Biology subjects

Cazevieille, C.

Publications and source records attributed to Cazevieille, C..

17 recordsLinked to original sources

bioRxiv2025

Patient induced pluripotent stem cells identify specificities of a reticular pseudodrusen phenotype in age-related macular degeneration

BackgroundAge-related macular degeneration (AMD) is a leading cause of vision loss. Reticular pseudodrusen (RPD), deposits on the apical side of the retinal pigment epithelium (RPE), signify a distinctive and critical AMD phenotype. Yet, their molecular basis and relationship to the conventional drusen seen in AMD remain unclear. ResultsWe generated induced pluripotent stem cell-derived RPE cells from a clinically phenotyped cohort comprising only individuals with conventional drusen (AMD/RPD-) or drusen coexisting with RPD (AMD/RPD+). From these cells, we generated single-cell transcriptomics, proteomics, and functional data to identify differences between the two cohorts. We show that AMD/RPD+ RPE cells exhibit enrichment in extracellular matrix (ECM) remodelling, cytoskeletal, and hypoxia-responsive programs, whereas AMD/RPD- RPE cells display a relatively greater representation of mitochondrial and protein homeostasis pathways. Both subtypes engaged pathways classically linked to ageing, including ECM remodelling and mitochondrial function, but differed in the direction and extent of these changes. Expression and protein quantitative trait loci (QTLs) highlight shared genetic influences on mitochondrial and iron-handling pathways, while disease-interacting eQTLs and transcriptome-wide association study identify regulatory signals that are distinctive of the RPD subtype within AMD, including through regulation of ECM. Functionally, all iPSC-derived RPE formed drusen-like deposits in vitro: AMD/RPD-lines generated more basal deposits, whereas AMD/RPD+ cells exhibited greater structural instability under bisretinoid-induced stress. ConclusionsThese findings indicate that AMD with and without RPD represent mechanistically distinct entities and provide novel insight into the molecular mechanisms underlying disease heterogeneity in AMD.

genetics↗

bioRxiv2025

WFS1E864K in humans and mice causes Wolfram-like syndrome optic atrophy via early axonal mitochondrial dysfunction

Wolfram-like syndrome leads to retinal ganglion cell degeneration and vision loss. Wolfram-like syndrome is primarily caused by variants in the WFS1 gene, which encodes an endoplasmic reticulum resident transmembrane protein, Wolframin. To date, the disease mechanism remains unclear, and no therapies are available. Here, we generated a mouse model carrying the pathogenic WFS1E864K allele that recapitulated key features of human Wolfram-like syndrome, including bilateral optic atrophy, retinal nerve fiber thinning and lamination of the outer plexiform layer. We demonstrated, using the Wfs1E864K mouse model, that alteration of the protein leads to impairments of retinal ganglion cell function, associated with a thinning of the inner retina layer and nerve fibers. These alterations are associated with myelin disorganization, axonal death, mitochondrial alterations in the axons, and impairment of endoplasmic reticulum-mitochondria communication in the soma. Our data showed that primary deficits are localized in the optic nerve before progressing towards the retinal ganglion cell soma. RNAseq analysis identified several altered signaling pathways such as in lipid metabolism, glia activation response, metabolic stress, organelle transport and quality control. These findings highlighted the critical role of Wolframin in optic nerve mitochondrial physiology, providing us with a pertinent model to develop novel innovative therapeutic strategies.

neuroscience↗

bioRxiv2025

Monitoring the dynamics of exosomes through the tracking of Rab7 partners

Extracellular vesicles (EVs) play a crucial role in cell-cell signaling, and their dysregulation is linked to various pathologies. EVs can originate from the plasma membrane as microvesicles, or form within endosomal compartments that fuse with the plasma membrane, releasing their intraluminal vesicles in the extracellular space as exosomes. However, distinguishing between these two types of EVs is challenging due to their common protein markers, necessitating cumbersome isolation methods. To overcome this limitation, we developed an innovative tool using Rab7-mediated proximity labelling and mass spectrometry. This technological advancement enables the covalent labeling of Rab7 partners allowing the tracking of intracellular and extracellular exosomal cargoes.

