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Scientists have discovered an unexpected link between the shape of a cell and its migration efficiency, and they’ve explained its physics using a model of a liquid droplet.
Cell migration is achieved through the movement of the cell’s membrane, which is powered by the action of a protein network inside the cell.
This interaction is affected by the cell’s overall shape, but exactly how this takes place has been unclear.
Research published in Current Biology provides some insight.
The first step in cell migration occurs when the cell extends its front edge—a process called protrusion. This is driven by the growth of actin filaments, which push the cell membrane from inside. At the same time, membrane tension controls protrusion by providing resistance and protecting the cell from over-extending.
But physical laws dictate that the shape of the cell membrane must play a role in the balance between force exerted by actin and the resisting membrane tension. This was not taken into account in previous studies, which used 2D models of migrating cells.
Now, Chiara Gabella, PhD, of Ecole Polytechnique Fédérale de Lausanne in Switzerland, and her colleagues have used a 3D model to better describe the relationship between cell protrusion, shape, and membrane tension.
The scientists developed a way to evaluate the 3D shape of migrating fish epidermal keratocytes by observing the cells in a chamber filled with a fluorescent solution.
The team applied various treatments to swell, shrink, or stretch the cells. And they were able to observe the treatment’s impact on membrane tension, shape, and protrusion velocity.
The treatments only affected the cells’ shape and migration speed, not membrane tension. The results also showed that the more spherical a cell is, the faster it moves.
To interpret these unexpected findings, the scientists modeled a migrating cell as a liquid droplet spreading on a surface.
“It is well known that a droplet’s shape and, in particular, the contact angle that it makes with the surface are determined by the tension forces between the droplet, its environmental medium (eg, air or a different liquid), and the surface on which it moves,” Dr Gabella said.
Results of the modeling experiment suggested that the leading edge could be considered a triple interface between the substrate, membrane, and extracellular medium. And the contact angle between the membrane and the substrate determines the load on actin polymerization and, therefore, the protrusion rate.
“From this point of view, a more spherical cell means less load for actin filaments to overcome and, therefore, faster actin growth and migration,” said Alexander Verkhovsky, PhD, also of Ecole Polytechnique Fédérale de Lausanne.
In support of this idea, the scientists found the cells were sensitive to the surface characteristics, just as droplets would be, by slowing down or being pinned at ridges.
“The emphasis of many studies has been on discovering and characterizing individual cellular components,” Dr Verkhovsky said. “This is rooted in the common belief that a cell’s behavior is determined by intricate networks of genes and proteins.”
In contrast, this work shows that, despite their molecular complexity, cells can be described as physical objects. The findings point to a new relationship between a cell’s shape and its dynamics and may help us to understand how cell migration is guided by the cell’s 3D environment. 
Scientists have discovered an unexpected link between the shape of a cell and its migration efficiency, and they’ve explained its physics using a model of a liquid droplet.
Cell migration is achieved through the movement of the cell’s membrane, which is powered by the action of a protein network inside the cell.
This interaction is affected by the cell’s overall shape, but exactly how this takes place has been unclear.
Research published in Current Biology provides some insight.
The first step in cell migration occurs when the cell extends its front edge—a process called protrusion. This is driven by the growth of actin filaments, which push the cell membrane from inside. At the same time, membrane tension controls protrusion by providing resistance and protecting the cell from over-extending.
But physical laws dictate that the shape of the cell membrane must play a role in the balance between force exerted by actin and the resisting membrane tension. This was not taken into account in previous studies, which used 2D models of migrating cells.
Now, Chiara Gabella, PhD, of Ecole Polytechnique Fédérale de Lausanne in Switzerland, and her colleagues have used a 3D model to better describe the relationship between cell protrusion, shape, and membrane tension.
The scientists developed a way to evaluate the 3D shape of migrating fish epidermal keratocytes by observing the cells in a chamber filled with a fluorescent solution.
The team applied various treatments to swell, shrink, or stretch the cells. And they were able to observe the treatment’s impact on membrane tension, shape, and protrusion velocity.
The treatments only affected the cells’ shape and migration speed, not membrane tension. The results also showed that the more spherical a cell is, the faster it moves.
