Biology subjects

Mathieu, S.

Publications and source records attributed to Mathieu, S..

9 recordsLinked to original sources

bioRxiv2026

Decoding causal genes and programs from regulatory variants in aortic valve disease

Aortic valve disease is common, yet its regulatory mechanisms remain poorly understood. We performed multi-omic profiling of human aortic valve interstitial cells (HAVICs), identifying 11,891 allele-specific chromatin accessibility QTLs (as-caQTLs), 48% novel to this cell type. These variants were enriched in active enhancers, disrupted transcription factor (TF) motifs, particularly AP-1, TEAD and GATA families, and were validated by allele-specific TF binding assays. A fine-tuned deep DNA sequence model prioritized common and rare variants at risk loci predicted to impact chromatin accessibility. Single-cell CRISPRi perturbation of 247 variants identified cis-target genes at 55 as-caQTL elements, including loci without eQTLs. We demonstrate that common regulatory variants controlling elastin and fibrillin impact the development of the aortic valve apparatus. We provide genetic evidence and a mechanistic framework for the contribution of a reduced aortic root size to CAVD risk. Perturbations identified core cell programs led by upstream regulators AHNAK, PDIA6, and RNFT1 converging on extracellular matrix production and iron transport.

genetics↗

bioRxiv2024

De novo RNA base editing in plant organelles with engineered synthetic P-type PPR editing factors

In plant mitochondria and chloroplasts, cytidine-to-uridine RNA editing plays a crucial role in regulating gene expression. While natural PLS-type PPR proteins are specialized in this process, synthetic PPR proteins offer significant potential for targeted RNA editing. In this study, we engineered chimeric editing factors by fusing synthetic P-type PPR guides with the DYW cytidine deaminase domain of a moss mitochondrial editing factor, PPR56. These designer PPR editors (dPPRe) elicited efficient and precise de novo RNA editing in Escherichia coli, and in Nicotiana benthamiana chloroplasts and mitochondria. Chloroplast transcriptome-wide analysis of the most efficient dPPRe revealed minimal off-target effects, with only three non-target C sites edited due to sequence similarity with the intended target. This study introduces a novel and precise method for RNA base editing in plant organelles, paving the way for new approaches in gene regulation applicable to plants and potentially other organisms.

synthetic biology↗

bioRxiv2024

Unbiased and comprehensive identification of viral encoded circular RNAs in a large range of viral species and families

Non-coding RNAs play a significant role in viral infection cycles, with recent attention focused on circular RNAs (circRNAs) originating from various viral families. Notably, these circRNAs have been associated with oncogenesis and alterations in viral fitness. However, identifying their expression has proven more challenging than initially anticipated due to unique viral characteristics. This challenge has the potential to impede progress in our understanding of viral circRNAs. Key hurdles in working with viral genomes include: (1) the presence of repetitive regions that can lead to misalignment of sequencing reads, and (2) unconventional splicing mechanisms that deviate from conserved eukaryotic patterns. To address these challenges, we developed vCircTrappist, a bioinformatic pipeline tailored to identify backsplicing events and pinpoint loci expressing circRNAs in RNA sequencing data. Applying this pipeline, we obtained novel insights from both new and existing datasets encompassing a range of animal and human pathogens belonging to Herpesviridae, Retroviridae, Adenoviridae and Orthomyxoviridae families. Subsequent RT-PCR and Sanger sequencings validated the accuracy of the developed bioinformatic tool for a selection of new candidate viral encoded circRNAs. These findings demonstrate that vCircTrappist is an open and unbiased approach for comprehensive identification of virus-derived circRNAs. Significance StatementCircular RNAs (circRNAs) were revealed to have prominent roles in cellular life in the past decade. They were more recently shown to be expressed by viruses, influencing their infectious cycles and host-pathogen relationship. In this context, viruses that were not previously associated with cellular splicing processes are shown to express circRNAs through unknown mechanisms. These non-canonical circRNAs were already shown to be important in the viral cycle and pathogenesis of the viruses they are encoded from. Here, we propose a bioinformatics pipeline that bypasses the limitations of the existing tools in the identification of viral circRNA. Using this pipeline, we discovered numerous candidates and invite the reader to start its own exploration in the realm of viral encoded circRNAs. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=72 SRC="FIGDIR/small/600382v1_ufig1.gif" ALT="Figure 1"> View larger version (16K): org.highwire.dtl.DTLVardef@1003330org.highwire.dtl.DTLVardef@20d366org.highwire.dtl.DTLVardef@116f38forg.highwire.dtl.DTLVardef@1d04a76_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioinformatics↗

bioRxiv2023

The porphyran degradation system of the human gut microbiota is complete, phylogenetically diverse and geographically structured across Asian populations

