Biology subjects

Reymond, L.

Publications and source records attributed to Reymond, L..

12 recordsLinked to original sources

bioRxiv2026

A biochemical probe for microtubule lattice integrity uncovers motor-caused lattice damage

Microtubules experience mechanical and enzymatic stresses that can compromise lattice integrity, yet where and how lattice damage forms remains poorly understood due to the lack of tools that directly visualize damage as it occurs. Existing approaches infer damage indirectly through repair events or rely on static ultrastructural snapshots, precluding dynamic analysis. Here, we introduce MT-DS (Microtubule Damage Sensor), a damage-selective fluorescent probe that directly labels microtubule lattice openings. MT-DS combines taxane-based microtubule binding with a multivalent protein scaffold to restrict intraluminal diffusion and selectively retain the probe at sites of lattice openings. Using MT-DS, we visualize intrinsic lattice defects in stabilized microtubules, uncover a strong enrichment of damage at annealing sites, and demonstrate that kinesin-1{Delta}6 actively generates de novo lattice damage during motility. By enabling direct, time-resolved detection of microtubule damage, MT-DS establishes lattice integrity as an experimentally accessible parameter and provides a chemical tool to investigate how mechanical stress reshapes the microtubule cytoskeleton.

biochemistry↗

bioRxiv2025

HAK-actin, U-ExM-compatible probe to image the actin cytoskeleton

Expansion microscopy (ExM) enables super-resolution imaging by physically enlarging biological samples. While ExM has been successfully applied to study the intracellular microtubule cytoskeleton, reliable probes for visualizing actin fibers remain limited. Here, we present HAK-actin, an engineered actin probe compatible with post-labeling Ultrastructure Expansion Microscopy (U-ExM). We show that HAK-actin delivers robust and uniform actin staining across diverse systems, including human cells, microbial eukaryotes, and mouse retinal tissue. This tool provides a simple, versatile, and reproducible solution for actin cytoskeleton visualization, addressing a critical need in cell biology.

cell biology↗

bioRxiv2025

Targeting RhoA activity rejuvenates aged hematopoietic stem cells

Biomechanical alterations contribute to the decreased regenerative capacity of hematopoietic stem cells (HSCs) upon aging. RhoA is a key regulator of mechano-signaling but its role for mechanotransduction in stem cell aging has not been investigated yet. Here, we show that murine HSCs respond to increased nuclear envelope (NE) tension by inducing NE translocation of P-cPLA2, which cell intrinsically activates RhoA. Interestingly, aged HSCs experience physiologically higher intrinsic NE tension, associated with increased NE P-cPLA2 and RhoA activity. Reducing RhoA activity lowers NE tension in aged HSCs. Feature image analysis of HSC nuclei reveals that chromatin remodeling is associated to RhoA inhibition, which includes the restoration of youthful levels of the heterochromatin marker H3K9me2 and a decrease in chromatin accessibility and transcription at retrotransposons. Eventually, we demonstrate that RhoA inhibition upregulates Klf4 expression and transcriptional activity, improving aged HSCs regenerative capacity and lympho/myeloid skewing in vivo. Overall, our data support that an intrinsic mechano-signaling axis dependent on RhoA can be pharmacologically targeted to rejuvenate stem cell function upon aging.

cell biology↗

bioRxiv2025

A silicon rhodamine-fused glibenclamide to label and detect malaria-infected red blood cells

The malaria parasite Plasmodium falciparum affects the lives of millions of people worldwide every year. The detection of replicating parasites within human red blood cells is of paramount importance, requiring appropriate diagnostic tools. Herein, we design and apply a silicon rhodamine-fused glibenclamide (SiR-glib). We first test this far-red fluorescent, fluorogenic and endoplasmic reticulum-targeting sulfonylurea in mammalian cells and pancreatic tissues, before characterizing its labeling performance in red blood cells infected with the asexual developmental stages of Plasmodium falciparum. We further combine SiR-glib with a portable smartphone-based microscope to easily and rapidly identify parasitized red blood cells, providing proof of principle for diagnostic use in rural endemic areas without major healthcare facilities.

