Biology subjects

Raynaud, C.

Publications and source records attributed to Raynaud, C..

12 recordsLinked to original sources

bioRxiv2026

Macrophage renewal in the small intestine governs early-life control of streptococci

Group B Streptococcus (GBS) is both a common intestinal colonizer that is transmitted intergenerationally, and a primary cause of neonatal sepsis worldwide. However, the innate immune mechanisms that restrict the pathogen at the intestinal barrier early in life remain poorly understood. Using an enteral GBS-colonization model in infant mice, we found that lamina-propria (LP) macrophages controlled both GBS-colonization densities and invasion in an age-dependent fashion. LP macrophages turnover and differentiation were strongly impacted by topology. In the small intestine, monocytes infiltration of the LP occurred from birth on in response to perinatally acquired microbiota, whereas in the colon it was driven by the weaning reaction. Moreover, macrophages of the small intestine mounted a robust, MyD88-dependent inflammatory response to GBS, while those of the colon remained largely unaffected. Together, these findings demonstrate that region-specific macrophage dynamics early in life critically influence host-pathogen-interactions during GBS-colonization.

immunology↗

bioRxiv2025

Mitochondrial dysfunction precedes neurodegeneration in DRPLA patient-derived neurons, and phenylbutyrate improves survival.

Dentatorubral-pallidoluysian atrophy (DRPLA) is a progressive autosomal-dominant neurodegenerative disorder caused by a CAG repeat expansion in the ATN1 gene, which encodes the transcriptional corepressor Atrophin-1. The temporal sequence of molecular mechanisms driving neuronal dysfunction and degeneration in DRPLA is poorly understood, limiting therapeutic development. We generated patient-derived induced pluripotent stem cells and differentiated them into cortical excitatory glutamatergic neurons to model early pathogenic processes. Early pathological features of DRPLA patient-derived neurons included mitochondrial dysfunction and oxidative stress. These alterations occurred before overt neuronal loss, highlighting bioenergetic stress as a key early driver of disease progression toward neurodegeneration. Pharmacological treatment with phenylbutyrate significantly improved neuronal survival and reduced mitochondrial reactive oxygen species production, demonstrating the therapeutic potential of targeting mitochondrial dysfunction and oxidative stress. These findings challenge the conventional aggregation-centric model of polyglutamine disease pathogenesis and position mitochondrial stress as a central and early promoter of neuronal degeneration in DRPLA. By providing mechanistic insight into early-stage disease processes, our study lays the foundation for therapeutic strategies targeting mitochondrial dysfunction in DRPLA and related polyglutamine disorders.

neuroscience↗

bioRxiv2023

The CRL plastid outer envelope protein supports TOC75-V / OEP80 complex formation in Arabidopsis

Embedded {beta}-barrel proteins in the outer envelope membrane mediate most cellular traffic between the cytoplasm and the plastids. Although TOC75-V/OEP80 has been implicated in the insertion and assembly of {beta}-barrel proteins in the outer envelope membrane of Arabidopsis thaliana, relatively little is known about this process. CRUMPLED LEAF (CRL) encodes a protein localizing in the outer envelope membrane, and its loss of function results in pleiotropic defects, including altered plant morphogenesis, growth retardation, suppression of plastid division, and spontaneous light intensity-dependent localized cell death. A suppressor screen conducted on mutagenized crl mutants with ethyl methanesulfonate revealed that a missense mutation in OEP80 suppresses crls pleiotropic defects. Furthermore, we found that the complex formation of OEP80 was compromised in crl. Furthermore, we demonstrated that CRL interacts with OEP80 in vivo and that a portion of CRL is present in protein complexes with the same molecular weight as the OEP80-associated complex. Our results suggest that CRL interacts with OEP80 to regulate its complex formation. CRL has been shown to be involved in plastid protein import; therefore, pleiotropic defects in crl are likely due to the combined effects of decreased plastid protein import and altered membrane integration of {beta}-barrel proteins in the outer envelope membrane. This study sheds light on the mechanisms that allow the integration of {beta}-barrel proteins into the outer envelope membrane of plastids and the significance of this finding for plant cellular processes.

