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Fast and accurate quantification of double-strand breaks in microsatellites by digital PCR
No full textInternational audienceDNA double-strand breaks (DSBs) represent critical events in genome integrity, arising from both endogenous cellular processes and exogenous factors. These breaks are implicated in various genomic aberrations and chromosomal rearrangements, leading to cancers and genetic disorders. Common and rare fragile sites, containing repetitive elements and non-B DNA structures, are particularly prone to breakage under replication stress, which play a pivotal role in cancer development and genetic diseases. Accurate quantification of DNA breaks in the context of repetitive sequences such as microsatellites or non-B DNA structures is technically challenging. We have been comparing four different methods to reliably quantify DSBs in repetitive DNA, namely Southern blot, DSB-PCR, real-time DSB-qPCR, and digital PCR (dPCR). We show here that dPCR offers enhanced sensitivity and specificity compared to other methods. This provides significant applications for future disease diagnosis, understanding molecular mechanisms generating chromosomal breakage and for the development of gene therapies for microsatellite expansion disorders
IRF3 in viral infections: more than just triggering the interferon response
No full textInternational audienceInterferon regulatory factor 3 (IRF3) is the first transcription factor activating the expression of type I interferons (IFN-I). It is present in the cytoplasm of most cell types under basal conditions and its activation by phosphorylation allows a rapid triggering of the IFN-I pathway in response to viral infection. This activation of IFN-I is amplified by IRF7, the other major IFN-I transcription factor which expression is induced, in most cell types, by the interferon response. However, recent data have shown that the role of IRF3 in viral infection extends beyond the IFN-I pathway. Here, we review the studies investigating the impact of IRF3 deficiencies in infected cells and in vivo, in mice and in humans. We discuss the discrepancies between and within studies, between isolated cells and whole organisms. While IRF3 is also involved in other pathological processes, we highlight how the newly discovered functions of IRF3 deepen our understanding of its multiple roles in viral infections, which could stimulate the development of pharmacological manipulation of its biological activities
Adjunctive phage therapy improves antibiotic treatment of ventilator-associated-pneumonia with Pseudomonas aeruginosa
No full textInternational audienceBacterial multidrug resistance poses an urgent challenge for the treatment of critically ill patients developing ventilator-associated pneumonia (VAP). Phage therapy, a potential alternative when conventional antibiotics fail, has been unsuccessful in first clinical trials when used alone. Whether combining antibiotics with phages may enhance effectiveness remains to be tested in experimental models. Here, we use a murine model of Pseudomonas-induced VAP to compare the efficacy of adjunctive phage cocktail for antibiotic therapy to either meropenem or phages alone. Combined treatment in murine VAP results in faster clinical improvement and prevents lung epithelial cell damage. Using human primary epithelial cells to dissect these synergistic effects, we find that adjunctive phage therapy reduces the minimum effective concentration of meropenem and prevents resistance development against both treatments. These findings suggest adjunctive phage therapy represents a promising treatment for MDR-induced VAP, enhancing the effectiveness of both antibiotics and phages while reducing adverse effects
Dengue virus susceptibility in Aedes aegypti linked to natural cytochrome P450 promoter variants
No full textInternational audienceThe mosquito Aedes aegypti is the primary vector for dengue virus (DENV), which infects millions of people annually. Variability in DENV susceptibility among wild Ae. aegypti populations is governed by genetic factors, but specific causal variants are unknown. Here, we identify a cytochrome P450-encoding gene (CYP4G15) whose genetic variants drive differences in DENV susceptibility in a natural Ae. aegypti population. CYP4G15 is transiently upregulated in DENV-resistant midguts, while knockdown increases susceptibility, and transgenic overexpression enhances resistance. A naturally occurring 18-base-pair promoter deletion reduces CYP4G15 expression and confers higher DENV susceptibility. The unexpected role of a cytochrome P450 in DENV susceptibility challenges the long-standing focus on canonical immune pathways and opens new avenues for understanding antiviral defense and DENV transmission in mosquitoes
Bat rabies exposures and safety practices among a self-selecting sample of French bat handlers