cell biology↗

bioRxiv2025

Architecture and function of Bud3 and Bud4-induced septin structures

At the time of cytokinesis, a double septin ring is assembled at the division site in many eukaryotic cells. In budding yeast the double ring is made by two arrays of circumferential septin filaments at the two sides of the bud neck, which are thought to compartmentalize the membrane around the cleavage site. Integrity of the double septin ring requires the anillin Bud4 and its presumed partner Bud3, which associate with septins in mitosis and have separate, yet unknown, roles in stabilizing septin circumferential filaments. Through in vitro reconstitution assays using purified proteins, we show that Bud3 and Bud4 organise septin filaments in distinct ways, while together they cooperate to assemble higher-order septin networks. In agreement with their separate roles in septin organization, Bud3 and Bud4 bind to different septins and require septins to associate with each other, indicating that they modulate septin architecture independently but synergistically. We also provide evidence that Bud3 and Bud4 bind membranes in vivo and in vitro, consistent with the presence of lipid-binding domains in their primary sequence. Using bud3 bud4 double mutants that lack the septin double ring, we show that in vivo proteins marking cytokinetic remnants require the double ring to efficiently concentrate at the division site, while other proteins landing at the bud neck at cytokinesis are unaffected. Thus, we propose that a septin double ring may imprint a selective spatial memory for cytokinesis that is transmitted throughout subsequent cell divisions.

cell biology↗

bioRxiv2025

Dengue virus harnesses mosquito Syntenin to load and secrete viral RNA into salivary exosomes

Viruses exploit extracellular vesicles (EVs) to transfer infection-enhancing viral RNAs. However, mechanisms underlying viral RNA loading remain elusive. We leveraged our previous discovery that dengue virus secretes transmission-enhancing subgenomic flaviviral RNA (sfRNA) into mosquito salivary EVs to investigate viral RNA loading mechanism. We demonstrate that sfRNA alone promotes the secretion of sfRNA-containing EVs marked by the mosquito EV biogenesis protein AeSyntenin, by applying microscopy and viral genetic editing in in vitro and in vivo models. SfRNA via its stem loop structures interacts intracellularly with mosquito AeSyntenin and this interaction is selectively maintained within EVs as shown by complementary RNA-affinity chromatography and RNA immunoprecipitation, and AI-based prediction. Finally, we used systemic and salivary gland-specific protein depletion to establish a functional role for mosquito AeSyntenin in exosome production and salivary secretion of sfRNA. We propose that sfRNA binds AeSyntenin to drive its selective packaging and release into exosomes, elucidating a mechanism for viral RNA incorporation into EVs. Significance statementViruses hijack extracellular vesicles (EVs) to enhance viral dissemination, but the mechanisms enabling selective viral RNA packaging into EVs remain unclear. Specifically, dengue virus transmission by mosquitoes relies on EV-based delivery of an immune-inhibitory subgenomic flaviviral RNA (sfRNA). Here, we uncover how dengue virus sfRNA is actively sorted into EVs from mosquito saliva. We show that sfRNA alone induces its secretion via EVs. We discover that sfRNA directly interacts with AeSyntenin intracellularly, and that this interaction persists in secreted EVs. Functional depletion studies reveal AeSyntenins role in salivary EV formation and sfRNA secretion. These findings establish a novel paradigm by which viral RNAs exploit vector EV pathways for dissemination.

microbiology↗

bioRxiv2025

A novel membrane contact site in vestibular hair cells

The mammalian vestibular system has two types of sensory receptor hair cells (HCs), each with different neurotransmission mechanisms. Type II HCs use ribbon synapses to transmit neurotransmitters like glutamate to afferent neurons. On the other hand, type I HCs are nearly engulfed by a calyceal afferent ending and also form ribbon synapses. These HCs regulate afferent activity through non-quantal transmission (NQT), which is faster than classic neurotransmitter release and may play a key role in stabilizing vision and balance during rapid head movements. Here, we describe a novel striated contact, present between the mouse type I HC and its calyceal afferent ending, and intimately associated with atypical plasma membrane-apposed (PMA) mitochondria. This distinctive arrangement has the potential to serve or modulate NQT.

