutations in three core SJ proteins during the process of DC. DC occurs during mid-embryogenesis to seal a dorsal gap in the epidermis following germ band retraction. Closure is driven by contraction of the extraembryonic amnioserosa cells that temporarily cover the dorsal surface and by cell shape changes (elongation) of lateral epidermal cells that bring the contralateral sheets together at the dorsal midline. Using live imaging and examination of fixed tissues, we show that early events in DC occur normally in SJ mutant embryos, but during later closure, coracle, Macroglobulin complement-related and Neurexin-IV mutant embryos exhibit slower rates of closure and display aberrant cells shapes in the dorsolateral epidermis, including dorsoventral length and apical surface area. SJ mutant embryos also show mild defects in actomyosin structures along the leading edge, but laser cutting experiments suggest similar tension and viscoelastic properties in SJ mutant versus wild type epidermis. In a high percentage of SJ mutant embryos, the epidermis tears free from the amnioserosa near the end of DC and live imaging and immunostaining reveal reduced levels of E-cadherin, suggesting that defective adhesion may be responsible for these tears. Supporting this notion, reducing E-cadherin by half significantly enhances the penetrance of DC defects in coracle mutant embryos.

Dorsal closure is a prominent morphogenetic process during Drosophila embryogenesis, which involves two epithelial tissues, that is, the squamous amnioserosa and the columnar lateral epidermis. Non-muscle myosin II-driven constriction in the amnioserosa leads to a decrease in the apical surface area and pulls on the adjacent lateral epidermis, which subsequently moves dorsally. The pull by the amnioserosa becomes obvious in an elongation of the epidermal cells, especially of those in the first row. The contribution of the epidermal cell elongation has remained unclear to dorsal closure. Cell elongation may be a mere passive consequence or an active response to the pulling by the amnioserosa. Here, we found that the lateral epidermis actively responds. We analyzed tensions within tissues and cell junctions by laser ablation before and during dorsal closure, the elliptical and dorsal closure stages, respectively. Furthermore, we genetically and optochemically induced chronic and acute cell contraction, respectively. In this way, we found that tension in the epidermis increased during dorsal closure. A correspondingly increased tension was not observed at individual junctions, however. Junctional tension even decreased during dorsal closure in the epidermis. We strikingly observed a strong increase of the microtubule amount in the epidermis, while non-muscle myosin II increased in both tissues. Our data suggest that the epidermis actively antagonizes the pull from the amnioserosa during dorsal closure and the increased microtubules might help the epidermis bear part of the mechanical force.

A simple machine is a basic of device that takes mechanical advantage to apply force. Animals and plants self-assemble through the operation of a wide variety of simple machines. Embryos of different species actuate these simple machines to drive the geometric transformations that convert a disordered mass of cells into organized structures with discrete identities and function. These transformations are intrinsically coupled to sequential and overlapping steps of self-organization and self-assembly. The processes of self-organization have been explored through the molecular composition of cells and tissues and their information networks. By contrast, efforts to understand the simple machines underlying self-assembly must integrate molecular composition with the physical principles of mechanics. This primer is concerned with effort to elucidate the operation of these machines, focusing on the "problem" of morphogenesis. Advances in understanding self-assembly will ultimately connect molecular-, subcellular-, cellular- and meso-scale functions of plants and animals and their ability to interact with larger ecologies and environmental influences., (Copyright © 2024. Published by Elsevier Inc.)

Abstract It has been proposed that Ca2+ activation of calpain-1 is an important trigger for rapid cell spreading by neutrophils. In this paper, we have investigated this by assessing the ex vivo functioning of neutrophils from calpain-1 null mice, Calpain-1 null neutrophils failed to migrate through TNF-activated endothelial monolayers. The failure to transmigrate through endothelial monolayers was therefore unlikely to be due to a failure of chemotaxis as chemotaxis by adherent calpain-1 null neutrophils towards fMLP was unpaired. In contrast, the capacity of calpian-1 neutrophils to spontaneously spread was limited to smaller diameters than for wild type cells. Photolytic uncaging of IP 3 with Individual wild type neutrophils resulted in a large Ca2+ signal and rapid cell spreading. In contrast, calpain-1 neutrophils failed to spread in response to the IP 3 -induced Ca2+ signal. This work has therefore demonstrated that the presence of calpain-1 was required for effective rapid cell spreading by neutrophils. Graphical abstract Image 1 Highlights • The role of calpain-1 in neutrophil shape change was investigated. • Neutrophils were obtained from knock-out mice and assessed ex vivo. • These cells failed to migrate through endothelial monolayers. • Spontaneous cell spreading was grossly abberant. • Calpain-1 null cells failed to spread in response to IP 3 -induced Ca2+ signals. [ABSTRACT FROM AUTHOR]

