Biology subjects

Lachuer, H.

Publications and source records attributed to Lachuer, H..

9 recordsLinked to original sources

bioRxiv2026

Endosomal membrane state governs trafficking and cell migration under TFEB control

Transcription Factor EB (TFEB) regulates the biogenesis of lysosomes, which are acidic organelles of the endosomal network. While its role in cellular clearance is well established, the pleiotropic functions of TFEB across diverse cellular processes, as well as its activation in several cancer types, remain incompletely understood. Investigating TFEB in a bladder cancer model, we found that its depletion selectively impaired cell migration and adhesion. This phenotype was associated with the retention of the adhesion molecule integrin {beta}5 (ITG{beta}5), in central intracellular compartments identified as multivesicular bodies (MVBs) upon TFEB knockdown (KD). Mechanistically, TFEB regulated cellular lipid composition and membrane fluidity of acidic endosomes that controlled ITG{beta}5 trafficking. Remarkably, exogenous supplementation with a monounsaturated fatty acid (MUFA) that increased MVB membrane fluidity was sufficient to phenocopy the intracellular trapping of ITG{beta}5 in 2D culture and 3D tumoroids. We further showed that TFEB-dependent maintenance of MVB membrane fluidity relies on ESCRT-0 subcomplex, HGS/Hrs, which retains cholesterol at MVBs. Together, these findings reveal how transcriptional programs shape endosomal membrane states to control cargo trafficking and cell behavior.

cell biology↗

bioRxiv2026

Softer when Thicker: a Conserved Scaling Law Governs Actin Cortex Mechanics

Scaling laws are powerful tools in material science to relate geometric and mechanical properties of materials. The actin cortex, a dynamic network beneath the plasma membrane, is essential for cellular morphogenesis, force generation, and tissue organization. Despite its critical role, the mechanical properties of the cortex itself remain poorly understood. Using the magnetic pincher, a new technique we recently developed, we directly measure the thickness (h) and elastic modulus (E) of the actin cortex in live cells, uncovering a universal scaling (E ~ h-2) across multiple cell types. Drawing an analogy to cellular solids, common in nature and material science, we identified an origin for this scaling: the volume fraction of actin filaments varies concomitantly with the cortex thickness, due to a conservation of filamentous actin quantity. Thus thinner cortices exhibit higher actin density and stiffness, while thicker cortices are sparser and softer. The relationship holds under diverse perturbations targeting myosin contractility, actin nucleation, and turnover, but is lost upon actin disassembly, highlighting its dependence on the intact actin network. Our results establish that cells, across cell types, function within a rather limited range of quantity of cortical actin filaments and primarily modulate cortex thickness to tune mechanical properties, with profound implications for cell shape regulation, tissue mechanics, and the interpretation of indentation-based mechanical measurements.

biophysics↗

bioRxiv2026

Epithelial density controls cell migration through an adhesion-nucleus mechanotransduction pathway

Cell density is thought to regulate tissue growth, homeostasis, and regeneration, yet how cells sense and respond to density remains poorly understood. To investigate density-dependent mechanotransduction, we combined genetically encoded biosensors with quantitative fluorescence microscopy in epithelial cells subjected to genetic, pharmacological, and mechanical perturbations. We found that low epithelial density promotes focal adhesion growth, causing mechanical relaxation of vinculin and release of its competitive binding with FAK and ERK. This enables FAK to bind and activate ERK in the cytoplasm. Cytoskeletal tension transmitted through LINC complexes drives their nuclear translocation, where low density induces ERK-dependent chromatin decondensation and increased nuclear envelope tension. This recruits and activates cPLA2, leading to arachidonic acid production and enhanced cell migration. Together, these findings identify a mechanochemical pathway linking cell density to epithelial migration via ERK, cPLA2, and mechanically regulated signaling from adhesions to the nucleus. Significance statementIn multicellular organisms, cells constantly experience crowding, yet how they detect changes in cell density and convert them into biological responses is not well understood. Here, we show how low cell density mechanically triggers signaling inside epithelial cells to promote migration. When cells are sparse, adhesion sites grow and release key signaling proteins that move into the nucleus stretched by the cytoskeleton. These mechanical and biochemical inputs alter nuclear structure, activates lipid signaling, and boosts cell migration. By revealing how mechanical forces, cell adhesions, and nuclear signaling work together, this study provides a clear mechanistic link between cell density and migration, a process central to tissue growth, repair, and disease progression.