neuroscience↗

bioRxiv2024

Septin filament assembly assists the lateral organization of membranes

Compartmentalized interactions of plasma membrane components are essential to support many cell functions, from signaling to cell division, adhesion, migration, or phagocytosis. Cytoskeletal-membrane interactions play an important role in forming membrane compartments, and this feature has been primarily studied through the actin cytoskeleton. Unlike actin, septins directly interact with membranes, acting as scaffolds to recruit proteins to specific cellular locations and as structural diffusion barriers for membrane components. However, how septins interact with and remodel the local membrane environment is unclear. Here we combined minimal reconstituted systems based on fluorescence microscopy and quantitative atomic force microscopy together with live yeast cell imaging and STED microscopy to study septin-mediated membrane organization. Our results show that septins self-assembly into filament-based sub-micrometric patches and high-order structures prompt their membrane-organizing role in vitro and in yeast cells, respectively. Furthermore, we show that the polybasic domain of Cdc11, in addition to the amphipathic helix of Cdc12, plays an essential role in supporting the membrane remodeling and curvature-sensing properties of yeast septins. Collectively, our work provides a framework for understanding the molecular mechanisms by which septins can support cellular functions intimately linked to membranes.

cell biology↗

bioRxiv2024

The multifunction Coxiella effector Vice stimulates macropinocytosis and interferes with the ESCRT machinery

Intracellular bacterial pathogens divert multiple cellular pathways to establish their niche and persist inside their host. Coxiella burnetii, the causative agent of Q fever, secretes bacterial effector proteins via its Type 4 secretion system to generate a Coxiella-containing vacuole (CCV). Manipulation of lipid and protein trafficking by these effectors is essential for bacterial replication and virulence. Here, we have characterized the lipid composition of CCVs and discovered that the effector Vice interacts with phosphoinositides and membranes enriched in phosphatidylserine (PS) and lysobisphosphatidic acid (LBPA). Remarkably, eukaryotic cells ectopically expressing Vice present compartments that resemble early CCVs in both morphology and composition. We discovered that the biogenesis of these compartments relies on the double function of Vice. The effector protein initially localizes at the plasma membrane of eukaryotic cells where it triggers the internalization of large vacuoles by macropinocytosis. Then, Vice stabilizes these compartments by perturbing the ESCRT machinery and inhibiting the formation of intraluminal vesicles (ILVs). Collectively, our results reveal that Vice is an essential C. burnetii effector protein capable of hijacking two major cellular pathways to shape the bacterial replicative niche. Significance statementCoxiella burnetii is a unique bacterial pathogen that secretes more than a hundred effector proteins to manipulate cellular processes and establish a replicative niche, the Coxiella-containing vacuole (CCV). Our study identified host cell lipids that are actively recruited by the bacterium to the CCV. Using a library of effector mutants, we identified the protein Vice (for Vacuole-inducing Coxiella effector) as the first bacterial effector capable of interacting with lysobisphosphatydic acid-enriched membranes and accumulating this lipid to CCVs. We show that Vice is also capable of stimulating macropinocytosis and inhibiting the ESCRT machinery. Together, our data show how a single bacterial effector can manipulate different cellular processes to favor the biogenesis of a bacterial pathogens niche.

microbiology↗

bioRxiv2023

The Wolfram-like variant WFS1E864K destabilizes MAM and compromises autophagy and mitophagy in human and mice.

