Biology subjects

Brunet, M.

Publications and source records attributed to Brunet, M..

10 recordsLinked to original sources

bioRxiv2026

Systematic comparison of gliflozins identifies a selective anti-calcifying effect of canagliflozin beyond canonical SGLT2 inhibition

Background: Sodium-glucose cotransporter 2 inhibitors (SGLT2i) provide important cardiorenal benefits in chronic kidney disease (CKD), but their effects on vascular calcification remain conflicting. Whether potential anti-calcifying effects are shared across gliflozins or involve mechanisms beyond canonical SGLT2 inhibition is unknown. Methods: We systematically compared canagliflozin, dapagliflozin and empagliflozin in a high-phosphate diet-induced mouse model of vascular calcification and complementary ex vivo and in vitro models, including rodent and human vascular tissues and vascular smooth muscle cells (VSMCs). Aortic transcriptional response was investigated by RNA sequencing. VSMC calcification, proliferation, migration, viability, glucose uptake and bioenergetics were investigated using complementary cellular assays, including OsteoSense staining, Annexin V/propidium iodide staining, radiolabeled 2-deoxyglucose uptake and Seahorse ATP rate analysis. SGLT2/1 expression was examined by RT-qPCR, Western blotting and immunofluorescence. We also evaluated sotagliflozin, a dual SGLT1/2 inhibitor, and mizagliflozin, a selective SGLT1 inhibitor. Results: Among the three gliflozins, only canagliflozin significantly reduced aortic calcification in vivo. Its anti-calcifying effect was also observed in rodent aortic rings, human vascular explants, cultured VSMCs and aortic rings from diabetic db/db mice. Aortic RNA-seq revealed that canagliflozin partially reversed HPD-induced transcriptional alterations, including changes in pro-calcific signaling and cellular metabolism, while some endothelial and inflammatory responses were shared among gliflozins. In mouse VSMCs, canagliflozin reduced calcification across all tested concentrations, dose-dependently decreased osteogenic marker expression, and reduced proliferation and migration. Increased apoptotic and damaged cell fractions were observed at higher concentrations, but not at lower concentrations. Canagliflozin also reduced glucose uptake and mitochondrial ATP production, without significantly affecting glycolytic ATP production. Neither dapagliflozin nor empagliflozin reproduced these cellular and metabolic effects at any of the concentrations tested. SGLT2 and SGLT1 expression was low or undetectable in vascular tissues and cells, and neither sotagliflozin nor mizagliflozin reproduced the anti-calcifying effect of canagliflozin in vivo or in vitro. Conclusions: Canagliflozin exhibits a selective anti-calcifying profile among the gliflozins tested, associated with changes in VSMC responses and cellular metabolism. These findings suggest that its vascular protective effects may involve mechanisms beyond canonical SGLT2 inhibition.

pathology↗

bioRxiv2026

Identification of the Col4a3-/- mouse as a model of chronic kidney disease-associated cachexia

Background: Cachexia is a frequent complication of advanced chronic kidney disease (CKD), i.e. renal cachexia, particularly in patients undergoing hemodialysis in whom it represents one of the strongest predictors of morbidity and mortality. Yet, our understanding of the molecular mechanisms leading to body wasting in CKD and management of cachectic patients are still poorly defined. To date, a preclinical mouse model of robust and reproducible CKD-associated cachexia is missing. Here, we assessed in a systematic manner the cachectic phenotype of the genetic Col4a3-/- mouse model of CKD. Methods: 129/SvJ Col4a3-/- male and female animals were monitored longitudinally until they developed kidney failure. Measured glomerular filtration rate (mGFR), body composition and grip strength were recorded at baseline (6 weeks of age, before onset of kidney dysfunction) and at endpoint (CKD with weight loss or 12 weeks of age). The severity of CKD was confirmed by biochemical and histological analyses. Muscle atrophy was assessed via fiber cross-sectional area analysis, atrogene expression and transcriptomics. Adipose tissue wasting was assessed by measuring adipocyte area and proteins involved in lipid synthesis and breakdown. Liver acute phase response and systemic inflammation were evaluated by measuring circulating levels of key factors using ELISA. Results: Col4a3-/- animals developed CKD (decrease in mGFR: -85%, P<0.0001) and cachexia within 8-12 weeks of age. Cachexia was characterized by a progressive loss of body weight (-17.8% +/- 1.0, P<0.0001), lean (-8.2% +/- 2.0, P<0.0001) and fat mass (-66.5% +/- 4.7, P<0.0001) associated with reduced grip strength (-24.3% +/- 0.0, P=0.0002). At the tissue level, cachexia led to muscle atrophy and induction of atrogenes. Muscle transcriptomics further validated the cachectic phenotype of the Col4a3-/-, with 47% of genes altered in a similar manner with the well-established colon-C26 mouse model of cancer cachexia. It also revealed signatures that appeared more specific to renal cachexia. Adipose tissue wasting was characterized by a depletion in fat stores, consecutive to an imbalance between proteins involved in lipogenesis and lipolysis. Cachexia in this model was also associated with the induction of acute phase response in liver, elevated circulating levels of serum amyloid A and systemic inflammation, with the induction of established cachexia mediators (IL-6, GDF-15 P<0.0001). Both male and female mice developed cachexia. Conclusions: Our data highlight the potential of using the Col4a3-/- mouse model of CKD for the future study of renal cachexia, offering a more robust alternative to classically used models of partial nephrectomy or adenine-rich diet.