Invagination of epithelial sheets to form furrows is a fundamental morphogenetic movement and is found in a variety of developmental events including gastrulation and vertebrate neural tube formation. The cephalic furrow is a deep epithelial invagination that forms during Drosophila gastrulation. In the first phase of cephalic furrow formation, the initiator cells that will lead invagination undergo apicobasal shortening and apical constriction in the absence of epithelial invagination. In the second phase of cephalic furrow formation, the epithelium starts to invaginate, accompanied by both basal expansion and continued apicobasal shortening of the initiator cells. The cells adjacent to the initiator cells also adopt wedge shapes, but only after invagination is well underway. Myosin II does not appear to drive apical constriction in cephalic furrow formation. However, cortical F-actin is increased in the apices of the initiator cells and in invaginating cells during both phases of cephalic furrow formation. These findings suggest that a novel mechanism for epithelial invagination is involved in cephalic furrow formation. [ABSTRACT FROM AUTHOR]

Cell surface expansion is a necessary part of cell shape change. One long-standing hypothesis proposes that membrane for this expansion comes from the flattening out of cell surface projections such as microvilli and membrane folds. Correlative eM data of cells undergoing phagocytosis, cytokinesis, and morphogenesis has hinted at the existence of such an unfolding mechanism for decades; but unfolding has only recently been confirmed using live-cell imaging and biophysical approaches. Considering the wide range of cells in which plasma membrane unfolding has now been reported, it likely represents a fundamental mechanism of cell shape change. [ABSTRACT FROM AUTHOR]

Septate junctions (SJs) serve as occluding barriers in invertebrate epithelia. In Drosophila , at least 30 genes are required for the formation or maintenance of SJs. Interestingly, loss-of-function mutations in core SJ components are embryonic lethal, with defects in developmental events such as head involution and dorsal closure (DC) that occur prior to the formation of a mature SJ, indicating a role for these proteins in mid-embryogenesis independent of their occluding function. To understand this novel function in development, we examined loss-of-function mutations in three core SJ proteins during the process of DC. DC occurs during mid-embryogenesis to seal a dorsal gap in the epidermis following germ band retraction. Closure is driven by contraction of the extraembryonic amnioserosa cells that temporarily cover the dorsal surface and by cell shape changes (elongation) of lateral epidermal cells that bring the contralateral sheets together at the dorsal midline. Using live imaging and examination of fixed tissues, we show that early events in DC occur normally in SJ mutant embryos, but during later closure, coracle , Macroglobulin complement-related and Neurexin-IV mutant embryos exhibit slower rates of closure and display aberrant cells shapes in the dorsolateral epidermis, including dorsoventral length and apical surface area. SJ mutant embryos also show mild defects in actomyosin structures along the leading edge, but laser cutting experiments suggest similar tension and viscoelastic properties in SJ mutant versus wild type epidermis. In a high percentage of SJ mutant embryos, the epidermis tears free from the amnioserosa near the end of DC and live imaging and immunostaining reveal reduced levels of E-cadherin, suggesting that defective adhesion may be responsible for these tears. Supporting this notion, reducing E-cadherin by half significantly enhances the penetrance of DC defects in coracle mutant embryos., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 De, Rice, Zulueta-Coarasa, Fernandez-Gonzalez and Ward.)

