Convergent extension requires adhesion-dependent biomechanical integration of cell crawling and junction contraction

Convergent extension is an evolutionarily conserved collective cell movement that elongates the body axis of all animals and is required for the morphogenesis of several organ systems. Decades of study have revealed two distinct mechanisms of cell movement during CE, one based on cell crawling and the other on junction contraction. How these two behaviors collaborate during CE is unknown. Here, using quantitative live cell imaging we show that these two modes act both independently and in concert during CE, but that cell movement is more effective when the two modes are simultaneously integrated. Based on these findings, we developed a novel computational model that for the first time treats crawling and contraction independently. This model not only confirmed the biomechanical efficacy of integrating the two modes but also revealed for the first time how the two modes are affected by cell adhesion. Prompted by our modeling, we show that disruption of cell adhesion by knockdown of the Arvcf catenin results in specific failure of integration of crawling with contraction. These data are significant for providing new biomechanical and cell biological insights into a fundamental morphogenetic process implicated in human neural tube defects and skeletal dysplasias.

Self polarization and traveling wave in a model for cell crawling migration

<p style='text-indent:20px;'>In this paper, we prove the existence of traveling wave solutions for an incompressible Darcy's free boundary problem recently introduced in [<xref ref-type="bibr" rid="b6">6</xref>] to describe cell motility. This free boundary problem involves a nonlinear destabilizing term in the boundary condition which describes the active character of the cell cytoskeleton. By using two different methods, a constructive method via a graph analysis and a local bifurcation method, we prove that traveling wave solutions exist when the destabilizing term is strong enough.</p>

Conserved actin machinery drives microtubule-independent motility and phagocytosis in Naegleria

Much of our understanding of actin-driven phenotypes in eukaryotes has come from the “yeast-to-human” opisthokont lineage and the related amoebozoa. Outside of these groups lies the genus Naegleria, which shared a common ancestor with humans &gt;1 billion years ago and includes the “brain-eating amoeba.” Unlike nearly all other known eukaryotic cells, Naegleria amoebae lack interphase microtubules; this suggests that actin alone drives phenotypes like cell crawling and phagocytosis. Naegleria therefore represents a powerful system to probe actin-driven functions in the absence of microtubules, yet surprisingly little is known about its actin cytoskeleton. Using genomic analysis, microscopy, and molecular perturbations, we show that Naegleria encodes conserved actin nucleators and builds Arp2/3–dependent lamellar protrusions. These protrusions correlate with the capacity to migrate and eat bacteria. Because human cells also use Arp2/3–dependent lamellar protrusions for motility and phagocytosis, this work supports an evolutionarily ancient origin for these processes and establishes Naegleria as a natural model system for studying microtubule-independent cytoskeletal phenotypes.

Hydrodynamic effects on the motility of crawling eukaryotic cells

We study how hydrodynamics can alter cell crawling, extending the simple three-sphere swimmer to include adhesion to a substrate.

Collective dynamics of coherent motile cells on curved surfaces

Collective cell crawling on curved surfaces can exhibit diverse dynamic patterns including global rotation, local swirling, spiral crawling, and serpentine crawling, depending on cell–cell interactions and geometric constraints.

Numerical solutions of a 2D fluid problem coupled to a nonlinear non-local reaction-advection-diffusion problem for cell crawling migration in a discoidal domain

In this work, we present a numerical scheme for the approximate solutions of a 2D crawling cell migration problem. The model, defined on a non-deformable discoidal domain, consists in a Darcy fluid problem coupled with a Poisson problem and a reaction-advection-diffusion problem. Moreover, the advection velocity depends on boundary values, making the problem nonlinear and non local. For a discoidal domain, numerical solutions can be obtained using the finite volume method on the polar formulation of the model. Simulations show that different migration behaviours can be captured.