pathology↗

bioRxiv2026

Molecular architecture of the ciliary base in mammalian multiciliated cells

Multiciliated epithelial cells (MCCs) generate tens to hundreds of motile cilia to drive fluid flow in diverse physiological contexts. While the axonemal structure of motile cilia has been described extensively in recent years, the molecular architecture of the transition zone, basal body, and surrounding ciliary environment of MCCs remain more elusive. Here, we use cryo-focused ion beam (cryo-FIB) milling and cryo-electron tomography (cryo-ET) to obtain in situ 3D views of the ciliary base within intact MCCs from mammalian trachea, complemented by in situ cross-linking mass spectrometry (XL/MS) and ultrastructure expansion microscopy (U-ExM) for molecular identification. Our data reveal spatially-defined modifications of microtubule architecture from the proximal centriole to the early axoneme, including transition zone-specific features such as an A-B linker bridging microtubule doublets and a helical assembly of microtubule inner proteins (MIPs). We show that the ciliary necklace, a feature observed in many motile cilia, is spatially aligned with the transition zone and quantify its regular organization within the membrane. Our in situ data capture rarely observed events, including intraflagellar transport (IFT) trains connecting to ciliary vesicles tethered to undocked centrioles. The surrounding ciliary environment contains intermediate filaments that encircle the basal bodies and bundled actin filaments that elaborate microvilli structures between the cilia. Integration of XL/MS and U-ExM identified novel microtubule associated proteins (MAPs), MIPs, and membrane-associated proteins localized to these distinct subdomains. This work provides a molecular and structural map of the mammalian MCC ciliary base, revealing architectural principles that underlie its assembly, organization, and function.

cell biology↗

bioRxiv2024

Year-round quantification, structure and dynamics of epibacterial communities from diverse macroalgae reveal a persistent core microbiota and strong host specificities

Macroalgae-bacteria interactions play pivotal ecological roles in coastal ecosystems. Previous characterization of surface microbiota from various macroalgae evidenced fluctuations based on host tissues, physicochemical and environmental parameters. However, the dynamics and degree of similarity of epibacterial communities colonizing phylogenetically distant algae from the same habitat are still elusive. We conducted a year-long monthly epimicrobiota sampling on five algal species inhabiting an English Channel rocky shore: Laminaria digitata, Ascophyllum nodosum, Fucus serratus (brown algae), Palmaria palmata (red alga) and Ulva sp. (green alga). To go beyond relative compositional data and estimate absolute variations in taxa abundance, we combined qPCR measurements of 16S rRNA gene copies with amplicon metabarcoding. A core microbiome composed of 10 genera was consistently found year-round on all algae. Notably, the abundant genus Granulosicoccus stood out for being the only one present in all samples and displayed an important microdiversity. Algal host emerged as the primary driver of epibacterial community composition, before seasonality, and bacterial taxa specifically associated with one or several algae were identified. Moreover, the impact of seasons on the epimicrobiota varied depending on algal tissues. Overall, this study provides an extensive characterization of the microbiota of intertidal macroalgae and enhances our understanding of algal-bacteria holobionts.

microbiology↗

bioRxiv2023

The intrinsically disordered region of the E3 ubiquitin ligase TRIP12 induces the formation of chromatin condensates and interferes with DNA damage response.

