Biology subjects

Czirok, A.

Publications and source records attributed to Czirok, A..

4 recordsLinked to original sources

bioRxiv2020

Theoretical analysis of neural crest cell migration

The neural crest cells are embryonic stem cells that migrate throughout embryos and, at different target locations, give rise to the formation of a variety of tissues and organs. The directional migration of the neural crest cells is experimentally described using a process referred to as contact inhibition of locomotion (CIL), by which cells redirect their movement upon the cell-cell contacts. However, it is unclear how the migration alignment is affected by the motility properties of the cells. Here, we computationally model the migration alignment and the average time to reach a target location as functions of the motility dynamics and interaction of the cells in an open domain with a channel geometry. The results indicate that by varying the properties of the CIL interaction a transition takes place from random movement of the cells to an organized collective migration, where the migration alignment is maximised and the migration time is minimised. This phase transition is accelerated and strengthened with the influx rate of the cells into the domain through increasing the density of the migrating cells. The model further suggests that the migration is more coordinated when the cells with a large CIL radius move fast in a narrow domain.

biophysics↗

bioRxiv2020

Multiscale modelling of motility wave propagation in cell migration

The collective motion of cell monolayers within a tissue is a fundamental biological process that occurs during tissue formation, wound healing, cancerous invasion, and viral infection. Experiments have shown that at the onset of migration, the motility is self-generated as a polarization wave starting from the leading edge of the monolayer and progressively propagates into the bulk. However, it is unclear how the propagation of this motility wave is influenced by cellular properties. Here, we investigate this using a computational model based on the Potts model coupled to the dynamics of intracellular polarization. The model captures the propagation of the polarization wave initiated at the leading edge and suggests that the cells cortex can regulate the migration modes: strongly contractile cells may depolarize the monolayer, whereas less contractile cells can form swirling movement. Cortical contractility is further found to limit the cells motility, which (i) decelerates the wave speed and the leading edge progression, and (ii) destabilises the leading edge into migration fingers. Together, our model describes how different cellular properties can contribute to the regulation of collective cell migration.

biophysics↗

bioRxiv2019

SPECC1L-deficient palate mesenchyme cells show speed and directionality defect

Clefts of the lip and/or palate (CL/P) are common anomalies that occur in 1/800 live births. Pathogenic SPECC1L variants identified in patients with rare atypical clefts and syndromic CL/P suggest the gene plays a primary role in face and palate development. We have generated Specc1l gene-trap (Specc1lcGT) and truncation (Specc1l{Delta}C510) alleles that cause embryonic or perinatal lethality, respectively. Specc1lcGT/{Delta}C510 compound mutants show delayed and abnormal palatal shelf elevation at E14.5. By E15.5, the mutant shelves do elevate and fuse, however, the palatal rugae form abnormally. Palatogenesis requires extensive mesenchymal remodeling, especially during palatal shelf elevation. We posit that this remodeling involves collective movement of neural crest-derived palatal mesenchyme cells. Live time-lapse microscopy was performed to visualize in vitro wound-repair assays with wildtype and SPECC1L-deficient primary mouse embryonic palatal mesenchyme (MEPM) cells. SPECC1L-deficient MEPM cells consistently showed delayed closure in wound-repair assays. To evaluate which features of cellular movement were responsible, we performed automated particle image velocimetry (PIV) and manual cell tracking. The analyses revealed that both cell speed and directionality are disrupted in SPECC1L-deficient cells compared to controls. To determine if primary MEPM cells can move collectively, we assayed stream formation, which is a hallmark of collective movement. Indeed, MEPM cultures displayed correlated movement of neighboring cells. Importantly, correlation length was reduced in SPECC1L-deficient cultures, consistent with a role for SPECC1L in collective migration. Furthermore, we demonstrated that activation of the PI3K-AKT pathway with the 740Y-P small molecule can rescue the wound-closure delay in SPECC1L-deficient MEPM cells. Cell tracking analyses showed that this rescue was due to both increased speed and improved directionality. Altogether, our data showed a novel role for SPECC1L in guided movement through modulation of PI3K-AKT signaling.

cell biology↗

bioRxiv2019

Viscoelastic properties of ECM-rich embryonic microenvironments

The material properties of tissues and their mechanical state is an important factor during development, disease, regenerative medicine and tissue engineering. Here we describe a microrheological measurement technique utilizing aggregates of microinjected ferromagnetic nickel particles to probe the viscoelastic properties of embryonic tissues. Quail embryos were cultured in a plastic incubator chamber located at the center of two pairs of crossed electromagnets. We estimate the Youngs modulus of the ECM-rich region separating the mesoderm and endoderm in Hamburger Hamilton stage 6-10 quail embryos as 300{+/-}100 Pa. We found a pronounced viscoelastic behavior consistent with a Zener (standard generalized solid) model. The viscoelastic response is about 45% of the total response, with a characteristic relaxation time of 1.3 sec.

developmental biology↗