cell biology↗

bioRxiv2025

Nuclear pore complex distribution on the nuclear envelope: insights into curvature, chromatin, and actin contributions

The Nuclear Pore Complex (NPC) is an ancestral feature of eukaryotic cells, essential for the exchange of material and information between cytoplasm and nucleoplasm. While, typical eukaryotic cells harbor thousands of NPCs covering the nucleus surface, a quantitative characterization of their spatial distribution remains lacking. Taking advantage of super-resolution microscopy, we imaged and segmented individual NPCs in myoblast cells to reconstruct the nuclear surface. Our spatial statistics analysis of NPCs on the nuclear surface reveals the existence of a 400nm repulsion length between NPCs, likely reflecting the mesh size of the underlying lamin network. Furthermore, we identify three key correlates of NPC density. (1) Myoblast actin fibres, which can indent the nucleus, correlate with a decrease in NPC surface density, contrary to what was reported in previous studies; (2) Regions of the nuclear envelope near large heterochromatin domains exhibit reduced NPC surface density; and (3) There is a non-monotonous relationship between NPC density and the nuclear envelope curvature. This last observation is consistent with the existence of NPC-preferred curvature suggesting curvature sensing properties. In conclusion, this study provides new insights into the spatial distribution of NPCs, shedding light on possible new determinants of NPC spatial distribution.

biophysics↗

bioRxiv2024

Deep learning detection of dynamic exocytosis events in fluorescence TIRF microscopy

Segmentation and detection of biological objects in fluorescence microscopy is of paramount importance in cell imaging. Deep learning approaches have recently shown promise to advance, automatize and accelerate analysis. However, most of the interest has been given to the segmentation of static objects of 2D/3D images whereas the segmentation of dynamic processes obtained from time-lapse acquisitions has been less explored. Here we adapted DeepFinder, a U-net originally designed for 3D noisy cryo-electron tomography (cryo-ET) data, for the detection of rare dynamic exocytosis events (termed ExoDeepFinder) observed in temporal series of 2D Total Internal Reflection Fluorescent Microscopy (TIRFM) images. ExoDeepFinder achieved good absolute performances with a relatively small training dataset of 60 cells/[~]12000 events. We rigorously compared deep learning performances with unsupervised conventional methods from the literature. ExoDeepFinder outcompeted the tested methods, but also exhibited a greater plasticity to the experimental conditions when tested under drug treatments and after changes in cell line or imaged reporter. This robustness to unseen experimental conditions did not require re-training demonstrating generalization capability of ExoDeepFinder. ExoDeepFinder, as well as the annotated training datasets, were made transparent and available through an open-source software as well as a Napari plugin and can directly be applied to custom user data. The apparent plasticity and performances of ExoDeepFinder to detect dynamic events open new opportunities for future deep-learning guided analysis of dynamic processes in live-cell imaging.

bioinformatics↗

bioRxiv2023

Collective directional memory controls the range of epithelial cell migration

Cell migration is a fundamental behavior in multicellular development, regeneration, and homeostasis, which is deregulated in cancer. Epithelial cells migrate individually when isolated and collectively within a tissue. However, how interactions between cells affect their ability to explore space and their sensitivity to guidance signals is poorly understood. We show that isolated cells that are persistent random walkers adopt a super-diffusive behavior in an epithelium. The effect is stronger than external guidance cues and enables cells to reach greater distances than when isolated. This behavior is consistent with a fractional Brownian motion that emerges from velocity coordination between neighboring cells with intact intercellular adhesion. Furthermore, we show how the molecular stability and mechanosensitivity of adhesion complexes, both linked to the ability of the adhesion protein vinculin to dimerize, ultimately regulate the speed of collective migration and the sensitivity to guidance signals. Together, our results show how cell speed, persistence, and directionality define the efficiency of spatial cell exploration on short, intermediate, and long time scales, respectively.

