Critical role of the neutrophil-associated high-affinity receptor for IgE in the pathogenesis of experimental cerebral malaria

FcεR1-expressing neutrophils accumulate in the brain of mice infected with Plasmodium berghei (PbANKA) and promote the development of experimental cerebral malaria

Plasmodium-encoded murine IL-6 impairs liver stage infection and elicits long-lasting sterilizing immunity

IntroductionPlasmodium sporozoites (SPZ) inoculated by Anopheles mosquitoes into the skin of the mammalian host migrate to the liver before infecting hepatocytes. Previous work demonstrated that early production of IL-6 in the liver is detrimental for the parasite growth, contributing to the acquisition of a long-lasting immune protection after immunization with live attenuated parasites.MethodsConsidering that IL-6 as a critical pro-inflammatory signal, we explored a novel approach whereby the parasite itself encodes for the murine IL-6 gene. We generated transgenic P. berghei parasites that express murine IL-6 during liver stage development.Results and DiscussionThough IL-6 transgenic SPZ developed into exo-erythrocytic forms in hepatocytes in vitro and in vivo, these parasites were not capable of inducing a blood stage infection in mice. Furthermore, immunization of mice with transgenic IL-6-expressing P. berghei SPZ elicited a long-lasting CD8+ T cell-mediated protective immunity against a subsequent infectious SPZ challenge. Collectively, this study demonstrates that parasite-encoded IL-6 attenuates parasite virulence with abortive liver stage of Plasmodium infection, forming the basis of a novel suicide vaccine strategy to elicit protective antimalarial immunity

Ageing affects DNA methylation drift and transcriptional cell-to-cell variability in mouse muscle stem cells.

Age-related tissue alterations have been associated with a decline in stem cell number and function. Although increased cell-to-cell variability in transcription or epigenetic marks has been proposed to be a major hallmark of ageing, little is known about the molecular diversity of stem cells during ageing. Here we present a single cell multi-omics study of mouse muscle stem cells, combining single-cell transcriptome and DNA methylome profiling. Aged cells show a global increase of uncoordinated transcriptional heterogeneity biased towards genes regulating cell-niche interactions. We find context-dependent alterations of DNA methylation in aged stem cells. Importantly, promoters with increased methylation heterogeneity are associated with increased transcriptional heterogeneity of the genes they drive. These results indicate that epigenetic drift, by accumulation of stochastic DNA methylation changes in promoters, is associated with the degradation of coherent transcriptional networks during stem cell ageing. Furthermore, our observations also shed light on the mechanisms underlying the DNA methylation clock.Includes ERC and BBSR

Myo10 is a key regulator of TNT formation in neuronal cells.

Cell-to-cell communication is essential in multicellular organisms. Tunneling nanotubes (TNTs) have emerged as a new type of intercellular spreading mechanism allowing the transport of various signals, organelles and pathogens. Here, we study the role of the unconventional molecular motor myosin-X (Myo10) in the formation of functional TNTs within neuronal CAD cells. Myo10 protein expression increases the number of TNTs and the transfer of vesicles between co-cultured cells. We also show that TNT formation requires both the motor and tail domains of the protein, and identify the F2 lobe of the FERM domain within the Myo10 tail as necessary for TNT formation. Taken together, these results indicate that, in neuronal cells, TNTs can arise from a subset of Myo10-driven dorsal filopodia, independent of its binding to integrins and N-cadherins. In addition our data highlight the existence of different mechanisms for the establishment and regulation of TNTs in neuronal cells and other cell types

Enquete sur le reseau de drainage: l'exemple du secteur de reference de la Bresse

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USP18 and ISG15 coordinately impact on SKP2 and cell cycle progression

Abstract USP18 is an isopeptidase that cleaves the ubiquitin-like ISG15 from conjugates and is also an essential negative feedback regulator of type I interferon signaling. We and others reported that USP18 protein is stabilized by ISG15 and targeted for degradation by SKP2 (S-phase kinase associated protein 2), the substrate-recognition subunit of the SCFSKP2 ubiquitin E3 ligase complex, which operates in cell cycle progression. Here, we have analyzed how, under non stimulated conditions, USP18, ISG15 and SKP2 communicate with each other, by enforcing or silencing their expression. We found that USP18 and SKP2 interact and that free ISG15 abrogates the complex, liberating USP18 from degradation and concomitantly driving SKP2 to degradation and/or ISGylation. These data reveal a dynamic interplay where the substrate USP18 stabilizes SKP2, both exogenous and endogenous. Consistent with this we show that silencing of baseline USP18 slows down progression of HeLa S3 cells towards S phase. Our findings point to USP18 and ISG15 as unexpected new SKP2 regulators, which aid in cell cycle progression at homeostasis