Sheets of embryonic epithelial cells coordinate their efforts to create diverse tissue structures such as pits, grooves, tubes, and capsules that lead to organ formation. Such cells can use a number of cell behaviors including contractility, proliferation, and directed movement to create these structures. By contrast, tissue engineers and researchers in regenerative medicine seeking to produce organs for repair or replacement therapy can combine cells with synthetic polymeric scaffolds. Tissue engineers try to achieve these goals by shaping scaffold geometry in such a way that cells embedded within these scaffold self-assemble to form a tissue, for instance aligning to synthetic fibers, and assembling native extracellular matrix to form the desired tissue-like structure. Although self-assembly is a dominant process that guides tissue assembly both within the embryo and within artificial tissue constructs, we know little about these critical processes. Here, we compare and contrast strategies of tissue assembly used by embryos to those used by engineers during epithelial morphogenesis and highlight opportunities for future applications of developmental biology in the field of tissue engineering. [ABSTRACT FROM AUTHOR]

The PDZ-GEF protein Dizzy (Dzy) and its downstream GTPase Rap1 have pleiotropic roles during development of the Drosophila embryo. Here, we show that maternally provided Dzy and Rap1 first function during ventral furrow formation (VFF) where they are critical to guarantee rapid apical cell constrictions. Contraction of the apical actomyosin filament system occurs independently of Dzy and Rap1, but loss of Dzy results in a delayed establishment of the apical adherens junction (AJ) belt, whereas in the absence of Rap1 only a fragmentary apical AJ belt is formed in the epithelium. The timely establishment of apical AJs appears to be essential for coupling actomyosin contractions to cell shape change and to assure completion of the ventral furrow. Immediately after VFF, the downregulation of Dzy and Rap1 is necessary to allow normal mesodermal development to continue after the epithelial-to-mesenchymal transition, as overexpression of Dzy or of constitutively active Rap1 compromises mesodermal migration and monolayer formation. We propose that Dzy and Rap1 are crucial factors regulating the dynamics of AJs during gastrulation. [ABSTRACT FROM AUTHOR]

Abstract: Embryonic development involves global changes in tissue shape and architecture that are driven by cell shape changes and rearrangements within cohesive cell sheets. Morphogenetic changes at the cell and tissue level require that cells generate forces and that these forces are transmitted between the cells of a coherent tissue. Contractile forces generated by the actin–myosin cytoskeleton are critical for morphogenesis, but the cellular and molecular mechanisms of contraction have been elusive for many cell shape changes and movements. Recent studies that have combined live imaging with computational and biophysical approaches have provided new insights into how contractile forces are generated and coordinated between cells and tissues. In this review, we discuss our current understanding of the mechanical forces that shape cells, tissues, and embryos, emphasizing the different modes of actomyosin contraction that generate various temporal and spatial patterns of force generation. [Copyright &y& Elsevier]

Abstract: Inhibition of monocyte and macrophage function by targeting chemokine receptors represents an attractive strategy for therapeutic intervention in inflammatory diseases. We describe an assay to assess chemokine receptor function on whole blood monocytes by measuring chemokine stimulated change in cell shape as measured by flow cytometry. The relative potential of the chemokine receptors CCR1, CCR2, CCR5, CX3CR1, and CXCR4 to activate monocytes in whole blood was evaluated and compared. Analysis of MCP-1 response for monocytes in blood from numerous donors revealed that the assay method had excellent intra-donor reproducibility and sensitivity. Further, the utility of this assay to determine target engagement by chemokine receptor antagonists was demonstrated using a CCR2 antagonist in rhesus monkeys. Blockade of CCR2 on whole blood monocytes was demonstrated ex vivo on blood samples collected from rhesus monkeys administered a small molecule CCR2 antagonist (MK-0812). Using a delayed-type hypersensitivity reaction to elicit monocyte recruitment to the skin of rhesus monkeys, we also evaluated the ability of MK-0812 to block monocyte migration in vivo. Blockade of CCR2 stimulation of whole blood monocytes was correlated with the inhibition of monocyte recruitment to the skin, validating the potential to use this approach in the evaluation of dose selection for chemokine receptor antagonists clinically. [Copyright &y& Elsevier]