Chromatin compaction is crucial for the faithful expression and integrity of the genome. Although largely studied, proteins and mechanisms that control the chromatin compaction are not entirely discovered. We previously showed that the nuclear HECT-type E3 ubiquitin ligase Thyroid hormone Receptor Interacting Protein 12 (TRIP12) is tightly associated to chromatin. As TRIP12 is overexpressed in several types of cancers, we explored herein the consequences of a TRIP12 overexpression on chromatin homeostasis. First, we established the TRIP12 proxisome and unveiled its pleiotropic role in chromatin regulation. Second, we demonstrated that TRIP12 overexpression leads to the formation of chromatin condensates enriched in heterochromatin marks via its intrinsically disordered region (IDR). We further discovered that the formation of TRIP12-mediated chromatin condensates is highly dynamic and driven by a mechanism of phase separation. Chromatin condensate formation depends on the TRIP12 concentration, the length of the TRIP12-IDR and relies on electrostatic interactions. We found that the formation of TRIP12 mediated-condensates alters cell cycle progression, genome accessibility, transcription as well as DNA damage response by inhibiting the accumulation of Mediator of DNA Damage Checkpoint 1 (MDC1). Altogether, this study reveals a novel dynamic role for TRIP12 in chromatin compaction independently of its ubiquitin ligase activity with important consequences on cellular homeostasis. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=155 SRC="FIGDIR/small/556486v1_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@13b3d90org.highwire.dtl.DTLVardef@46b991org.highwire.dtl.DTLVardef@1410bdeorg.highwire.dtl.DTLVardef@1722197_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2023

Alstrom syndrome proteins are novel regulators of centriolar cartwheel assembly and centrosome homeostasis in Drosophila

Centrioles play a central role in cell division by recruiting pericentriolar material (PCM) to form the centrosome. Alterations in centriole number or function lead to various diseases including cancer or microcephaly. Centriole duplication is a highly conserved mechanism in eukaryotes. Here, we show that the two Drosophila orthologs of the Alstrom syndrome protein 1 (Alms1a and Alms1b) are unexpected novel players of centriole duplication in fly. Using Ultrastructure Expansion Microscopy, we reveal that Alms1a is a PCM protein that is loaded proximally on centrioles at the onset of procentriole formation whereas Alms1b caps the base of mature centrioles. We demonstrate that chronic loss of Alms1 proteins affects PCM maturation, whereas their acute loss completely disrupts procentriole formation before Sas-6 cartwheel assembly. We establish that Alms1 proteins are required for the amplification of the Plk4-Ana2 pool at the duplication site and the subsequent Sas-6 recruitment. Thus, Alms1 proteins are novel critical but highly buffered regulators of PCM and cartwheel assembly in flies.

cell biology↗

bioRxiv2023

Seasonal dynamics of a glycan-degrading flavobacterial genus in a tidally-mixed coastal temperate habitat

Coastal marine habitats constitute hotspots of primary productivity. In temperate regions, this is due both to massive phytoplankton blooms and dense colonization by macroalgae that mostly store carbon as glycans, contributing substantially to local and global carbon sequestration. Because they control carbon and energy fluxes, algae-degrading microorganisms are crucial for coastal ecosystem functions. Environmental surveys revealed consistent seasonal dynamics of alga-associated bacterial assemblages, yet resolving what factors regulate the in situ abundance, growth rate and ecological functions of individual taxa remains a challenge. Here, we specifically investigated the seasonal dynamics of abundance and activity for a well-known alga-degrading marine flavobacterial genus in a tidally-mixed coastal habitat of the Western English Channel. We show that members of the genus Zobellia are a stable, low-abundance component of healthy macroalgal microbiota and can also colonize particles in the water column. This genus undergoes recurring seasonal variations with higher abundances in winter, significantly associated to biotic and abiotic variables. Zobellia can become a dominant part of bacterial communities on decaying macroalgae, showing a strong activity and high estimated in situ growth rates. These results provide insights into the seasonal dynamics and environmental constraints driving natural populations of alga-degrading bacteria that influence coastal carbon cycling. Originality-significance statementGlycan-degrading bacteria play a crucial role in marine habitats to remineralize organic carbon sequestered in algal biomass. Yet, resolving what factors regulate the in situ abundance, growth rate and ecological functions of individual taxa remains a challenge. Here, we investigate the seasonal dynamics of abundance and activity of an environmentally relevant glycan-degrading bacterial genus in two constrasted compartments of the same coastal habitat, i.e. the surface of diverse macroalgae and the water column. These results provide insights into the recurring temporal patterns and environmental constraints driving natural populations of alga-degrading bacteria that influence ocean carbon cycling.

