Biology subjects

Villeneuve, L.

Publications and source records attributed to Villeneuve, L..

4 recordsLinked to original sources

bioRxiv2026

Isw2-mediated chromatin remodeling governs antifungal tolerance and heteroresistance in Candida albicans

Antifungal tolerance, unlike resistance, allows cells to grow slowly at concentrations above the minimum inhibitory concentration. While resistance mechanisms are well characterized, the pathways underlying tolerance remain elusive. Here, we performed a genetic screen of a transcriptional factor mutant library to identify regulators of azole tolerance in Candida albicans. This screen uncovered Isw2, the catalytic subunit of the ISW2 ATP-dependent chromatin remodeling complex, as a negative regulator of azole tolerance. Integrating transcriptomics, Isw2 DNA-binding profiles, and nucleosome-occupancy analyses revealed that Isw2 maintains a repressive chromatin architecture at the CRZ1 promoter, limiting the nucleosome-depleted region and suppressing CRZ1 transcription. Isw2 also modulates fluconazole heteroresistance and amphotericin B sensitivity through Crz1. In addition, we identified the copper-responsive transcription factor Mac1 as a context-dependent regulator of azole tolerance, acting negatively under copper limitation but positively under copper-replete conditions. Together, these findings reveal unexpected roles for chromatin remodeling and copper homeostasis in antifungal tolerance.

microbiology↗

bioRxiv2025

Manganese homeostasis modulates glucan and chitin unmasking in the opportunistic yeast Candida albicans

Candida albicans is a commensal fungus and also the most prevalent human fungal pathogen. The ability of this opportunistic yeast to acquire and maintain homeostatic levels of manganese (Mn), particularly in the metal-limited host environment, is an important determinant of its fitness. Recent studies have underscored the importance of Mn acquisition through members of Smf transporters, in C. albicans virulence and its ability to withstand various stresses. In the present study, we undertook transcriptional profiling in the mutant of the Mn transporter Smf12 under restricted Mn availability to identify processes that are directly affected in defective Mn uptake. Our analysis revealed that smf12 displayed a transcriptional pattern suggestive of a cell wall defect, with many transcripts associated with cell wall biogenesis being differentially regulated. smf12 together with smf11, a mutant of the closest homolog of Smf12, exhibited hypersensitivity to cell wall stressors and an altered cell wall ultrastructure. The smf mutants also exhibited unmasking of both {beta}-glucan and chitin, which unexpectedly resulted in a decreased rate of phagocytosis by macrophages, suggesting impaired recognition or internalization--an observation that challenges the prevailing paradigm. Furthermore, we showed that Mn-mediated unmasking of {beta}-glucan required modulation of glucanase activity and was not mediated through the calcineurin pathway. This study uncovers a novel role for Mn in maintaining cell wall integrity and modulating the exposure of fungal antigenic determinants, further emphasizing the critical role of this metal in supporting the opportunistic nature of C. albicans.

microbiology↗

bioRxiv2025

Inflammatory bowel disease risk gene C1ORF106 regulates actin dynamics in intestinal epithelial cells