plant biology↗

bioRxiv2023

Distinctive and complementary roles of E2F transcription factors during plant replication stress response

Survival of living organisms is fully dependent on their maintenance of genome integrity, being permanently threatened by replication stress in proliferating cells. Although the plant DNA damage response (DDR) regulator SOG1 has been demonstrated to cope with replicative defects, accumulating evidence points to other pathways functioning independently of SOG1. Here, we have studied the role of the Arabidopsis E2FA and EF2B transcription factors, two well-characterized regulators of DNA replication, in the response to replication stress. Through a combination of reverse genetics and chromatin-immunoprecipitation approaches, we show that E2FA and E2FB share many target genes with SOG1, providing evidence for their involvement in the DDR. Analysis of double and triple mutant combinations revealed that E2FB, rather than E2FA, plays the most prominent role in sustaining growth in the presence of replicative defects, either operating antagonistically or synergistically with SOG1. Reversely, SOG1 aids in overcoming the replication defects of E2FA/E2FB-deficient plants. Our data reveal a complex transcriptional network controlling the replication stress response, in which both E2Fs and SOG1 act as key regulatory factors. ONE-SENTENCE SUMMARYThe Arabidopsis E2FA and EF2B transcription factors differently contribute to the plants response to DNA replication defects in a cooperative way with the DNA damage response regulator SOG1.

genetics↗

bioRxiv2022

The canonical E2Fs together with RETINOBLASTOMA-RELATED are required to establish quiescence during plant development

Maintaining stable and transient quiescence in differentiated and stem cells, respectively, requires repression of the cell cycle. The plant RETINOBLASTOMA-RELATED (RBR) has been implicated in stem cell maintenance, presumably by forming repressor complexes with E2F transcription factors. Surprisingly we find that mutations in all three canonical E2Fs do not compromise the cell cycle, but similarly to RBR silencing, result in overproliferation. Contrary to the growth arrest upon RBR silencing, when exit from proliferation to differentiation is inhibited, the e2fabc mutant develops enlarged organs with supernumerary stem and differentiated cells as the quiescence is compromised. While E2F, RBR and the M-phase regulatory MYB3Rs are part of the DREAM repressor complexes, and recruited to overlapping groups of targets, they regulate distinct sets of genes. Only the loss of E2Fs but not the MYB3Rs interferes with quiescence, which might be due to the ability of E2Fs to control both G1-S and some key G2-M targets. We conclude that collectively the three canonical E2Fs in complex with RBR have central roles in establishing cellular quiescence during organ development, leading to enhanced plant growth.

plant biology↗

bioRxiv2022

Full structure/function analysis of all the pilin subunits in a type 4 pilus: a complex of minor pilins in Streptococcus sanguinis mediates binding to glycans

Type 4 filaments (T4F) - of which type 4 pili (T4P) are the archetype - are a superfamily of filamentous nanomachines nearly ubiquitous in prokaryotes. T4F are polymers of one major pilin that also contain minor pilins whose roles are often poorly understood. Here, we complete the structure/function analysis of the full set of T4P pilins in the opportunistic pathogen Streptococcus sanguinis. We determined the structure of the minor pilin PilA, which is unexpectedly similar to one of the subunits of a tip-located complex of four minor pilins, widely conserved in T4F. We found that PilA interacts and dramatically stabilises the minor pilin PilC. We determined the structure of PilC, showing that it is a modular pilin with a lectin module binding a specific subset of glycans prevalent in the human glycome, the host of S. sanguinis. Altogether, our findings support a model whereby the minor pilins in S. sanguinis T4P form a tip-located complex promoting adhesion to various host receptors. Our findings have general implications for a group of minor pilins widely conserved in T4F.

microbiology↗

bioRxiv2021

A hierarchical transcriptional network activates specific CDK inhibitors that regulate G2 to control cell size and number in Arabidopsis