microbiology↗

bioRxiv2023

The Loss of the E3 ubiquitin ligase TRIP12 inhibits Pancreatic Acinar Cell Plasticity and Tumor Cell Metastatic Capacity

Background & AimsAlthough specialized and dedicated to the production of digestive enzymes, pancreatic acinar cells harbor a high plasticity and are able to modify their identity. They undergo reversible acinar-to-ductal cell metaplasia (ADM) through epigenetic silencing of the acinar lineage gene program mainly controlled by PTF1a (Pancreas Transcription Factor 1a). ADM becomes irreversible in the presence of oncogenic Kras mutations and leads to the formation of preneoplastic lesions. We investigated the role of the E3 ubiquitin ligase Thyroid hormone Receptor Interacting Protein 12 (TRIP12), involved in PTF1a degradation, in pancreatic carcinogenesis. MethodsWe used genetically engineered mouse models of pancreas-selective Trip12 deletion, mutant Kras (G12D) and mutant Trp53 (R172H). We performed RNA sequencing analysis from acinar cells and cell lines derived from mice models tumors. We investigated the impact of TRIP12 deficiency on acute pancreatitis, tumor formation and metastasis development. ResultsTRIP12 is overexpressed in human pancreatic preneoplastic lesions and tumors. We show that a conditional deletion of TRIP12 in the pancreas during murine embryogenesis alters pancreas homeostasis and acinar cell genes expression patterns in adults. EGF induced-ADM is suppressed in TRIP12-depleted pancreatic acini. In vivo, a loss of TRIP12 prevents acini to develop ADM in response to pancreatic injury, the formation of Kras-induced pancreatic preneoplastic lesions, and impairs tumors and metastasis formation in the presence of mutated Trp53. TRIP12 is required for Claudin18.2 isoform expression in pancreatic tumors cells. ConclusionsOur study identifies TRIP12 as a novel regulator of acinar fate in the adult pancreas with an important dual role in pancreatic carcinogenesis, in initiation steps and in metastatic behavior of tumor cells. SynopsisThis study shows that Thyroid hormone Receptor Interacting Protein 12 plays an important dual role in the initiation steps and invasion of pancreatic carcinogenesis. Moreover, expression of TRIP12 switches on the expression of Claudin-18, a targetable biomarker of pancreatic tumors.

cancer biology↗

bioRxiv2022

MTALTND4, a second protein coded by nd4 impacts mitochondrial bioenergetics

Recent evidence suggests that the coding potential of the mitogenome is underestimated. We found a downstream alternative ATG initiation codon in the +3 reading frame of the human mitochondrial nd4 gene. This newly characterized alternative open reading frame (altORF) encodes a 99-amino acids long polypeptide, MTALTND4, which is conserved in primates. This small protein is localized in mitochondria and cytoplasm and is also found in the plasma, and it impacts mitochondrial physiology. Alternative mitochondrial peptides such as MTALTND4 may offer a new framework for the investigation of mitochondrial functions and diseases.

molecular biology↗

bioRxiv2021

Metabolic strategies of sharing pioneer bacteria mediating fresh macroalgae breakdown

Macroalgae represent huge amounts of biomass worldwide, largely recycled by marine heterotrophic bacteria. We investigated the strategies of "pioneer" bacteria within the flavobacterial genus Zobellia to initiate the degradation of fresh brown macroalgae, which has received little attention compared to the degradation of isolated polysaccharides. Zobellia galactanivorans DsijT could use macroalgae as a sole carbon source and extensively degrade algal tissues without requiring physical contact, via the secretion of extracellular enzymes. This indicated a sharing behaviour, whereby pioneers release public goods that can fuel other bacteria. Comparisons of eight Zobellia strains, and strong transcriptomic shifts in Z. galactanivorans cells using fresh macroalgae vs. isolated polysaccharides, revealed potential overlooked traits of pioneer bacteria. Besides brown algal polysaccharide degradation, they notably include stress resistance proteins, type IX secretion system proteins and novel uncharacterized Polysaccharide Utilization Loci. Overall, this work highlights the relevance of studying fresh macroalga degradation to fully understand the niche, metabolism and evolution of pioneer degraders, as well as their cooperative interactions within microbial communities, as key players in macroalgal biomass turnover.

microbiology↗