biophysics↗

bioRxiv2023

Peripheral positioning of lysosomes supports melanoma aggressiveness

Emerging evidences suggest that function and position of organelles are pivotal for tumor cell dissemination. Among them, lysosomes stand out as they integrate metabolic sensing with gene regulation and secretion of proteases. Yet, how their function is linked to their position and how this controls metastasis remains elusive. Here, we analyzed lysosome subcellular distribution in patient-derived melanoma cells and patient biopsies and found that lysosome spreading scales with their aggressiveness. Peripheral lysosomes promote matrix degradation and invasion of melanoma cells which is directly linked to their lysosomal and cell transcriptional programs. When controlling lysosomal positioning using chemo-genetical heterodimerization in patient-derived melanoma cells, we demonstrated that perinuclear clustering impairs lysosomal secretion, matrix degradation and invasion. Impairing lysosomal spreading in two distinct in vivo models (mouse and zebrafish) significantly reduces invasive outgrowth. Our study provides a direct demonstration that lysosomal positioning controls cell invasion, illustrating the importance of organelle adaptation in carcinogenesis and suggesting that lysosome positioning could potentially be used for the diagnosis of metastatic melanoma.

cell biology↗

bioRxiv2022

Membrane tension spatially organizes lysosomal exocytosis

Lysosomal exocytosis is involved in many key cellular processes but its spatio-temporal regulation is poorly known. Using total internal reflection fluorescence microscopy (TIRFM) and spatial statistics, we observed that lysosomal exocytosis is not random at the adhesive part of the plasma membrane of RPE1 cells but clustered at different scales. Although the rate of exocytosis is regulated by the actin cytoskeleton, neither interfering with actin or microtubule dynamics by drug treatments alters its spatial organization. Exocytosis events partially co-appear at focal adhesions (FAs) and their clustering is reduced upon removal of FAs. Changes in membrane tension following a hypo-osmotic shock or treatment with methyl-{beta}-cyclodextrin was found to increase clustering. To investigate the link between FAs and membrane tension, cells were cultured on adhesive ring-shaped micropatterns, which allows to control the spatial organization of FAs. By using a combination of TIRFM and fluorescence lifetime imaging microscopy (FLIM) microscopy, we revealed the existence of a radial gradient in membrane tension. By changing the diameter of micropatterned substrates, we further showed that this gradient as well as the extent of exocytosis clustering can be controlled. Together, our data indicate that the spatial clustering of lysosomal exocytosis relies on membrane tension patterning controlled by the spatial organization of FAs.

biophysics↗

bioRxiv2021

Regulation of neuronal progenitor delamination by dynein-driven post-Golgi apical transport

Radial glial (RG) cells are the neural stem cells of the developing neocortex. Apical RG (aRG) cells can delaminate to generate basal RG (bRG) cells, a cell type associated with human brain expansion. Here, we report that this delamination is regulated by the post-Golgi secretory pathway. Using in situ subcellular live imaging, we show that post-Golgi transport of RAB6+ vesicles occurs toward the minus ends of microtubules and depends on dynein. We demonstrate that the apical determinant Crumbs3 (CRB3) is also transported by dynein. Double knockout of RAB6A/A and RAB6B impairs apical localization of CRB3, and induces a retraction of aRG cell apical process, leading to delamination and ectopic division. These defects are phenocopied by knock-out of the dynein activator LIS1. Overall, our results identify a RAB6-dynein-LIS1 complex for Golgi to apical surface transport in aRG cells, and highlights the role of this pathway in the maintenance of neuroepithelial integrity.

cell biology↗