Biology subjects

David, N. B.

Publications and source records attributed to David, N. B..

6 recordsLinked to original sources

bioRxiv2023

Inactivating Negative Regulators of Cortical Branched Actin Enhances Persistence of Single Cell Migration

The Rac1-WAVE-Arp2/3 pathway pushes the plasma membrane by polymerizing branched actin at the cell cortex and thereby powering membrane protrusions that mediate cell migration. Here, using knock-down (KD) or knock-out (KO), we combine the inactivation of the Arp2/3 inhibitory protein Arpin, the Arp2/3 subunit ARPC1A and the WAVE complex subunit, CYFIP2, that all enhance the polymerization of cortical branched actin (CBA). Inactivation of the 3 CBA negative regulators increases migration persistence of human breast MCF10A cells, and of endodermal cells in the zebrafish embryo, significantly more than any single or double inactivation. In the triple KO, but not triple KD cells, the "super-migrator" phenotype was associated with a heterogenous down-regulation of vimentin expression and a lack of coordination in collective behaviors, such as wound healing and acinus morphogenesis. Re-expression of vimentin in triple KO cells restored the normal persistence of single cell migration to a large extent, suggesting that vimentin down-regulation is one of the adjustments in gene expression through which the super-migrator phenotype is stably maintained in triple KO cells. Constant excessive production of branched actin at the cell cortex thus commits cells into a motile state through changes in gene expression.

cell biology↗

bioRxiv2023

Necrosulfonamide causes ubiquitination of PCM1 and impairs Ciliogenesis and Autophagy

Centriolar satellites are high-order assemblies, scaffolded by the protein PCM1, that gravitate as particles around the centrosome and play pivotal roles in fundamental cellular processes notably ciliogenesis and autophagy. Despite stringent control mechanisms involving phosphorylation and ubiquitination, the landscape of post-translational modifications shaping these structures remains elusive. Here, we report that necrosulfonamide (NSA), a small molecule known for binding and inactivating the pivotal effector of cell death by necroptosis MLKL, intersects with centriolar satellites, ciliogenesis, and autophagy independently of MLKL. NSA functions as a potent redox cycler and triggers the oxidation and aggregation of PCM1 alongside select partners, while minimally impacting the overall distribution of centriolar satellites. Additionally, NSA-mediated ROS production disrupts ciliogenesis and leads to the accumulation of autophagy markers, partially alleviated by PCM1 deletion. Together, these results identify PCM1 as a redox sensor protein and provide new insights into the interplay between centriolar satellites and autophagy.

cell biology↗

bioRxiv2023

Collective cell migration due to guidance-by-followers is robust to multiple stimuli

Collective cell migration is an important process during biological development and tissue repair, but may turn malignant during tumor invasion. Mathematical and computational models are essential to unravel the mechanisms of self-organization that underlie the emergence of collective migration from the interactions among individual cells. Recently, guidance-by-followers was identified as one such underlying mechanism of collective cell migration in the zebrafish embryo. This poses the question how guidance stimuli are integrated when multiple cells interact simultaneously. Here, we extend a recent individual-based model by an integration step of the vectorial guidance stimuli and compare model predictions obtained for various variants of the mechanism (arithmetic mean of stimuli, dominance of stimulus with largest transmission interface, dominance of most head-on stimulus). Simulations are carried out and quantified within the modeling and simulation framework Morpheus. Collective cell migration is sfound to be robust and qualitatively identical for all considered variants of stimulus integration. Moreover, this study highlights the role of individual-based modeling approaches for understanding collective phenomena at the population scale that emerge from cell-cell interactions.

developmental biology↗

bioRxiv2023

Nhsl1b regulates mesodermal cell migration by controlling protrusion dynamics during zebrafish gastrulation.

Cell migrations are crucial for embryonic development, wound healing, the immune response, as well as for cancer progression. During mesenchymal cell migration, the Rac1-WAVE-Arp2/3 signalling pathway induces branched actin polymerisation, which protrudes the membrane and allows migration. Fine-tuning the activity of the Rac1-WAVE-Arp2/3 pathway modulates protrusion lifetime and migration persistence. Recently, NHSL1, a novel interactor of the Scar/WAVE complex has been identified as a negative regulator of cell migration in vitro. We here analysed its function in vivo, during zebrafish gastrulation, when nhsl1b is specifically expressed in migrating mesodermal cells. Loss and gain of function experiments revealed that nhsl1b is required for the proper migration of the mesoderm, controlling cell speed and migration persistence. Nhsl1b localises to the tip of actin-rich protrusions where it controls protrusion dynamics, its loss of function reducing the length and lifetime of protrusions, whereas overexpression has the opposite effect. Within the protrusion, Nhsl1b knockdown increases F-actin assembly rate and retrograde flow. These results identify Nhsl1b as a cell type specific regulator of cell migration and highlight the importance of analysing the function of regulators of actin dynamics in physiological contexts.

cell biology↗

bioRxiv2021

Guidance by followers ensures long-range coordination of cell migration through α-Catenin mechanoperception

Morphogenesis, wound healing and some cancer metastases depend upon migration of cell collectives that need to be guided to their destination as well as coordinated with other cell movements. During zebrafish gastrulation, extension of the embryonic axis is led by the mesendodermal polster that migrates towards the animal pole, followed by axial mesoderm that undergoes convergence and extension. We here investigate how polster cells are guided towards the animal pole. Using a combination of precise laser ablations, advanced transplants and functional as well as in silico approaches, we establish that each polster cell is oriented by its immediate follower cells. Each cell perceives the migration of followers, through E-Cadherin/-Catenin mechanotransduction, and aligns with them. Directional information therefore propagates from cell to cell over the whole tissue. Such guidance of migrating cells by followers ensures long-range coordination of movements and developmental robustness.

developmental biology↗

bioRxiv2020

CYFIP2 containing WAVE complexes inhibit cell migration

Branched actin networks polymerized by the Arp2/3 complex are critical for cell migration. The WAVE complex is the machinery that activates Arp2/3 in a RAC1-dependent manner at the leading edge of migrating cells. Multiple WAVE complexes are assembled in a cell through various combinations of paralogous subunits. Here we report the surprising phenotype associated with loss-of-function of CYFIP2, a subunit of the WAVE complex. In three different human mammary cell lines and in prechordal plate cells of gastrulating zebrafish embryos, CYFIP2 depletion promoted, rather than impaired, membrane protrusions and migration persistence. CYFIP2, however, assembled WAVE complexes that polymerize branched actin at the cell cortex and rescued membrane protrusions of CYFIP1/2 double knock-out cells, although less efficiently than CYFIP1. Point mutations of CYFIP2 associated with intellectual disability in children were gain-of-function, as they made CYFIP2 as active as CYFIP1 in this rescue experiment. Biochemical reconstitutions of CYFIP2-containing WAVE complexes showed that they bound equally well to active RAC1 as CYFIP1-containing WAVE complexes, yet they were poorly activated in response to RAC1 binding. Together these results suggest that CYFIP2-containing WAVE complexes titrate active RAC1 and thereby prevent efficient CYFIP1-containing complexes from being activated. In this context, where cell migration is governed by the balance of CYFIP1/2 expression, releasing the restrained activity of CYFIP2-containing WAVE complexes leads to pathology.

cell biology↗