Biology subjects

Banterle, N.

Publications and source records attributed to Banterle, N..

8 recordsLinked to original sources

bioRxiv2026

Lack of centrosomes limits the epithelial-to-mesenchymal transition in human mammary cells

As the main microtubule network organisers of animal cells, centrosomes orchestrate diverse cellular processes. Centrosomes have been linked to cancer when numerically or structurally aberrant, yet their precise roles at different cancer stages remains to be defined. Here, we study centrosome function in the epithelial-to-mesenchymal transition (EMT), a key driver of cancer initiation, progression and metastasis. We first depleted centrosomes in a breast cancer mesenchymal-like model, resulting in insignificant cellular or nuclear rearrangements. We then investigated non-carcinogenic breast cells undergoing the EMT via TGF{beta} signalling, and removed the centrosomes before triggering this transition. Stimulated epithelial cells acquired a mesenchymal phenotype and rearranged their cytoskeleton. By contrast, stimulated cells lacking centrosomes retained epithelial morphology, showed little cytoskeletal remodelling, yet still altered nuclear shape and upregulated key EMT markers. Transcriptome analysis revealed reduced expression of important genes involved in extracellular matrix organisation and a downregulation of cell junction components when lacking centrosomes; further analysis revealed paxillin showing reduced colocalisation with actin focal adhesions. Centrosomes thus prove essential for cytoskeletal remodelling in the EMT of breast cancer cells.

cell biology↗

bioRxiv2026

Regulated conformational transitions in seipin define a functional ER–lipid droplet interface

Lipid droplets (LDs) are key organelles in cellular lipid homeostasis that form at the endoplasmic reticulum (ER) through a sequence of membrane rearrangements. While seipin emerged as an essential protein complex for LD biogenesis, how seipin-mediated LD formation proceeds beyond the initial step of neutral lipid nucleation remains unknown. Using a combination of in vitro and in-cell cryogenic electron microscopy (cryo-EM), ultrastructural expansion microscopy, molecular simulations and tailored genetic perturbations, we show that the seipin transmembrane domains undergo large-scale conformational rearrangements that define the architecture of the ER-LD interface and enable LD growth. Cryo-EM of purified Xenopus seipin revealed coexistence of two states: a compact "closed" conformation, consistent with early LD biogenesis, and an "open" conformation in which the transmembrane helices splay out laterally. Molecular dynamics simulations indicate that this open state induces local membrane curvature and promotes triacylglycerol accumulation. We identify conserved flexible linkers between the seipin luminal and transmembrane regions that act as mechanical hinges, enabling this conformational transition. We demonstrate that mutations in these hinge regions hinder seipin opening and affect LD formation in yeast and human cells. Analysis of native ER-LD contacts in human cells using light microscopy and cryo-electron tomography confirms that the seipin complex opens to establish stereotypical ~21-nm necks connecting the ER bilayer and LD monolayer. Moreover, we identify the liver-enriched microprotein SMLR1 as an inhibitor of this seipin conformational transition, providing a regulatory mechanism for seipin-dependent lipid storage in a tissue-specific manner. Together, these data establish seipin opening as a key structural rearrangement at the ER-LD interface that is essential for LD biogenesis and growth.

Cell Biology↗

bioRxiv2026

Septin-mediated coupling of protein import and division during chloroplast evolution

Chloroplast biogenesis depends on both protein import and organelle division, yet how their coordination emerged during evolution remains unclear. Here, we show that the single septin SEP1 links these pathways in the green alga Chlamydomonas reinhardtii. SEP1 forms a filamentous network on the chloroplast envelope during interphase and reorganizes into a ring at the chloroplast division site during cytokinesis. Loss of SEP1 selectively impairs import of chloroplast-division proteins and causes mispositioning of the division ring, without impairing bulk chloroplast protein import. SEP1 physically associates with outer-envelope TOC GTPases through evolutionarily related GTPase domains. Phylogenetic analysis places TOC GTPases within an algal septin-derived clade, and heterologous expression of SEP1 in land plants, in which septins are absent, shows conservation of its chloroplast targeting and TOC binding. Together, these findings identify septins as coordinators of plastid protein import and division and suggest that this coupling emerged early in chloroplast evolution.

cell biology↗

bioRxiv2025

Microscopy Nodes: versatile 3D microscopy visualization with Blender

Effective visualization of 3D microscopy data is essential for communicating biological results. While scientific 3D rendering software is specifically designed for this purpose, it often lacks the flexibility found in non-scientific software like Blender, which is a free and open-source 3D graphics platform. However, loading microscopy data in Blender is not trivial. To bridge this gap, we introduce Microscopy Nodes, an extension for Blender that enables the seamless integration of large microscopy data. Microscopy Nodes provides efficient loading and visualization of up to 5D microscopy data from Tif and OME-Zarr files. Microscopy Nodes supports various visualization modes including volumetric, isosurface, and label-mask representations, and offers additional tools for slicing, annotation, and dynamic adjustments. By leveraging Blenders advanced rendering capabilities, users can create high-quality visualizations that accommodate both light and electron microscopy. Microscopy Nodes makes powerful, clear data visualization available to all researchers, regardless of their computational experience, and is available through the Blender extensions platform with comprehensive tutorials.

