Publications by authors named "Pierre Lechat"

Article Synopsis
  • Defenses against oxidants, particularly superoxide scavenging enzymes (SOSEs), are vital for the survival of pathogens, especially aerobes, but much of the existing knowledge is based on bacteria that have these enzymes.
  • This study explores the evolution of a pathogen lacking SOSEs and how it develops alternative mechanisms to handle superoxide stress, showing that despite losing superoxide dismutase (SOD), it can still adapt effectively.
  • The research highlights the significance of pathways related to cysteine and leucine biosynthesis in combating superoxide and suggests that cysteine oxidation plays a central role in handling superoxide toxicity, challenging traditional views on how bacteria adapt to oxygen-related stress.
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Since the first genome-wide association studies (GWASs), thousands of variant-trait associations have been discovered. However, comprehensively mapping the genetic determinant of complex traits through univariate testing can require prohibitive sample sizes. Multi-trait GWAS can circumvent this issue and improve statistical power by leveraging the joint genetic architecture of human phenotypes.

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Background: As a single reference genome cannot possibly represent all the variation present across human individuals, pangenome graphs have been introduced to incorporate population diversity within a wide range of genomic analyses. Several data structures have been proposed for representing collections of genomes as pangenomes, in particular graphs.

Results: In this work, we collect all publicly available high-quality human haplotypes and construct the largest human pangenome graphs to date, incorporating 52 individuals in addition to two synthetic references (CHM13 and GRCh38).

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Since the first Genome-Wide Association Studies (GWAS), thousands of variant-trait associations have been discovered. However, the sample size required to detect additional variants using standard univariate association screening is increasingly prohibitive. Multi-trait GWAS offers a relevant alternative: it can improve statistical power and lead to new insights about gene function and the joint genetic architecture of human phenotypes.

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Background: Climate change and globalization contribute to the expansion of mosquito vectors and their associated pathogens. Long spared, temperate regions have had to deal with the emergence of arboviruses traditionally confined to tropical regions. Chikungunya virus (CHIKV) was reported for the first time in Europe in 2007, causing a localized outbreak in Italy, which then recurred repeatedly over the years in other European localities.

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The genus includes a large variety of nonpathogenic and life-threatening pathogenic bacteria, which cause a broad spectrum of diseases in humans and animals, such as plague, enteritis, Far East scarlet-like fever (FESLF), and enteric redmouth disease. Like most clinically relevant microorganisms, spp. are currently subjected to intense multi-omics investigations whose numbers have increased extensively in recent years, generating massive amounts of data useful for diagnostic and therapeutic developments.

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Article Synopsis
  • - Pathogenic Leptospira bacteria cause leptospirosis, a severe and widespread zoonotic disease, particularly affecting impoverished populations in sub-tropical regions.
  • - Researchers identified a new PerR-like regulator called PerRB in L. interrogans, which, alongside another regulator PerRA, helps the bacteria adapt to oxidative stress during infection.
  • - The study found that while single mutations in perRA or perRB increased tolerance to specific oxidants, a double mutation rendered the bacteria avirulent, highlighting the complex regulation of virulence through oxidative stress adaptation in pathogenic Leptospira.
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Article Synopsis
  • Genome-wide association studies (GWAS) have identified connections between common genetic variants and various human traits across 36 different phenotypes.
  • This study combines multitrait association mapping with an analysis of genetic variant clusters to understand their genetic architecture and biological implications.
  • The research specifically highlights how these genetic variants relate to immune responses and metabolism, examining their roles in biological pathways and the effectiveness of drug targets in clinical trials.
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Background: Comparing the composition of microbial communities among groups of interest (e.g., patients vs healthy individuals) is a central aspect in microbiome research.

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Article Synopsis
  • GWAS helps connect genetic variants with human traits and diseases, with many summary statistics now publicly available for analysis.
  • The JASS (Joint Analysis of Summary Statistics) Python package provides tools for analyzing multiple phenotypes together to identify new genetic associations, overcoming common challenges in the field.
  • JASS offers features like data cleaning, fast algorithms for joint statistics, and a user-friendly web interface, proving effective in real data applications and available for free online.
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Protozoan parasites of the genus adapt to environmental change through chromosome and gene copy number variations. Only little is known about external or intrinsic factors that govern genomic adaptation. Here, by conducting longitudinal genome analyses of 10 new clinical isolates, we uncovered important differences in gene copy number among genetically highly related strains and revealed gain and loss of gene copies as potential drivers of long-term environmental adaptation in the field.