Background and aimsC1ORF106 has previously been associated with inflammatory bowel diseases (IBD) via large-scale genetic studies. Increased intestinal permeability is a hallmark of IBD and is observed in at-risk individuals prior to the appearance of clinical symptoms. C1ORF106 was previously shown to regulate intestinal barrier permeability through the regulation of adherens junction stability and through the formation of tight junctions, which impacted actin assembly. However, the downstream impact and molecular mechanisms involved in actin regulation by C1ORF106 havent been explored. Our study aimed at identifying which pathways involved in intestinal epithelial barrier regulation and F-actin regulation are impacted by C1ORF106 and its IBD-associated variant. MethodsWe knocked down (KD) the expression of C1ORF106 in human colonic epithelial cells and characterized the function of the 333F variant in intestinal epithelial spheroid cultures obtained from patient-derived human induced pluripotent stem cell (hiPSC). We measured barrier permeability and characterized spheroid formation, actin regulation and cell migration though immunofluorescence, western blots and permeability assays. ResultsC1ORF106 KD leads to impaired cortical actin belt dynamics and regulation of stress fiber formation, resulting in increased cell constriction, impaired barrier permeability, cell polarity and cell migration. Moreover, we demonstrated that an inhibition of ROCK rescues the actin belt and cell polarity phenotypes in C1ORF106 KD cells, demonstrating that C1ORF106 regulates these phenotypes through a ROCK-dependent mechanism. We also observed an altered nmMYO2-P localization in C1ORF106 KD cells associated with the formation of Vacuolar Apical Compartments (VACs), which are important for 3D epithelial spheroid formation. We observed a similar impact on cell polarity in intestinal epithelial spheroids obtained from hiPSC carrying the 333F variant, providing additional support that this pathway is involved in disease development. ConclusionWe provide insights into the molecular mechanisms by which C1ORF106 controls actin dynamics to regulate intestinal epithelial integrity. summaryC1ORF106 and its inflammatory bowel disease-associated genetic variant regulate intestinal barrier permeability through the regulation of tight junction formation and cell polarity in epithelial cells. This regulation is associated with altered F-actin dynamics that are ROCK-dependent.

genetics↗

bioRxiv2025

Time-dependent Mitochondrial Remodeling in Experimental Atrial Fibrillation and Potential Therapeutic Relevance

BACKGROUNDChanges in mitochondria have been implicated in atrial fibrillation (AF), but their manifestations and significance are poorly understood. Here, we studied changes in mitochondrial morphology and function during AF and assessed the effect of a mitochondrial-targeted intervention in a large animal model. METHODS AND RESULTSAtrial cardiomyocytes (ACMs) were isolated from dogs in electrically-driven AF for periods of 24 hours to 3 weeks and from humans with/without longstanding persistent AF. Mitochondrial Ca2+-concentration ([Ca2+]Mito), reactive oxygen species (mtROS) production, membrane potential ({Delta}{Psi}m), permeability transition-pore (mPTP) opening and flavin adenine dinucleotide (FAD) were measured via confocal microscopy; nicotine adenine dinucleotide (NADH) under ultraviolet light. mtROS-production increased within 24 hours and superoxide-dismutase type-2 was significantly reduced from 3-day AF. [Ca2+]Mito and mPTP-opening frequency/duration increased progressively during AF. Mitochondrial depolarization was detectable 24 hours after AF-onset. NADH increased by 15% at 24-hour AF, concomitant with increased pyruvate-dehydrogenase expression, then gradually decreased. Mitochondria enlarged and elongated at 24-hour and 3-day AF, followed by progressive fragmentation, rupture and shrinkage. Mitochondrial fusion protein-1 (MFN1) was reduced from 3-day to 3-week AF and phosphorylated dynamin-related protein-1 (p-DRP1ser-616) increased after 1 week of canine AF and in human AF. Addition of the mitochondrial antioxidant MitoTempo attenuated action-potential shortening and L-type Ca2+-current (ICaL)-downregulation in canine and human AF ACMs in vitro. Administration of the orally-active mitochondrial-targeted ubiquinone mitoquinone to dogs during 3-week AF prevented mitochondrial Ca2+-overload, mtROS-overproduction, structural damage and abnormalities in {Delta}{Psi}m and respiration. Functionally, mitoquinone reduced AF-induced Ca2+-current downregulation, action-potential abbreviation, contractile dysfunction and fibrosis, preventing AF-substrate development and AF-sustainability. CONCLUSIONSMitochondria show a series of changes during AF, with early hyperfunction and enhanced ROS-generation, followed by progressive damage and dysfunction. Mitochondrial-targeted therapy prevents mitochondrial dysfunction and attenuates adverse AF-related remodeling, positioning mitochondrial protection as a potential novel therapeutic target in AF.

pathology↗