cell biology↗

bioRxiv2022

Grand canonical Brownian dynamics simulations of adsorption and self-assembly of SAS-6 rings on a surface

The protein SAS-6 forms dimers, which then self-assemble into rings that are critical for the nine-fold symmetry of the centriole organelle. It has recently been shown experimentally that the self-assembly of SAS-6 rings is strongly facilitated on a surface, shifting the reaction equilibrium by four orders of magnitude compared to the bulk. Moreover, a fraction of non-canonical symmetries (i.e., different from nine) was observed. In order to understand which aspects of the system are relevant to ensure efficient self-assembly and selection of the nine-fold symmetry, we have performed Brownian dynamics computer simulation with patchy particles and then compared our results with experimental ones. Adsorption onto the surface was simulated by a Grand Canonical Monte Carlo procedure and Random Sequential Adsorption kinetics. Furthermore, self-assembly was described by Langevin equations with hydrodynamic mobility matrices. We find that as long as the interaction energies are weak, the assembly kinetics can be described well by the coagulation-fragmentation equations in the reaction-limited approximation. By contrast, larger interaction energies lead to kinetic trapping and diffusion-limited assembly. We find that selection of nine-fold symmetry requires a small value for the angular interaction range. These predictions are confirmed by the experimentally observed reaction constant and angle fluctuations. Overall, our simulations suggest that the SAS-6 system works at the crossover between a relatively weak binding energy that avoids kinetic trapping and a small angular range that favors the nine-fold symmetry.

biophysics↗

bioRxiv2020

Surface-catalyzed SAS-6 self-assembly directs centriole formation through kinetic and structural mechanisms

Discovering the physical principles directing organelle assembly is a fundamental pursuit in biology. Centrioles are evolutionarily conserved organelles with a 9-fold rotational symmetry of chiral microtubules imparted onto the cilia they template1. Centriole assemble from likewise symmetrical ring polymers of SAS-6 proteins, orthogonal to a toroidal surface surrounding the resident centriole2-4. How surface properties ensure ring assembly with proper symmetry and orthogonal arrangement is not known. Here, we deployed photothermally-actuated off-resonance tapping high-speed atomic force microscopy (PORT-HS-AFM) to decipher physical principles of surface-guided SAS-6 self-assembly. Using machine learning to quantify the polymerization reaction and developing a coagulation-fragmentation model, we discovered that the surface shifts the reaction equilibrium by [~]104 compared to the solution situation, explaining orthogonal organelle emergence. Moreover, molecular dynamics and PORT-HS-AFM revealed that the surface converts helical SAS-6 polymers into 9-fold ring polymers with residual asymmetry, which may impart chiral features to centrioles and cilia. Overall, we discovered two fundamental physical principles directing robust centriole organelle assembly.

biophysics↗

bioRxiv2020

Homogeneous multifocal excitation for high-throughput super-resolution imaging

Super-resolution microscopies, which allow features below the diffraction limit to be resolved, have become an established tool in biological research. However, imaging throughput remains a major bottleneck in using them for quantitative biology, which requires large datasets to overcome the noise of the imaging itself and to capture the variability inherent to biological processes. Here, we develop a multi-focal flat illumination for field independent imaging (mfFIFI) module, and integrate it into an instant structured illumination microscope (iSIM). Our instrument extends the field of view (FOV) to >100x100 {micro}m2 without compromising image quality, and maintains high-speed (100 Hz), multi-color, volumetric imaging at double the diffraction-limited resolution. We further extend the effective FOV by stitching multiple adjacent images together to perform fast live-cell super-resolution imaging of dozens of cells. Finally, we combine our flat-fielded iSIM setup with ultrastructure expansion microscopy (U-ExM) to collect 3D images of hundreds of centrioles in human cells, as well as of thousands of purified Chlamydomonas reinhardtii centrioles per hour at an effective resolution of [~]35 nm. We apply classification and particle averaging to these large datasets, allowing us to map the 3D organization of post-translational modifications of centriolar microtubules, revealing differences in their coverage and positioning.

biophysics↗

bioRxiv2018

Multicolor single particle reconstruction of protein complexes

Single-particle reconstruction (SPR) from electron microscopy images is widely used in structural biology, but lacks direct information on protein identity. To address this limitation, we developed a computational and analytical framework that reconstructs and co-aligns multiple proteins from 2D super-resolution fluorescence images. We demonstrate our method by generating multi-color 3D reconstructions of several proteins within the human centriole and procentriole, revealing their relative locations, dimensions and orientations.

cell biology↗