The human gut microbiota can acquire new catabolic functions by integrating genetic material coming from the environment, for example from food-associated bacteria. The most illustrative example is the acquisition by the human gut microbiota of Asian populations of genes coming from marine bacteria living on the surface of red algae that are incorporated into their diet when eating maki-sushi. To better understand the function and evolution of this set of algal genes corresponding to a polysaccharide utilization locus (PUL) dedicated to the degradation of porphyran, the main polysaccharide of the red algae Porphyra sp., we characterized it biochemically, assessed its genetic diversity and investigated its geographical distribution in large public worldwide datasets. We first demonstrated that both methylated and unmethylated fractions are catabolized without the help of external enzymes. By scanning the genomic data of more than 10,000 cultivated isolates, we then found that the porphyran PUL organization is conserved in 22 different Bacteroides strains coming from at least 8 species, highlighting multiple lateral transfers within the gut microbiota. We then analyzed the metagenomic data of more than 14,000 individuals coming from 32 countries worldwide and showed that the porphyran PUL exists only in East Asia (Japan, China, Korea), but not anywhere else. Finally, we identified three major PUL haplotypes which frequency differ between countries. This geographic structure is likely the reflect of the rate of bacterial horizontal transmission between individuals. BackgroundThe human gut microbiota can acquire new catabolic functions by integrating genetic material coming from the environment, for example from food-associated bacteria. The most illustrative example is the acquisition by the gut microbiota of Asian populations of genes coming from marine bacteria living on the surface of red algae that are incorporated into their diet when eating maki-sushi. To better understand the function and evolution of this set of algal genes corresponding to a polysaccharide utilization locus (PUL) dedicated to the degradation of porphyran, the main polysaccharide of the red algae Porphyra sp., we characterized it biochemically, assessed its genetic diversity and investigated its geographical distribution in large public worldwide datasets. ResultsWe first demonstrated that both methylated and unmethylated fractions of porphyran are catabolized by the porphyran PUL without the help of external enzymes. By scanning the genomic data of more than 10,000 cultivated isolates, we then found that the porphyran PUL organization is conserved in 22 different Bacteroides strains coming from at least 8 species, highlighting multiple lateral transfers within the gut microbiota. We then analyzed the metagenomic data of more than 14,000 individuals coming from 32 countries worldwide and confirmed that the porphyran PUL exists only in East Asia (Japan, China, Korea). We identified three major porphyran PUL haplotypes which frequency differ between countries. ConclusionThe encoded genes of the PUL porphyran can autonomously catabolized all the complex porphyran structure. The PUL is further encoded by a variety of bacterial species, and its genetic diversity is geographically structured, likely reflecting the rate of bacterial horizontal transmission between individuals.

biochemistry↗

bioRxiv2021

A new approach to measure forces at junction vertices in an epithelium

The mechanical properties of cell-cell junctions are critical for the stability of an epithelium. Cell-cell junction ablation experiments are classically used as a readout for junctional mechanics. However, without the knowledge of the viscoelastic properties of the microenvironment of the ablated junction, tensile junctional forces cannot be measured. Here we combine laser ablation with intracellular microrheology and develop a model to measure tensile forces exerted on cell-cell junctions. We show that the overexpression of the proto-oncogene atypical Protein Kinase C iota (aPKCi) in a single cell within a normal epithelium induces a gradient of junctional tension with neighbouring cells. Our method allows us to demonstrate that junctions contacting the aPKCi-overexpressing cell display a mechanical asymmetry which correlates with the levels of E-cadherin and P-MLC2. Measuring intracellular viscoelasticity is crucial for accurate measurements of cell-cell junction mechanics in the context of development or cancer research. TeaserWe combine cytoplasmic and junctional mechanics to detect asymmetry in forces exerted on cell-cell junctions.

cell biology↗

bioRxiv2020

More filtering on SNP calling does not remove evidence of inter-nucleus recombination in dikaryotic arbuscular mycorrhizal fungi

We respond to a recent reanalysis of single nucleus sequence data from Chen et al. 2018 eLife, which indicated that evidence of inter-nuclear recombination in dikaryotic arbuscular mycorrhizal fungi decreases when heterozygous, duplicated sites being supported by less than 5 reads, are removed from the dataset. Here, we show that applying a more stringent methodology for filtering SNP calls that focuses exclusively on single copy and homozygous regions with at least 5 reads supporting a given SNP, still recovers several hundreds putative inter-nucleus recombination events within the same dataset. We also provide evidence for retaining SNPs supported by less than 5 reads for genotyping individual nuclei using the same dataset.