Embryonic and early larval surface ciliation patterns are described stage by stage, using scanning electron microscopy and live specimen observations, in 20 species of anuran amphibians from six families including the first detailed description of surface ciliation in a direct-developing eleutherodactylid: four species are from temperate regions and 16 are tropical. The study asks whether differences in pattern relate to ciliation functions, or show any phylogenetic features, or demonstrate heterochrony. It also asks whether the timing of ciliated cell regression is fixed or can vary with the environment. Respiration appears to be the main function of surface ciliation, both pre- and post-hatching, regressing when internal gills become functional. Substratum gliding after hatching may also be a valuable role. Late stage persistence of ciliation around the external nares suggests a sensory function. Localized early regression of ciliated cells is linked to lateral line development. Dramatic changes in ciliated cell shape are described, though functions are unclear. Ciliation patterns, density and duration vary considerably between species, with no obvious phylogenetic or environmental correlates, nor is there a clear relationship with egg size or hatching stage. Ciliation patterns also vary with body region, with density and duration consistently highest round the nostrils and adhesive glands (when present) compared to other body regions. [ABSTRACT FROM AUTHOR]

1: During mast cell degranulation, histamine is released in large quantities. Human eosinophils were found to express histamine H4 but not H3 receptors. The possible effects of histamine on eosinophils and the receptor mediating these effects were investigated in our studies. 2: Histamine (0.01-30?µM) induced a rapid and transient cell shape change in human eosinophils, but had no effects on neutrophils. The maximal shape change was at 0.3?µM histamine with EC50 at 19?nM. After 60?min incubation with 1?µM histamine, eosinophils were desensitized and were refractory to shape change response upon histamine restimulation. Histamine (0.01-1?µM) also enhanced the eosinophil shape change induced by other chemokines. 3: Histamine-induced eosinophil shape change was mediated by the H4 receptor. This effect was completely inhibited by H4 receptor-specific antagonist JNJ 7777120 (IC50 0.3?µM) and H3/H4 receptor antagonist thioperamide (IC50 1.4?µM), but not by selective H1, H2 or H3 receptor antagonists. H4 receptor agonists imetit (EC50 25?nM) and clobenpropit (EC50 72?nM) could mimic histamine effect in inducing eosinophil shape change. 4: Histamine (0.01-100?µM) induced upregulation of adhesion molecules CD11b/CD18 (Mac-1) and CD54 (ICAM-1) on eosinophils. This effect was mediated by the H4 receptor and could be blocked by H4 receptor antagonists JNJ 7777120 and thioperamide. 5: Histamine (0.01-10?µM) induced eosinophil chemotaxis with an EC50 of 83?nM. This effect was mediated by the H4 receptor and could be blocked by H4 receptor antagonists JNJ 7777120 (IC50 86?nM) and thioperamide (IC50 519?nM). Histamine (0.5?µM) also enhanced the eosinophil shape change induced by other chemokines. 6: In conclusion, we have demonstrated a new mechanism of eosinophil recruitment driven by mast cells via the release of histamine. Using specific histamine receptor ligands, we have provided a definitive proof that the H4 receptor mediates eosinophil chemotaxis, cell shape change and upregulation of adhesion molecules. The effect of H4 receptor antagonists in blocking eosinophil infiltration could be valuable for the treatment of allergic diseases. The histamine-induced shape change and upregulation of adhesion molecules on eosinophils can serve as biomarkers for clinical studies of H4 receptor antagonists.British Journal of Pharmacology (2004) 142, 161-171. doi:10.1038/sj.bjp.0705729 [ABSTRACT FROM AUTHOR]

Snake venom metalloproteinases (SVMPs) are structurally and functionally similar to matrix metalloproteinases (MMPs). We have previously demonstrated that a SVMP, named gaminelysin, can induce endothelial cell apoptosis [Biochem J. 357 (2001) 719]. In this study, the action mechanism of graminelysin in causing endothelial cell apoptosis was further investigated. We showed that the apoptosis was initiated with cell shape change and extracellular matrix degradation and occurred before cell detachment. Cleaved forms of MMP-2 might act in concert with graminelysin to cause apoptosis. During apoptosis, adherens junctions, including VE-cadherin and β- and γ-catenin were cleaved and α-catenin was decreased. VE-cadherin and β-catenin at cell periphery were decreased and the discontinuity in alignment was found as observed with immunofluorescence microscopy. This was accompanied with a diffuse β-catenin staining in the cytoplasm and a decreased F-actin stress fibers in some rounded cells. The decrease of VE-cadherin and β-catenin in Triton-insoluble fractions confirmed that the association of adherens junctions with actin cytoskeleton was altered during apoptosis. Graminelysin-induced cleavage in adherens junctions was paralleled with the changes in paracellular permeability. We also detected the activation of caspase-3 and the decrease of Bcl-2/Bax ratio during apoptosis. However, caspase inhibitors showed differential effects in blocking the cleavage of PARP, adherens junctions, and DNA fragmentation. Taken together, the data presented suggest that metalloproteinase can control cell fates via the degradation of matrix proteins, the change of cell shape, and the cleavage of adherens junctions. [Copyright &y& Elsevier]