Dominant variants in WFS1, a gene coding for the mitochondria-associated endoplasmic reticulum (ER) membrane (MAM) resident protein Wolframin, have been associated with Wolfram-like syndrome (WLS). In vitro and in vivo, WFS1 loss results in reduced ER to mitochondria calcium (Ca2+) transfer, mitochondrial dysfunction, and enhanced autophagy and mitophagy. However, in WLS pathological context, whether the mutant protein triggers the same cellular processes is unknown. Here, we show that, in human fibroblasts and murine neuronal cultures, WLS protein WFS1E864K leads to decreases in mitochondria bioenergetics and Ca2+ uptake, deregulation of the mitochondrial quality system mechanisms, and alteration of the autophagic flux. Moreover, in the Wfs1E864K mouse, these alterations are concomitant with a decrease of MAM number. These findings reveal pathophysiological similarities between WS and WLS, highlighting the importance of WFS1 for MAMs integrity and functionality. It may open new treatment perspectives, until now non-existent, for patients with WLS.

neuroscience↗

bioRxiv2023

A comparative ultrastructure study of the tardigrade Ramazzottius varieornatus in the hydrated state, after desiccation and during the process of rehydration.

Tardigrades can survive hostile environments such as desiccation by adopting a state of anhydrobiosis. Numerous tardigrade species have been described thus far, and recent genome and transcriptome analyses revealed that several distinct strategies were employed to cope with harsh environments depending on the evolutionary lineages. Detailed analyses at the cellular and subcellular levels are essential to complete these data. In this work, we analyzed a tardigrade species that can withstand rapid dehydration, Ramazzottius varieornatus. Surprisingly, we noted an absence of the anhydrobiotic-specific extracellular structure previously described for the Hypsibius exemplaris species. Both Ramazzottius varieornatus and Hypsibius exemplaris belong to the same evolutionary class of Eutardigrada. Nevertheless, our observations reveal discrepancies in the anhydrobiosis mechanisms between these two species. Interestingly, these discrepancies are correlated with their variations in dehydration resistance.

cell biology↗

bioRxiv2022

The aminoglycoside streptomycin triggers ferroptosis in tumor initiating cells

Compelling evidence suggests that tumor initiating cells (TIC) are the roots of current shortcomings in advanced and metastatic cancer treatment. TIC represents a minor subpopulation of tumor cells endowed with self-renewal and multi-lineage differentiation capacity, which can disseminate and seed metastasis in distant organ. Our work identified Streptomycin (SM), a potent bactericidal antibiotic, as a new molecule capable of targeting non-adherent TIC from colon and breast cancer cell lines by inducing mitochondrial-dependent ferroptosis. SM-induced ferroptosis associates with profound alterations in mitochondrial morphology, such as swelling and cristae enlargement, coupled with hyperpolarization of mitochondrial membrane potential and production of mitochondrial ROS. The peculiar SM structure, and more particularly its aldehyde group, is essential for this mechanism. As such, the mere reduction of SM into dihydrostreptomycin abolishes its effect on TIC. This study reveals a new mechanism of action of SM that could help comprehend the molecular basis of TIC adaptation to inhospitable environments and pave the way for new treatment of advanced cancers.

cancer biology↗

bioRxiv2022

LIX1 controls digestive mesenchyme-derived cell fate decision by regulating cristae organization in mitochondria

Limb Expression 1 (LIX1) is a master regulator of digestive mesenchymal progenitor and GastroIntestinal Stromal Tumor (GIST) cell proliferation by controlling the expression of the Hippo effectors YAP1/TAZ and KIT. However, the underlying mechanisms of these LIX1-mediated regulations and tumor promotion remain to be elucidated. Here, we report that LIX1 is S-palmitoylated on cysteine 84 and localized in mitochondria. LIX1 knock-down affects the mitochondrial ultrastructure, resulting in decreased respiration and mitochondrial reactive oxygen species production. This is sufficient to downregulate YAP1/TAZ and reprogram KIT-positive GIST cells towards the smooth muscle cell lineage with reduced proliferative and invasive capacities. Mechanistically, LIX1 knock-down impairs the stability of the mitochondrial proteins PHB2 and OPA1 that are found in complexes with mitochondrial-specific phospholipids and are required for cristae organization. Supplementation with unsaturated fatty acids counteracts the effects of LIX1 knock-down on mitochondrial morphology and ultrastructure, restores YAP1/TAZ signaling, and consequently KIT levels. Altogether, our findings demonstrate that LIX1 contributes to GIST aggressive potential by modulating YAP1/TAZ and KIT levels, a process that depends on mitochondrial remodeling. Our work brings new insights into the mechanisms that could be targeted in tumors in which YAP1 and TAZ are implicated.