genomics↗

bioRxiv2019

In-Depth Characterization and Validation in BRG1-Mutant Lung Cancers Define Novel Catalytic Inhibitors of SWI/SNF Chromatin Remodeling

Members of the ATP-dependent SWI/SNF chromatin remodeling complexes are among the most frequently mutated genes in cancer, suggesting their dysregulation plays a critical role. The synthetic lethality between SWI/SNF catalytic subunits BRM/SMARCA2 and BRG1/SMARCA4 has instigated great interest in targeting BRM. Here we have performed a critical and in-depth investigation of novel dual inhibitors (BRM011 and BRM014) of BRM and BRG1 in order to validate their utility as chemical probes of SWI/SNF catalytic function, while obtaining insights into the therapeutic potential of SWI/SNF inhibition. In corroboration of on-target activity, we discovered compound resistant mutations through pooled screening of BRM variants in BRG1-mut cancer cells. Strikingly, genome-wide transcriptional and chromatin profiling (ATAC-Seq) provided further evidence of pharmacological perturbation of SWI/SNF chromatin remodeling as BRM011 treatment induced specific changes in chromatin accessibility and gene expression similar to genetic depletion of BRM. Finally, these compounds have the capacity to inhibit the growth of tumor-xenografts, yielding important insights into the feasibility of developing BRM/BRG1 ATPase inhibitors for the treatment of BRG1-mut lung cancers. Overall, our studies not only establish the feasibility of inhibiting SWI/SNF catalytic function, providing a framework for SWI/SNF therapeutic targeting, but have also yielded successful elucidation of small-molecule inhibitors that will be of importance in probing SWI/SNF function in various disease contexts.

cancer biology↗

bioRxiv2019

Role of a kinesin motor in cancer cell mechanics

Molecular motors play important roles in force generation, migration and intracellular trafficking. Changes in specific motor activities are altered in numerous diseases. KIF20A, a motor protein of the kinesin-6 family, is overexpressed in bladder cancer, and KIF20A levels correlate negatively with the clinical outcome. We report here a new role for the KIF20A kinesin motor protein in intracellular mechanics. Using optical tweezers to probe intracellular mechanics and surface AFM to probe cortical mechanics, we first confirm that bladder cells soften with increasing cancer grade. We then show that inhibiting KIF20A makes the intracellular environment softer for both high and low grade bladder cancer cells. Upon inhibition of KIF20A cortical stiffness also decreases in lower grade cells, while it surprisingly increases in higher grade malignant cells. Changes in cortical stiffness correlate with the interaction of KIF20A with myosin IIA. Moreover, KIF20A negatively regulates bladder cancer cell motility irrespective of the underlying substrate stiffness. Our results reveal a central role for a microtubule motor in cell mechanics and migration in the context of bladder cancer.

biophysics↗

bioRxiv2018

Elucidating the roles of Alzheimer disease-associated proteases and the signal-peptide peptidase-like 3 (SPPL3) in the shedding of glycosyltransferases

The Golgi resident glycosyltransferases (GTs) are membrane-bound glycoproteins but are frequently found as soluble proteins in biological fluids where their function remains largely unknown. Previous studies have established that the release of these proteins involved Alzheimer disease-associated proteases such as {beta}-secretases (BACE1 and BACE2) and the intramembrane-cleaving aspartyl proteases Presenilins 1 and 2. Recent studies have involved another intramembrane-cleaving enzyme, the signal peptide peptidese-like-3 (SPPL3). Except for the latter, the two former studies mostly addressed particular cases of GTs, namely ST6Gal-I (BACEs) or GnT-V (Presenilins). Therefore the question still remains as which of these secretases is truly responsible for the cleavage and secretion of GTs. We herein combined the 3 proteases in a single study with respect to their abilities to release 3 families of GTs encompassing three N-acetylglucosaminyltransferases, two fucosyltransferases and two sialyltransferases. Green fluorescent protein (gfp)-fused versions of these GTs were virally transduced in mouse embryonic fibroblasts devoid of BACEs, Presenilins or SPPL3. We found that neither BACE nor Presenilins are involved in the shedding of these glycosyltransferases, while SPPL3 was involved in the cleavage and release of some but not all GTs. Notably, the {gamma}- secretase inhibitor DFK-167 was the only molecule capable of significantly decreasing glycosyltransferase secretion, suggesting the involvement of {gamma}-secretase(s), yet different from Presenilins but comprising SPPL3 among other proteases still to be identified. Using confocal microscopy, we show that SPPL3 selectivity towards GTs relays not only on sequence specificity but also depends on how GTs distribute in the cell with respect SPPL3 during their cycling within and outside the Golgi.

biochemistry↗