How cell size and number are determined during organ development remains a fundamental question in cell biology. Here, we identified a GRAS family transcription factor, called SCARECROW-LIKE28 (SCL28), with a critical role in determining cell size in Arabidopsis. SCL28 is part of a transcriptional regulatory network downstream of the central MYB3Rs that regulate G2 to M phase cell cycle transition. We show that SCL28 forms a dimer with the AP2-type transcription factor, AtSMOS1, which defines the specificity for promoter binding and directly activates transcription of a specific set of SIAMESE-RELATED (SMR) family genes, encoding plant-specific inhibitors of cyclin-dependent kinases and thus inhibiting cell cycle progression at G2 and promoting the onset of endoreplication. Through this dose-dependent regulation of SMR transcription, SCL28 quantitatively sets the balance between cell size and number without dramatically changing final organ size. We propose that this hierarchical transcriptional network constitutes a cell cycle regulatory mechanism that allows to adjust cell size and number to attain robust organ growth.

plant biology↗

bioRxiv2021

PilB from Streptococcus sanguinis is a bimodular type IV pilin with a direct role in adhesion

Type IV pili (T4P) are functionally versatile filamentous nanomachines, nearly ubiquitous in prokaryotes. They are predominantly polymers of one major pilin, but also contain minor pilins whose functions are often poorly defined, and likely to be diverse. Here, we show that the minor pilin PilB from the T4P of S. sanguinis displays an unusual bimodular 3D structure, with a bulky von Willebrand factor A-like (vWA) module "grafted" onto a small pilin module via a short unstructured loop. Structural modelling suggests that PilB is only compatible with a localisation at the tip of T4P. By performing a detailed functional analysis, we found that (i) the vWA module contains a canonical metal ion-dependent adhesion site (MIDAS), preferentially binding Mg2+ and Mn2+, (ii) abolishing metal-binding has no impact on the structure of PilB or piliation, (iii) metal-binding is important for S. sanguinis T4P-mediated twitching motility and adhesion to eukaryotic cells, and (iv) the vWA module shows an intrinsic binding ability to several host proteins. These findings reveal an elegant, yet simple, evolutionary tinkering strategy to increase T4P functional versatility, by grafting an adhesive module onto a pilin for presentation by the filaments. This strategy appears to have been extensively used by bacteria, in which modular pilins are widespread and exhibit an astonishing variety of architectures.

microbiology↗

bioRxiv2020

A new role for histone demethylases in the maintenance of plant genome integrity

Histone modifications deposited by the Polycomb repressive complex 2 (PRC2) play a critical role in the control of growth, development and adaptation to environmental fluctuations in most multicellular eukaryotes. The catalytic activity of PRC2 is counteracted by Jumonji-type (JMJ) histone demethylases, which shapes the genomic distribution of H3K27me3. Here, we show that two JMJ histone demethylases in Arabidopsis, EARLY FLOWERING 6 (ELF6) and RELATIVE OF EARLY FLOWERING 6 (REF6), play distinct roles in H3K27me3 and H3K27me1 homeostasis. We show that failure to reset these chromatin marks during sexual reproduction results in the inheritance of epigenetic imprints, which cause a loss of DNA methylation at heterochromatic loci and transposon activation. Thus, Jumonji-type histone demethylases in plants contribute towards maintaining distinct transcriptional states during development and help safeguard genome integrity following sexual reproduction.

plant biology↗

bioRxiv2019

RADA is the main branch migration factor in plant mitochondrial recombination and its defect leads to mtDNA instability and cell cycle arrest

The mitochondria of flowering plants have large and complex genomes whose structure and segregation are modulated by recombination activities. The late steps of mitochondrial recombination are still poorly characterized: while the loss of mitochondrial recombination is not viable, a deficiency in RECG1-dependent branch migration has little impact on plant development, implying the existence of alternative pathways. Here we present RADA, an ortholog of bacterial RadA/Sms, which is required for the processing of organellar recombination intermediates. While bacterial RadA is dispensable, RADA-deficient plants are severely impacted in their development and fertility, correlating with increased mtDNA ectopic recombination and replication of recombination-generated subgenomes. The radA mutation is epistatic to recG1, indicating that RADA drives the main branch migration pathway of plant mitochondria. In contrast, the double mutation radA recA3 is lethal, underlining the importance of an alternative RECA3-dependent pathway. Although RADA is dually targeted to mitochondria and chloroplasts, we found little to no effects of radA on the stability of the plastidial genome. The stunted growth of radA mutants could not be correlated with obvious defects in mitochondrial gene expression. Rather, it seems that is partially caused by a retrograde signal that activates nuclear genes repressing cell cycle progression.