No full textInternational audienceEuropean bats can be infected by several lyssaviruses, the causative agents of rabies. These viruses can be transmitted from bats to humans and result in a fatal viral encephalitis. Bat handlers are at special risk of lyssavirus exposure because they regularly handle bats for conservation, scientific, and welfare purposes. Methods: An online survey was conducted among a large French network of bat handlers to evaluate the knowledge and perception of bat lyssavirus risk, safety practices, and bat exposures, as well as factors that might increase exposure risk. Results: Eligible responses were received from 130 bat handlers. Most respondents (89.2 %) reported that they had experienced at least one bat bite since they started handling bats. Awareness of the risk of bat-human lyssavirus transmission was high (82.3 % of respondents). The safety practices were implemented by most respondents: 83.1 % were vaccinated against rabies and 80.8 % systematically used gloves to handle bats. However, gaps between recommendations and practice were noted regarding post-vaccination antirabies periodic serological monitoring and recourse to post-exposure prophylaxis administration after bat exposure.Conclusions: This research provides new prospects for improving the training of bat handlers and compliance with safety practices with regard to the risk of exposure to the bat lyssaviruses
DMP of project "Decontamination measures to restore facilities and the environment after a natural or deliberate re-lease of pathogenic microorganisms"
No full textThe aim of the project is work along different case scenarios in order to address concrete procedures and processes of first responders with actual political focus based on threats caused by pathogenic microorganisms. The scenarios include accidental, deliberate or natural release. This focus grants us the possibility to draw on German and French expertise on first responder side and harmonize procedures between the first responders. We will address one of the capability challenges mentioned frequently after exercises and also in EU projects such as FIRE-IN (www.fire-in.eu). First responders are in the spotlight of this project. Main focus will be on the recovery phase including decontamination measures to restore facilities and the environment, an aspect that is important but still a bottle neck in operations. So far, no clear recommendations or standard operational procedures have been developed for such scenarios in Europe. In order to fit that goal, the project addresses two interconnected issues: the improvement of operational processes and the (further) development of technical methods or devices for detection and decontamination. The operational processes themselves will be explored in two directions. On the one hand, based on the two scenarios, their embedding in institutional and legal structures of biological emergency response will be examined in a Franco-German comparison (referring to responsibilities, internal alarm chains, population warning, reporting channels, deployment of the operational organisation etc.). At the other hand the safety culture of the responsible first responders will be investigated. Referring to the technological developments in automated detection, mirocfluidic cartridges based on nucleic acid analysis will allow for rapid, sensitive and specific identification and quantification of the pathogens. This enables the development and evaluation of whole procedures and technical processes focussed on the operational tactical part and the approach in a societal dimension. For the operational tactical level to pave the ground for a larger test scale on a joint French-German exercise, learning about procedures, basic investigations will be performed in small up to large work space. The work will be focused on the relevant procedures for the CBRNE scenarios "technical accident during transportation of pathogens" and "accidental release of pathogens from a production facility". The aim is to identify relevant parameters for the development of operational process data. This will help to elaborate a parameter map for decontamination processes, in order to respond adequately to biological threats. Additionally, procedures for special decontamination requirements, like different materials in sensitive rooms to be recovered, as well as vehicle decontamination (here we use existing equipment) will be developed and evaluated in a test environment. Finally, a scale-up to a large room will be investigated, and procedures will also be developed and evaluated in a test environment in order to develop recommendations to be applied in possible scenarios posing biological threats
Ancestral [Fe-S] biogenesis system SMS has a unique mechanism of cluster assembly and sulfur utilization