cancer biology↗

bioRxiv2021

Meisosomes, folded membrane platforms, link the epidermis to the cuticle in C. elegans

Apical extracellular matrices (aECMs) form a physical barrier to the environment. In C. elegans, the epidermal aECM, the cuticle, is composed mainly of different types of collagen, associated in circumferential ridges separated by furrows. Here, we show that in mutants lacking furrows, the normal intimate connection between the epidermis and the cuticle is lost, specifically at the lateral epidermis, where, in contrast to the dorsal and ventral epidermis, there are no hemidesmosomes. At the ultrastructural level, there is a profound alteration of structures that we term "meisosomes", in reference to eisosomes in yeast. We show that meisosomes are composed of stacked parallel folds of the epidermal plasma membrane, alternately filled with cuticle. We propose that just as hemidesmosomes connect the dorsal and ventral epidermis, above the muscles, to the cuticle, meisosomes connect the lateral epidermis to it. Moreover, furrow mutants present marked modifications of the biomechanical properties of their skin and exhibit a constitutive damage response in the epidermis. As meisosomes co-localise to macrodomains enriched in phosphatidylinositol (4,5) bisphosphate, they might act, like eisosomes, as signalling platforms, to relay tensile information from the aECM to the underlying epidermis, as part of an integrated stress response to damage.

cell biology↗

bioRxiv2020

Differentiation of human induced pluripotent stem cells into functional airway epithelium

RationaleHighly reproducible in vitro generation of human bronchial epithelium from pluripotent stem cells is an unmet key goal for drug screening to treat lung diseases. The possibility of using induced pluripotent stem cells (hiPSC) to model normal and diseased tissue in vitro from a simple blood sample will reshape drug discovery for chronic lung, monogenic and infectious diseases. MethodsWe devised a simple and reliable method that drives a blood sample reprogrammed into hiPSC subsequently differentiated within 45 days into air-liquid interface bronchial epithelium (iALI), through key developmental stages, definitive-endoderm (DE) and Ventralized-Anterior-Foregut-Endoderm (vAFE) cells. ResultsReprogramming blood cells from one healthy and 3 COPD patients, and from skin-derived fibroblasts obtained in one PCD patient, succeeded in 100% of samples using Sendai viruses. Mean cell purity at DE and vAFE stages was greater than 80%, assessed by expression of CXCR4 and NKX2.1, avoiding the need of cell sorting. When transferred to ALI conditions, vAFE cells reliably differentiated within 4 weeks into bronchial epithelium with large zones covered by beating ciliated, basal, goblets, club cells and neuroendocrine cells as found in vivo. Benchmarking all culture conditions including hiPSCs adaptation to single-cell passaging, cell density and differentiation induction timing allowed for consistently producing iALI bronchial epithelium from the five hiPSC lines. ConclusionsReliable reprogramming and differentiation of blood-derived hiPSCs into mature and functional iALI bronchial epithelium is ready for wider use and this will allow better understanding lung disease pathogenesis and accelerating the development of novel gene therapies and drug discovery.

bioengineering↗

bioRxiv2020

Neuromotor impairment, hearing loss and blindness in a preclinical mouse model of Charcot Marie-Tooth disorder

Schwann cells produce myelin sheath around peripheral nerve axons. Myelination is critical for rapid propagation of action potentials, as illustrated by the large number of acquired and hereditary peripheral neuropathies, such as diabetic neuropathy or Charcot-Marie-Tooth (CMT) diseases, that are commonly associated with a process of demyelination. Peripheral neuropathy is a major complication of diabetes, and the pathomechanism of the disease remains poorly studied. Here, we studied the progressive demyelinating process, hearing impairment and blindness observed in the CMT1A mouse model C3. Our results confirm that these mice represent a robust and validated model to study the peripheral neuropathy induced by CMT disorder allowing to determine the efficacy of new pharmacological candidates targeting demyelinating diseases such as CMT1A disorder.

neuroscience↗

bioRxiv2018

Microbial predator-prey interactions could favor coincidental selection of diverse virulence factors in marine coastal waters.