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Leptospira is a phylogenetically unique group of bacteria, and includes the causative agents of leptospirosis, the most globally prevalent zoonosis. Bacteriophages in Leptospira are largely unexplored. To date, a genomic sequence is available for only one temperate leptophage called LE1.

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Leptospirosis is a widespread zoonosis, potentially severe in humans, caused by spirochetal bacteria, Leptospira interrogans (L. interrogans). Host defense mechanisms involved in leptospirosis are poorly understood.

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As for many model organisms, the amount of omics data produced has recently increased exponentially. There are now >80 published complete genomes, around 350 different transcriptomic data sets, and 25 proteomic data sets available. The analysis of these data sets through a systems biology approach and the generation of tools for biologists to browse these various data are a challenge for bioinformaticians.

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Legionella pneumophila is an environmental bacterium and the leading cause of Legionnaires' disease. Just five sequence types (ST), from more than 2000 currently described, cause nearly half of disease cases in northwest Europe. Here, we report the sequence and analyses of 364 L.

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The biological impact of alternative splicing is poorly understood in fungi, although recent studies have shown that these microorganisms are usually intron-rich. In this study, we re-annotated the genome of C. neoformans var.

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All eukaryotic genomes encode multiple members of the heat shock protein 70 (HSP70) family, which evolved distinctive structural and functional features in response to specific environmental constraints. Phylogenetic analysis of this protein family thus can inform on genetic and molecular mechanisms that drive species-specific environmental adaptation. Here we use the eukaryotic pathogen Leishmania spp.

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The rare patients who are able to spontaneously control HIV replication in the absence of therapy show signs of a particularly efficient cellular immune response. To identify the molecular determinants that underlie this response, we characterized the T cell receptor (TCR) repertoire directed at Gag293, the most immunoprevalent CD4 epitope in the HIV-1 capsid. HIV controllers from the ANRS CODEX cohort showed a highly skewed TCR repertoire that was characterized by a predominance of TRAV24 and TRBV2 variable genes, shared CDR3 motifs, and a high frequency of public clonotypes.

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Streptococcus agalactiae (Group B Streptococcus, GBS) is a commensal of the digestive and genitourinary tracts of humans that emerged as the leading cause of bacterial neonatal infections in Europe and North America during the 1960s. Due to the lack of epidemiological and genomic data, the reasons for this emergence are unknown. Here we show by comparative genome analysis and phylogenetic reconstruction of 229 isolates that the rise of human GBS infections corresponds to the selection and worldwide dissemination of only a few clones.

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For nearly 3 decades, listeriologists and immunologists have used mainly three strains of the same serovar (1/2a) to analyze the virulence of the bacterial pathogen Listeria monocytogenes. The genomes of two of these strains, EGD-e and 10403S, were released in 2001 and 2008, respectively. Here we report the genome sequence of the third reference strain, EGD, and extensive genomic and phenotypic comparisons of the three strains.

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Unlabelled: The intestinal tract is the largest reservoir of microbes in the human body. The intestinal microbiota is thought to be able to modulate alterations of the gut induced by enteropathogens, thereby maintaining homeostasis. Listeria monocytogenes is the agent of listeriosis, an infection transmitted to humans upon ingestion of contaminated food.

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Background: Dynamic visualisation interfaces are required to explore the multiple microbial genome data now available, especially those obtained by high-throughput sequencing - a.k.a.

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Listeria monocytogenes is a foodborne pathogen that crosses the intestinal barrier and disseminates within the host. Here, we report a unique comprehensive analysis of the impact of two Lactobacillus species, Lactobacillus paracasei CNCM I-3689 and Lactobacillus casei BL23, on L. monocytogenes and orally acquired listeriosis in a gnotobiotic humanized mouse model.

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CandidaDB (http://genodb.pasteur.fr/CandidaDB) was established in 2002 to provide the first genomic database for the human fungal pathogen Candida albicans.

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