No full textInternational audience[Fe-S] clusters are ancient and ubiquitous protein co-factors, which contributed to the emergence of life in an anoxic planet. We have recently identified two minimal [Fe-S] biogenesis systems, MIS and SMS, inferred to be ancestral systems dating back to the Last Universal Common Ancestor and which gave rise to the well-studied modern Iron-Sulfur Cluster (ISC), Nitrogen Fixation (NIF), and Sulfur Mobilization (SUF) machineries. The present study focuses on the ancestor SMS from the hyperthermophilic archaeon Methanocaldococcus jannaschii. Biochemical and structural studies showed that SMS is made of a SmsC2B2 heterotetratmer wherein the SmsC subunit hosts both ATP and [Fe-S] cluster binding sites. Binding of ATP and assembly of [Fe-S] were found to be mutually exclusive allowing for a regulatory coupling between binding of both substrates. Mutagenesis and in vitro transfer experiments revealed the key role of SmsC-contained Cys residues in cluster assembly. Strikingly, the SMS system rescued a non-viable Escherichia coli strain lacking endogenous ISC and SUF systems grown under anoxic conditions, in the presence of Na2S, indicating that sulfide is a source of sulfur for SMS. In addition, we predict that most archaea SmsC proteins hold a similar C-terminal [Fe-S] cluster assembly site. Taking into account those unique structural and functional features, we propose a mechanistic model describing how SmsC2B2 assembles and distributes [4Fe-4S] clusters. Altogether this study established SMS as a new bona fide [Fe-S] biogenesis system that operated in anaerobic prokaryotes prior to evolve to SUF after the Great Oxydation Event
Introduction of epigenetic variation contribute to resistance against the human parasite Schistosoma mansoni
No full textInternational audienceBackgroundWaddington-type kick-start of adaptive evolution is assumed to be possible based on epigenetic variation alone. We tested this hypothesis in the snail Biomphalaria glabrata, vector of Schistosoma mansoni, the causative agent of the human disease schistosomiasis. Epilines and epigenetic recombinant inbred lines (epiRILs) were used to propagate DNA methylation variants over 3 generations.ResultsThe fecundity and susceptibility to infection by S. mansoni were measured. Average parasite prevalence has a higher variance in epiRILs than in controls and decreased from 84 ± 5% in controls to 68 ± 21% in epiRILs. The increase in fertility in epiRILs was 12%, with an average heritability of 0.55. The introduction of 1% epimutant offspring snail into resident susceptible populations was simulated by a model. If genetic assimilation of the resistance occurred in 0.3% of the introduced epimutants, susceptibility would be replaced by resistance after less than one hundred generations.ConclusionsEnvironmental management can therefore be envisaged by introducing epigenetically modified organisms to prevent parasite infections from spreading to the intermediate host and, ultimately, the human population
Reduced adult neurogenesis in humans results from a tradeoff rather than direct negative selection
No full textInternational audienceThe reduction of adult neurogenesis in the human brain, compared to other vertebrate species, has been proposed to result from an active counter-selection to permit the stability of circuits needed for long-term memorization and higher cognitive abilities. Here, bringing forward behavior studies and evolution-based observations, we discuss the benefits of adult neurogenesis and data suggesting that its loss is unlinked with cognitive levels. Considering cell lineages and functional assays, we further note that human-specific genomic features (such as novel gene variants or regulatory sequences) frequently hit pathways that may lead to the premature exhaustion of embryonic neural progenitors after the developmental phase of cortex formation. We propose that reduced adult neurogenesis in humans may be a tradeoff of these changes, themselves selected for to permit the enlargement and complexification of the cerebral cortex during development
Pierre Tiollais (1934-2024), un pionnier du génie génétique et une vie consacrée au virus de l’hépatite B
No full textInternational audiencePierre Tiollais, a French physician-biologist, died on August 5, 2024, at 89. He is celebrated for cloning and sequencing the hepatitis B virus (HBV) genome and developing one of the first recombinant HBV vaccines. Professor at the Pasteur Institute and the University Paris VII (now University Paris Cité), Pierre Tiollais has played a key role in the application of molecular biology and genetic engineering in medical research, notably in the fight against HBV and human immunodeficiency virus (HIV). His work has helped saving millions of lives through vaccination campaigns. Pierre Tiollais was also renowned for his benevolent mentorship and commitment to the scientific community.Pierre Tiollais, médecin et biologiste français, est décédé le 5 août 2024 à l’âge de 89 ans. Il a marqué l’histoire de la médecine par sa contribution au clonage et au séquençage du génome du virus del’hépatite B (VHB), ainsi que par le développement d’un des premiers vaccins recombinants contre ce virus. Professeur à l’Institut Pasteur et à l’Université Paris VII (maintenant Université Paris Cité), il a joué un rôle clé dans l’utilisation de la biologie moléculaire et du génie génétique, notamment dans la lutte contre le VHB et le virus de l’immunodéficience humaine (VIH). Son travail a contribué à sauver des millions de vies humaines grâce à des campagnes de vaccination. Pierre Tiollais était aussi reconnu pour son mentorat bienveillant et son engagement au service de la communauté scientifique