To interpret these unexpected findings, the scientists modeled a migrating cell as a liquid droplet spreading on a surface.
“It is well known that a droplet’s shape and, in particular, the contact angle that it makes with the surface are determined by the tension forces between the droplet, its environmental medium (eg, air or a different liquid), and the surface on which it moves,” Dr Gabella said.
Results of the modeling experiment suggested that the leading edge could be considered a triple interface between the substrate, membrane, and extracellular medium. And the contact angle between the membrane and the substrate determines the load on actin polymerization and, therefore, the protrusion rate.
“From this point of view, a more spherical cell means less load for actin filaments to overcome and, therefore, faster actin growth and migration,” said Alexander Verkhovsky, PhD, also of Ecole Polytechnique Fédérale de Lausanne.
In support of this idea, the scientists found the cells were sensitive to the surface characteristics, just as droplets would be, by slowing down or being pinned at ridges.
“The emphasis of many studies has been on discovering and characterizing individual cellular components,” Dr Verkhovsky said. “This is rooted in the common belief that a cell’s behavior is determined by intricate networks of genes and proteins.”
In contrast, this work shows that, despite their molecular complexity, cells can be described as physical objects. The findings point to a new relationship between a cell’s shape and its dynamics and may help us to understand how cell migration is guided by the cell’s 3D environment.
Scientists have discovered an unexpected link between the shape of a cell and its migration efficiency, and they’ve explained its physics using a model of a liquid droplet.
Cell migration is achieved through the movement of the cell’s membrane, which is powered by the action of a protein network inside the cell.
This interaction is affected by the cell’s overall shape, but exactly how this takes place has been unclear.
Research published in Current Biology provides some insight.
The first step in cell migration occurs when the cell extends its front edge—a process called protrusion. This is driven by the growth of actin filaments, which push the cell membrane from inside. At the same time, membrane tension controls protrusion by providing resistance and protecting the cell from over-extending.
But physical laws dictate that the shape of the cell membrane must play a role in the balance between force exerted by actin and the resisting membrane tension. This was not taken into account in previous studies, which used 2D models of migrating cells.
Now, Chiara Gabella, PhD, of Ecole Polytechnique Fédérale de Lausanne in Switzerland, and her colleagues have used a 3D model to better describe the relationship between cell protrusion, shape, and membrane tension.
The scientists developed a way to evaluate the 3D shape of migrating fish epidermal keratocytes by observing the cells in a chamber filled with a fluorescent solution.
The team applied various treatments to swell, shrink, or stretch the cells. And they were able to observe the treatment’s impact on membrane tension, shape, and protrusion velocity.
The treatments only affected the cells’ shape and migration speed, not membrane tension. The results also showed that the more spherical a cell is, the faster it moves.
To interpret these unexpected findings, the scientists modeled a migrating cell as a liquid droplet spreading on a surface.
“It is well known that a droplet’s shape and, in particular, the contact angle that it makes with the surface are determined by the tension forces between the droplet, its environmental medium (eg, air or a different liquid), and the surface on which it moves,” Dr Gabella said.
Results of the modeling experiment suggested that the leading edge could be considered a triple interface between the substrate, membrane, and extracellular medium. And the contact angle between the membrane and the substrate determines the load on actin polymerization and, therefore, the protrusion rate.
“From this point of view, a more spherical cell means less load for actin filaments to overcome and, therefore, faster actin growth and migration,” said Alexander Verkhovsky, PhD, also of Ecole Polytechnique Fédérale de Lausanne.
In support of this idea, the scientists found the cells were sensitive to the surface characteristics, just as droplets would be, by slowing down or being pinned at ridges.
“The emphasis of many studies has been on discovering and characterizing individual cellular components,” Dr Verkhovsky said. “This is rooted in the common belief that a cell’s behavior is determined by intricate networks of genes and proteins.”
In contrast, this work shows that, despite their molecular complexity, cells can be described as physical objects. The findings point to a new relationship between a cell’s shape and its dynamics and may help us to understand how cell migration is guided by the cell’s 3D environment.