biochemistry↗

bioRxiv2024

Targeting protein-ligand neosurfaces using a generalizable deep learning approach

Molecular recognition events between proteins drive biological processes in living systems. However, higher levels of mechanistic regulation have emerged, where protein-protein interactions are conditioned to small molecules. Here, we present a computational strategy for the design of proteins that target neosurfaces, i.e. surfaces arising from protein-ligand complexes. To do so, we leveraged a deep learning approach based on learned molecular surface representations and experimentally validated binders against three drug-bound protein complexes. Remarkably, surface fingerprints trained only on proteins can be applied to neosurfaces emerging from small molecules, serving as a powerful demonstration of generalizability that is uncommon in deep learning approaches. The designed chemically-induced protein interactions hold the potential to expand the sensing repertoire and the assembly of new synthetic pathways in engineered cells.

biochemistry↗

bioRxiv2024

Gentle rhodamines for live-cell fluorescence microscopy

Rhodamines have been continuously optimized in brightness, biocompatibility, and colors to fulfill the demands of modern bioimaging. However, the problem of phototoxicity caused by the excited fluorophore under long-term illumination has been largely neglected, hampering their use in time-lapse imaging. Here we introduce cyclooctatetraene (COT) conjugated rhodamines that span the visible spectrum and exhibit significantly reduced phototoxicity. We identified a general strategy for the generation of Gentle Rhodamines, which preserved their outstanding spectroscopic properties and cell permeability while showing an efficient reduction of singlet-oxygen formation and diminished cellular photodamage. Paradoxically, their photobleaching kinetics do not go hand in hand with reduced phototoxicity. By combining COT-conjugated spirocyclization motifs with targeting moieties, these gentle rhodamines compose a toolkit for time-lapse imaging of mitochondria, DNA, and actin and synergize with covalent and exchangeable HaloTag labeling of cellular proteins with less photodamage than their commonly used precursors. Taken together, the Gentle Rhodamines generally offer alleviated phototoxicity and allow advanced video recording applications, including voltage imaging.

cell biology↗

bioRxiv2022

Tubulin engineering by semisynthesis reveals that polyglutamylation directs detyrosination

Microtubules, a critical component of the cytoskeleton, carry combinations of post-translational modifications (PTMs), which are critical for the regulation of key cellular processes. Long-lived microtubules, in neurons particularly, exhibit both detyrosination of -tubulin as well as polyglutamylation. Dysregulation of these PTMs results in disease, including developmental defects and neurodegeneration. Despite their importance, the mechanisms governing the emergence of such PTM patterns are not well understood, mostly because tools to dissect the function and regulation of tubulin PTMs have been lacking. Here, we report a chemical method to produce fully functional tubulin carrying precisely defined PTMs within its C-terminal tail. Using a sortase- and intein-mediated tandem transamidation strategy, we ligate synthetic -tubulin tails, which are site-specifically glutamylated to specific extents, to recombinant human tubulin heterodimers. Using microtubules reconstituted with such designer tubulins, we show that polyglutamylation of -tubulin promotes its detyrosination by enhancing the activity of the tubulin tyrosine carboxypeptidase vasohibin/SVBP in a manner dependent on the length of polyglutamyl chains. Moreover, modulating polyglutamylation levels in cells results in corresponding changes in detyrosination. Together, using synthetic chemistry to produce tubulins carrying defined PTMs, we can directly link the detyrosination cycle to polyglutamylation, connecting two key regulatory systems that control tubulin function.

biochemistry↗

bioRxiv2022

Advected percolation in the actomyosin cortex drives amoeboid cell motility

Spontaneous locomotion is a common feature of most metazoan cells, generally attributed to the fundamental properties of the actomyosin network. This force-producing machinery has been studied down to the most minute molecular details, especially in lamellipodium-driven migration. Nevertheless, how actomyosin networks work inside contraction-driven amoeboid cells still lacks unifying principles. Here, using stable motile blebs as a model amoeboid motile system, we image the dynamics of the actin cortex at the single filament level and reveal the co-existence of three phases of the actin network with distinct rheological properties. Physical modelling shows that these three phases organize spontaneously due to a rigidity percolation transition combined with an active advection of the percolated network. This spontaneous spatial organization of the mechanical properties of the actin network, which we propose to call advected percolation, constitutes a minimal and generic locomotion mechanism. It explains, down to the single actin filament level and up to the scale of the entire cell, how amoeboid cells can propel efficiently through complex 3D environments, a feature shared by immune and cancer cells.

