Cell Blebbing in Confined Microfluidic Environments

Ibo, Markela; Srivastava, Vasudha; Robinson, Douglas N.; Gagnon, Zachary

doi:10.1371/journal.pone.0163866

Cited by 29 publications

(35 citation statements)

References 53 publications

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“…The interplay between adhesion, confinement, and cortical contractility has been explored systematically by Liu and colleagues 47 , who suggest that these three parameters integrate to determine the mechanism of migration. Similarly, in Dictyostelium, confinement itself is sufficient to induce rapid changes between blebbing and pseudopod-mediated migration 48 . In this context, reducing confinement by increasing the height of a microfluidic channel through which the cells are migrating is associated with a rapid loss of blebs and an increase in pseudopod formation.…”

Section: Discussionmentioning

confidence: 99%

A sheath of motile cells supports collective migration in of the Zebrafish posterior lateral line primordium under the skin

Nogare

Natesh

Chitnis

2019

Preprint

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During embryonic development, cells must navigate through diverse three-dimensional environments robustly and reproducibly. The zebrafish posterior lateral line primordium (PLLp), a group of approximately 120 cells which migrates from the otic vesicle to the tip of the tail, spearheading the development of the lateral line sensory system, is an excellent model to study such collective migration in an in vivo context. This system migrates in a channel formed by the underlying horizontal myoseptum and somites, and the overlying skin. While cells in the leading part of the PLLp are flat and have a more mesenchymal morphology, cells in the trailing part progressively reorganize to form epithelial rosettes, called protoneuromasts. These epithelial cells extend basal cryptic lamellipodia in the direction of migration in response to both chemokine and FGF signals. In this study, we show that, in addition to these cryptic lamellipodia, the core epithelial cells are in fact surrounded by a population of motile cells which extend actin-rich migratory processes apposed to the overlying skin. These thin cells wrap around the protoneuromasts, forming a continuous sheath of cells around the apical and lateral surface of the PLLp. The processes extended by these cells are highly polarized in the direction of migration and this directionality, like that of the basal lamellipodia, is dependent on FGF signaling. Consistent with interactions of sheath cells with the overlying skin contributing to migration, removal of the skin stalls migration. However, this is accompanied by some surprising changes. There is a profound change in the morphology of the sheath cells, with directional superficial lamellipodia being replaced with the appearance of undirected blebs or ruffles. Furthermore, removal of the skin not only affects underlying lamellipodia, it simultaneously alters the morphology and behavior of the deeper basal cryptic lamellipodia, even though these cells do not directly contact the skin. Directional actin-rich protrusions on both the apical and basal surface and migration are completely and simultaneously restored upon regrowth of the skin over the PLLp. We suggest that this system utilizes a circumferential sheath of motile cells to allow the internal epithelial cells to migrate collectively in the confined space of the horizontal myopseptum and that elastic confinement provided by the overlying skin is essential for effective collective migratory behavior of primordium cells.

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Section: Discussionmentioning

confidence: 99%

A sheath of motile cells supports collective migration in of the Zebrafish posterior lateral line primordium under the skin

Nogare

Natesh

Chitnis

2019

Preprint

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“…An ideal site for studying the generation of outward forces is the leading edge of a migrating cell. At this edge, the forward-driving force is driven either by the well-defined Arp2/3 Brownian ratchet (26)(27)(28) or by pressure-induced bleb formation due to myosin activity in highly confined, compressed environments (29,30). The Arp2/3 Brownian ratchet moves the plasma membrane forward by stimulating the creation of many new actin filament branches at the leading edge.…”

Section: Forces Acting On the Cell Cortexmentioning

confidence: 99%

“…In another type of motility, termed lobopodial migration, cells in confined environments pull their nuclei forward by myosin II contraction, using the nucleus as a piston to create enough pressure to drive bleb formation at the cell front (31). These blebs then rapidly fill with actin-cytoskeletal components, creating a new cortex (29,30). In both cases, the process that allows faster membrane protrusion should determine the dominant behavior.…”