The cytosolic bacterial peptidoglycan sensor Nod2 affords stem cell protection and links microbes to gut epithelial regeneration

Comment in : Nod-like receptors have a grip on stem cells. [Cell Host Microbe. 2014]International audienceThe intestinal crypt is a site of potential interactions between microbiota products, stem cells, and other cell types found in this niche, including Paneth cells, and thus offers a potential for commensal microbes to influence the host epithelium. However, the complexity of this microenvironment has been a challenge to deciphering the underlying mechanisms. We used in vitro cultured organoids of intestinal crypts from mice, reinforced with in vivo experiments, to examine the crypt-microbiota interface. We find that within the intestinal crypt, Lgr5(+) stem cells constitutively express the cytosolic innate immune sensor Nod2 at levels much higher than in Paneth cells. Nod2 stimulation by its bona fide agonist, muramyl-dipeptide (MDP), a peptidoglycan motif common to all bacteria, triggers stem cell survival, which leads to a strong cytoprotection against oxidative stress-mediated cell death. Thus, gut epithelial restitution is Nod2 dependent and triggered by the presence of microbiota-derived molecules

Identification of recessive lethal alleles in the diploid genome of a candida albicans laboratory strain unveils a potential role of repetitive sequences in buffering their deleterious impact.

International audienceThe heterozygous diploid genome of Candida albicans is highly plastic, with frequent loss of heterozygosity (LOH) events. In the SC5314 laboratory strain, while LOH events are ubiquitous, a chromosome homozygosis bias is observed for certain chromosomes, whereby only one of the two homologs can occur in the homozygous state. This suggests the occurrence of recessive lethal allele(s) (RLA) preventing large-scale LOH events on these chromosomes from being stably maintained. To verify the presence of an RLA on chromosome 7 (Chr7), we utilized a system that allows (i) DNA double-strand break (DSB) induction on Chr7 by the I-SceI endonuclease and (ii) detection of the resulting long-range homozygosis. I-SceI successfully induced a DNA DSB on both Chr7 homologs, generally repaired by gene conversion. Notably, cells homozygous for the right arm of Chr7B were not recovered, confirming the presence of RLA(s) in this region. Genome data mining for RLA candidates identified a premature nonsense-generating single nucleotide polymorphism (SNP) within the HapB allele of C7_03400c whose Saccharomyces cerevisiae ortholog encodes the essential Mtr4 RNA helicase. Complementation with a wild-type copy of MTR4 rescued cells homozygous for the right arm of Chr7B, demonstrating that the mtr4K880* RLA is responsible for the Chr7 homozygosis bias in strain SC5314. Furthermore, we observed that the major repeat sequences (MRS) on Chr7 acted as hot spots for interhomolog recombination. Such recombination events provide C. albicans with increased opportunities to survive DNA DSBs whose repair can lead to homozygosis of recessive lethal or deleterious alleles. This might explain the maintenance of MRS in this species.IMPORTANCE Candida albicans is a major fungal pathogen, whose mode of reproduction is mainly clonal. Its genome is highly tolerant to rearrangements, in particular loss of heterozygosity events, known to unmask recessive lethal and deleterious alleles in heterozygous diploid organisms such as C. albicans By combining a site-specific DSB-inducing system and mining genome sequencing data of 182 C. albicans isolates, we were able to ascribe the chromosome 7 homozygosis bias of the C. albicans laboratory strain SC5314 to an heterozygous SNP introducing a premature STOP codon in the MTR4 gene. We have also proposed genome-wide candidates for new recessive lethal alleles. We additionally observed that the major repeat sequences (MRS) on chromosome 7 acted as hot spots for interhomolog recombination. Maintaining MRS in C. albicans could favor haplotype exchange, of vital importance to LOH events, leading to homozygosis of recessive lethal or deleterious alleles that inevitably accumulate upon clonality