biophysics↗

bioRxiv2020

Receptor-linked environment-sensitive probe monitors the local membrane environment surrounding the insulin receptor

Functional membrane proteins in the plasma membrane are suggested to have specific membrane environments that play important roles to maintain and regulate the function of proteins. However, the local membrane environments of membrane proteins remain largely unexplored due to the lack of techniques allowing to monitor them in living cells. We have developed a method to probe the local membrane environment surrounding a membrane protein in the plasma membrane by covalently tethering a solvatochromic, environment-sensitive dye, Nile red, to a membrane protein via a flexible linker. Our direct imaging reported on the spatio-temporal properties of membrane fluidity of the local environment surrounding the insulin receptor. The local environment was distinct from the average plasma membrane fluidity and was quite dynamic and heterogeneous. Upon addition of insulin, the local membrane environment surrounding the receptor increased in fluidity in an insulin receptor-kinase dependent manner. This new technology should allow researchers to examine changes in membrane properties caused by receptor activation and devise ways to address the role of these changes in physiological processes.

cell biology↗

bioRxiv2019

Photoactivation of silicon rhodamines via a light-induced protonation

We present a new type of photoactivatable fluorophore that forms a bright silicon rhodamine derivative through a light-dependent isomerization followed by protonation. In contrast to other photoactivatable fluorophores, no caging groups are required, nor are there any undesired side-products released. Using this photoactivatable fluorophore, we created probes for HaloTag and actin for live-cell single-molecule localization microscopy and single-particle tracking experiments. The unusual mechanism of photoactivation and the fluorophores outstanding spectroscopic properties make it a powerful tool for live-cell super-resolution microscopy.

biophysics↗

bioRxiv2018

A chemogenetic approach for optical monitoring of voltage in neurons

Optical monitoring of neuronal voltage using fluorescent indicators is a powerful approach for interrogation of the cellular and molecular logic of the nervous system. Here we describe a Semisynthetic Tethered Voltage Indicator (STeVI1) based upon Nile Red that displays voltage sensitivity when genetically targeted to neuronal membranes. This environmentally sensitive probe allows for wash-free imaging and faithfully detects supra- and subthreshold activity in neurons.

neuroscience↗

bioRxiv2017

Control of mechanical pain hypersensitivity through ligand-targeted photoablation of TrkB positive sensory neurons

SummaryMechanical allodynia is a major symptom of neuropathic pain whereby innocuous touch evokes severe pain. Here we identify a population of peripheral sensory neurons expressing TrkB that are both necessary and sufficient for producing pain from light touch after nerve injury. Mice in which TrkB-Cre expressing neurons are ablated are less sensitive to the lightest touch under basal conditions, and fail to develop mechanical allodynia in a model of neuropathic pain. Moreover, selective optogenetic activation of these neurons after nerve injury evokes marked nociceptive behavior. Using a phototherapeutic approach based upon BDNF, the ligand for TrkB, we perform molecule-guided laser ablation of these neurons and achieve long-term retraction of TrkB positive neurons from the skin and pronounced reversal of mechanical allodynia across multiple types of neuropathic pain. Thus we identify the peripheral neurons which transmit pain from light touch and uncover a novel pharmacological strategy for its treatment.\n\nHighlightsO_LITrkB+ neurons detect light touch under basal conditions\nC_LIO_LITrkB+ neurons convey mechanical allodynia in neuropathic pain states\nC_LIO_LIA photosensitizing derivative of BDNF allows for photoablation of TrkB+ neurons\nC_LIO_LIBDNF-guided photoablation reverses allodynia in multiple types of neuropathic pain\nC_LI

neuroscience↗