Section: Forces Acting On the Cell Cortexmentioning

confidence: 99%

Mechanochemical Signaling Directs Cell-Shape Change

Schiffhauer

Robinson

2017

Biophysical Journal

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For specialized cell function, as well as active cell behaviors such as division, migration, and tissue development, cells must undergo dynamic changes in shape. To complete these processes, cells integrate chemical and mechanical signals to direct force production. This mechanochemical integration allows for the rapid production and adaptation of leading-edge machinery in migrating cells, the invasion of one cell into another during cell-cell fusion, and the force-feedback loops that ensure robust cytokinesis. A quantitative understanding of cell mechanics coupled with protein dynamics has allowed us to account for furrow ingression during cytokinesis, a model cell-shape-change process. At the core of cell-shape changes is the ability of the cell's machinery to sense mechanical forces and tune the force-generating machinery as needed. Force-sensitive cytoskeletal proteins, including myosin II motors and actin cross-linkers such as a-actinin and filamin, accumulate in response to internally generated and externally imposed mechanical stresses, endowing the cell with the ability to discern and respond to mechanical cues. The physical theory behind how these proteins display mechanosensitive accumulation has allowed us to predict paralogspecific behaviors of different cross-linking proteins and identify a zone of optimal actin-binding affinity that allows for mechanical stress-induced protein accumulation. These molecular mechanisms coupled with the mechanical feedback systems ensure robust shape changes, but if they go awry, they are poised to promote disease states such as cancer cell metastasis and loss of tissue integrity.The concept ''form begets function begets form'' provides an excellent foundation for understanding the behavior of biological systems. Even specialized cells, the smallest unit of complex living systems, perform all of the necessary functions of an organism by assuming distinct shapes, mechanical properties, and physical behaviors. Different cell types use a common set of cytoskeletal elements to provide precise physical support for their distinct functions. For example, red blood cells and neurons have very different shapes that allow them to perform their specific roles. However, they both utilize alternating patterns of actin and spectrin to form cortices with appropriate viscous and elastic properties, albeit in different structural arrangements. Perturbations to this structural network cause a breakdown in the mechanical properties, or the form, of these cells, which inhibits cell function (1,2).Fascinatingly, the physical properties of cells are both determined and acted upon by the cytoskeletal apparatus. Cells are capable of modifying their own physical properties and driving changes in cell shape in response to internal and external chemical and mechanical stimuli. These modifications occur through the remodeling of the cell cortex, the network of cytoskeletal proteins directly under the plasma membrane. Much progress has been made recently in deciphering how chemical signa...

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“…Blebs have been studied from several viewpoints. They may be described as 17 geometric objects (Euclidean) [11], the result of forces on a smooth manifold 18 (differential geometry) [12][13][14][15], the result of physical force (pressure) [16][17][18][19], the result 19 of cortical tension (related to pressure) [6] and the result of fluid dynamics [20,21]. In 20 spite of the substantial progress made in the study of bleb-based motility, the precise 21 mechanism by which cytoskeletal proteins interact with biophysical and geometric forces 22 to generate blebs and coordinate cell movement using these protrusions is still unclear.…”

mentioning

confidence: 99%

“…The value of our pressure term reflects the local activity of myosin II in the cell 277 cortex. Local pressure increases as a result of cortex contraction by myosin II [2,34,35]. 278 In constrast to [15], we take the point of view that equilibration of this pressure is not 279 perfectly efficient, resulting in short lived spatial variations on a time scale consistent 280 with bleb nucleation.…”

mentioning

confidence: 99%

A bleb initiation model for chemotaxis suggests a role for myosin II clusters and cortex rupture

Asante-Asamani

Grange

Rawal

et al. 2020

Preprint

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Blebs, pressure driven protrusions of the plasma membrane, facilitate the movement of cells such as the soil amoeba Dictyostelium discoideum and other eukaryotes such as white blood cells and cancer cells. Blebs initiate or nucleate when proteins connecting the membrane to the cortex detach, either as a result of a rupture of the cortex or as a direct consequence of a build up in hydrostatic pressure. While linker detachment resulting from excess hydrostatic pressure is well understood, the mechanism by which cells rupture their cortex in locations of bleb formation is not so clear. Consequently, existing predictive models of bleb site selection do not account for it. To resolve this, we propose a model for bleb initiation which combines the geometric forces on the cell cortex/membrane complex with the underlying activity of actin binding proteins. In our model gaps, resulting from a rupture of the cortex, form at locations of high membrane energy where an accumulation of myosin II helps to weaken the cortex. We validate this model in part through a membrane energy functional which combines stresses on the cell boundary from membrane tension, curvature, membrane-cortex linker tension with hydrostatic pressure. Application of this functional to microscopy images of chemotaxing Dictyostelium discoideum cells identifies bleb nucleation sites at the highest energy locations 96.7% of the time. Sensitivity analysis of the model components points to membrane tension and hydrostatic pressure, all of which are regulated by myosin II, as critical to model predictability. Furthermore, microscopy reveals discrete clusters of myosin II along the leading edge of the cell, with blebs emerging from 80% of these sites. Together, our findings suggest a critical role for myosin II in bleb initiation through the formation of gaps and provides a predictive mathematical model for quantitative studies of blebbing. Author summaryEukaryotic cells such as white blood cells and cancer cells have been observed to move by making spherical herniation of their plasma membrane, referred to as blebs. The precise mechanism by which cells select locations around their boundary to initiate blebs is unclear. We hypothesize that blebs initiate at locations of high membrane energy where an accumulation of myosin II helps to rupture the cortex and/or detach linker proteins. We test this hypothesis by formulating a free energy functional representation of membrane energy to predict where blebs will initiate. The functional March 16, 2020 1/19 accounts for geometric forces due to membrane tension, curvature and membrane-cortex linker tension as well as hydrostatic pressure. Application of the functional to data from the soil amoeba, Dictyostelium disodium, identifies blebs at the highest energy locations over 90% of the time. Sensitivity analysis of model components points to membrane tension and hydrostatic pressure, all influenced by myosin II, as major forces driving bleb initiation. Additionally, we observe clusters of myosin II at locations of bleb ...

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Cell Blebbing in Confined Microfluidic Environments

Cited by 29 publications

References 53 publications

A sheath of motile cells supports collective migration in of the Zebrafish posterior lateral line primordium under the skin

A sheath of motile cells supports collective migration in of the Zebrafish posterior lateral line primordium under the skin

Mechanochemical Signaling Directs Cell-Shape Change

A bleb initiation model for chemotaxis suggests a role for myosin II clusters and cortex rupture

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