plant biology↗

bioRxiv2018

Ancient Yersinia pestis genomes from across Western Europe reveal early diversification during the First Pandemic (541-750)

The first historically documented pandemic caused by Yersinia pestis started as the Justinianic Plague in 541 within the Roman Empire and continued as the so-called First Pandemic until 750. Although palaeogenomic studies have previously identified the causative agent as Y. pestis, little is known about the bacteriums spread, diversity and genetic history over the course of the pandemic.\n\nTo elucidate the microevolution of the bacterium during this time period, we screened human remains from 20 sites in Austria, Britain, Germany, France and Spain for Y. pestis DNA and reconstructed six new genomes. We present a novel methodological approach assessing SNPs in ancient bacterial genomes, facilitating qualitative analyses of low coverage genomes from a metagenomic background. Phylogenetic analysis reveals the existence of previously undocumented Y. pestis diversity during the 6th-7th centuries, and provides evidence for the presence of multiple distinct Y. pestis strains in Europe. We offer genetic evidence for the presence of the Justinianic Plague in the British Isles, previously only hypothesized from ambiguous documentary accounts, as well as southern France and Spain, and that southern Germany seems to have been affected by at least two distinct Y. pestis strains. Four of the reported strains form a polytomy similar to others seen across the Y. pestis phylogeny, associated with the Second and Third Pandemics. We identified a deletion of a 45 kb genomic region in the most recent First Pandemic strain affecting two virulence factors, intriguingly overlapping with a deletion found in 17th-18th-century genomes of the Second Pandemic.\n\nSignificance StatementThe first historically reported pandemic attributed to Yersinia pestis started with the Justinianic Plague (541-544) and continued for around 200 years as the so-called First Pandemic. To date, only one Y. pestis strain from this pandemic has been reconstructed using ancient DNA. In this study, we present six new genomes from Britain, France, Germany and Spain, demonstrating the geographic range of plague during the First pandemic and showing microdiversity in the Early Medieval Period. Moreover, we detect similar genome decay during the First and Second Pandemic (17th to 18th century) that includes the same two virulence factors, thus providing an example of potential convergent evolution of Y. pestis during large scale epidemics.

evolutionary biology↗

bioRxiv2018

In depth biochemical and structural analysis of a Gram-positive type IV pilus

Type IV pili (Tfp) are functionally versatile filaments, widespread in prokaryotes, that belong to a large class of filamentous nanomachines known as type IV filaments (Tff). Although Tfp have been extensively studied in several Gram-negative pathogens where they function as key virulence factors, many aspects of their biology remain poorly understood. Here, we performed a global biochemical and structural analysis of Tfp in a recently emerged Gram-positive model, Streptococcus sanguinis. In particular, we focused on the five pilins and pilin-like proteins involved in Tfp biology in S. sanguinis. We found that the two major pilins, PilE1 and PilE2, (i) follow widely conserved principles for processing by the prepilin peptidase PilD and for assembly into filaments; (ii) display only one of the post-translational modifications frequently found in pilins, i.e. a methylated N-terminus; (iii) are found in the same hetero-polymeric filaments; and (iv) are not functionally equivalent. The 3D structure of PilE1, solved by NMR, revealed a classical pilin fold with a highly unusual flexible C-terminus. Intriguingly, PilE1 more closely resembles pseudopilins forming shorter Tff than bona fide Tfp-forming major pilins, underlining the evolutionary relatedness among different Tff. Finally, we show that S. sanguinis Tfp contain a low abundance of three additional proteins processed by PilD, the minor pilins PilA, PilB, and PilC. These findings provide the first global biochemical and structural picture of a Gram-positive Tfp and have fundamental implications for our understanding of a widespread class of filamentous nanomachines.

microbiology↗