Dorsal closure is a prominent morphogenetic process during Drosophila embryogenesis, which involves two epithelial tissues, that is, the squamous amnioserosa and the columnar lateral epidermis. Non-muscle myosin II-driven constriction in the amnioserosa leads to a decrease in the apical surface area and pulls on the adjacent lateral epidermis, which subsequently moves dorsally. The pull by the amnioserosa becomes obvious in an elongation of the epidermal cells, especially of those in the first row. The contribution of the epidermal cell elongation has remained unclear to dorsal closure. Cell elongation may be a mere passive consequence or an active response to the pulling by the amnioserosa. Here, we found that the lateral epidermis actively responds. We analyzed tensions within tissues and cell junctions by laser ablation before and during dorsal closure, the elliptical and dorsal closure stages, respectively. Furthermore, we genetically and optochemically induced chronic and acute cell contraction, respectively. In this way, we found that tension in the epidermis increased during dorsal closure. A correspondingly increased tension was not observed at individual junctions, however. Junctional tension even decreased during dorsal closure in the epidermis. We strikingly observed a strong increase of the microtubule amount in the epidermis, while non-muscle myosin II increased in both tissues. Our data suggest that the epidermis actively antagonizes the pull from the amnioserosa during dorsal closure and the increased microtubules might help the epidermis bear part of the mechanical force., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 Lv, Zhang, Zhang, Großhans and Kong.)

A timed series of light micrographs illustrates the process of lorica formation in Dinobryon divergens. Analysis of this series reveals that the Dinobryon cell forms the lorica in two distinct phases: First, the stalk region, without rotation of the cell, and second, the vaseshaped upper part of the lorica, with five slow rotations of the cell yielding the helicoidal band structure of the lorica. Complex changes of shape by the cell body provide the model for lorica diameter. [ABSTRACT FROM AUTHOR]

Summary Contractile forces eliminate cell contacts in many morphogenetic processes. However, mechanisms that balance contractile forces to promote subtler remodeling remain unknown. To address this gap, we investigated remodeling of Drosophila eye lattice cells (LCs), which preserve cell contacts as they narrow to form the edges of a multicellular hexagonal lattice. We found that during narrowing, LC-LC contacts dynamically constrict and expand. Similar to other systems, actomyosin-based contractile forces promote pulses of constriction. Conversely, we found that WAVE-dependent branched F-actin accumulates at LC-LC contacts during expansion and functions to expand the cell apical area, promote shape changes, and prevent elimination of LC-LC contacts. Finally, we found that small Rho GTPases regulate the balance of contractile and protrusive dynamics. These data suggest a mechanism by which WAVE regulatory complex-based F-actin dynamics antagonize contractile forces to regulate cell shape and tissue topology during remodeling and thus contribute to the robustness and precision of the process. [ABSTRACT FROM AUTHOR]

The described protocol is a simple and easily implemented method for making dynamic micropatterns for cell culture. It is based on the use of a surface coating material (azido-PLL-g-PEG (APP)) that initially repels cells, but which can be made strongly adherent by addition of a small functional peptide (BCN-RGD) to the cell culture medium. The method can be applied to trigger the adhesion, migration, or shape change of single cells or of populations of cells, and it can be used to create patterned cocultures. The entire process can be subdivided into three main parts. The first part describes the creation of patterned APP substrates. The second part describes cell seeding and "click" triggering of cell adhesion; the final part describes variations that allow the overlay of multiple patterns or the creation of patterned cocultures. The APP coating of substrates and the triggering of adhesion only involves treating the surface with aqueous stock solutions, allowing any biology lab to adopt this technique., (Copyright © 2014 Elsevier Inc. All rights reserved.)