Vibrios are ubiquitous in marine environments and opportunistically colonize a broad range of hosts. Strains of Vibrio tasmaniensis present in oyster farms can thrive in oysters during juvenile mortality events. Among them, V. tasmaniensis LGP32 behaves as a facultative intracellular pathogen of oyster hemocytes, a property rather unusual in vibrios. Herein, we asked whether LGP32 resistance to phagocytosis could result from coincidental selection of virulence factors during interactions with heterotrophic protists, such as amoeba, in the environment. To answer that question, we developed an integrative study, from the first description of amoeba diversity in oyster-farming areas to the characterization of LGP32 interactions with amoebae of the Vannella genus that were found abundant in the oyster environment. LGP32 was shown to be resistant to grazing by amoebae and this phenotype was dependent on previously identified virulence factors: the secreted metalloprotease Vsm and the copper efflux p-ATPase CopA. Using dedicated in vitro assays, our results showed that these virulence factors act at different steps during amoeba-vibrio interactions than they do in oysters-vibrio interactions. Hence, the virulence factors of LGP32 are key determinants of biotic interactions with multiple hosts ranging from protozoans to metazoans, suggesting that the selective pressure exerted by amoebae in marine coastal environments favor coincidental selection of virulence factors.

microbiology↗

bioRxiv2018

Wolbachia endosymbionts subvert the endoplasmic reticulum to acquire host membranes without triggering ER stress

The reproductive parasite Wolbachia are the most common endosymbionts on earth, present in a plethora of arthropod species. They have been introduced into mosquitos to successfully prevent the spread of vector-borne diseases, yet the strategies of host cell subversion underlying their obligate intracellular lifestyle remain to be explored in depth in order to gain insights into the mechanisms of pathogen-blocking. Like some other intracellular bacteria, Wolbachia reside in a host-derived vacuole in order to replicate and escape the immune surveillance. Using here the pathogen-blocking Wolbachia strain from Drosophila melanogaster, introduced into two different Drosophila cell lines, we show that Wolbachia subvert the endoplasmic reticulum to acquire their vacuolar membrane and colonize the host cell at high density. Wolbachia redistribute the endoplasmic reticulum to increase contact sites, and time lapse experiments reveal tight coupled dynamics suggesting important signalling events or nutrient uptake. They however do not affect the tubular or cisternal morphologies. A fraction of endoplasmic reticulum becomes clustered, allowing the endosymbionts to reside in between the endoplasmic reticulum and the Golgi apparatus, possibly modulating the traffic between these two organelles. Gene expression analyses and immunostaining studies suggest that Wolbachia achieve persistent infections at very high titers without triggering endoplasmic reticulum stress or enhanced ERAD-driven proteolysis, suggesting that amino acid salvage is achieved through modulation of other signalling pathways.\n\nAuthor summaryWolbachia are a genus of intracellular bacteria living in symbiosis with millions of arthropod species. They have the ability to block the transmission of arboviruses when introduced into mosquito vectors, by interfering with the cellular resources exploited by these viruses. Despite the biomedical interest of this symbiosis, little is known about the mechanisms by which Wolbachia survive and replicate in the host cell. We show here that the membrane composing the Wolbachia vacuole is acquired from the endoplasmic reticulum, a central organelle required for protein and lipid synthesis, and from which originates a vesicular trafficking toward the Golgi apparatus and the secretory pathway. Wolbachia modify the distribution of this organelle to increase their interactions with this source of membrane and likely of nutrients as well. In contrast to some intracellular pathogenic bacteria, the effect of Wolbachia on the cell homeostasis does not induce a stress on the endoplasmic reticulum. One of the consequences of such a stress would be an increased proteolysis used to relieve the cell from an excess of misfolded proteins. Incidentally, this shows that Wolbachia do not acquire amino acids from the host cell through this strategy.

cell biology↗