Meisosomes, folded membrane microdomains between the apical extracellular matrix and epidermis

Apical extracellular matrices (aECMs) form a physical barrier to the environment. In Caenorhabditis elegans, the epidermal aECM, the cuticle, is composed mainly of different types of collagen, associated in circumferential ridges separated by furrows. Here, we show that in mutants lacking furrows, the normal intimate connection between the epidermis and the cuticle is lost, specifically at the lateral epidermis, where, in contrast to the dorsal and ventral epidermis, there are no hemidesmosomes. At the ultrastructural level, there is a profound alteration of structures that we term 'meisosomes,' in reference to eisosomes in yeast. We show that meisosomes are composed of stacked parallel folds of the epidermal plasma membrane, alternately filled with cuticle. We propose that just as hemidesmosomes connect the dorsal and ventral epidermis, above the muscles, to the cuticle, meisosomes connect the lateral epidermis to it. Moreover, furrow mutants present marked modifications of the biomechanical properties of their skin and exhibit a constitutive damage response in the epidermis. As meisosomes co-localise to macrodomains enriched in phosphatidylinositol (4,5) bisphosphate, they could conceivably act, like eisosomes, as signalling platforms, to relay tensile information from the aECM to the underlying epidermis, as part of an integrated stress response to damage

Mutant TDP-43 and FUS Cause Age-Dependent Paralysis and Neurodegeneration in C. elegans

Mutations in the DNA/RNA binding proteins TDP-43 and FUS are associated with Amyotrophic Lateral Sclerosis and Frontotemporal Lobar Degeneration. Intracellular accumulations of wild type TDP-43 and FUS are observed in a growing number of late-onset diseases suggesting that TDP-43 and FUS proteinopathies may contribute to multiple neurodegenerative diseases. To better understand the mechanisms of TDP-43 and FUS toxicity we have created transgenic Caenorhabditis elegans strains that express full-length, untagged human TDP-43 and FUS in the worm's GABAergic motor neurons. Transgenic worms expressing mutant TDP-43 and FUS display adult-onset, age-dependent loss of motility, progressive paralysis and neuronal degeneration that is distinct from wild type alleles. Additionally, mutant TDP-43 and FUS proteins are highly insoluble while wild type proteins remain soluble suggesting that protein misfolding may contribute to toxicity. Populations of mutant TDP-43 and FUS transgenics grown on solid media become paralyzed over 7 to 12 days. We have developed a liquid culture assay where the paralysis phenotype evolves over several hours. We introduce C. elegans transgenics for mutant TDP-43 and FUS motor neuron toxicity that may be used for rapid genetic and pharmacological suppressor screening

Diversité des interferons et de leurs récepteurs chez le Danio rerio

Les IFNs sont un groupe de cytokines définis par leur activité antivirale. Chez les mammifères, ils sont divisés en trois groupes. Ils fixent tous des complexes récepteurs distincts et possèdent une structure génique différente. Les types I (principalement a et b) ont un seul exon, le type II (g) quatre exons et le type III ( ) cinq. Les types I et III constituent un sous-groupe connu sous le nom d'IFNs induits par les virus , car ils sont directement induits par une infection virale, alors que le type II ne l'est pas. La présence d'IFN induits par les virus et d'IFNg (possédant 4 exons) ont été signalé dans toute les études poussées chez les poissons, la plupart, sinon tous, possèdent plusieurs gènes codant pour ces IFNs. La classification des IFNs induits par les virus chez les poissons est très controversée, nous avons pris parti de les nommer IFN (possédant 5 exons). Au cours de cette thèse nous avons identifié un IFN en plus appartenant aux IFN s, nous avons caractérisé les propriétés des IFN s et IFNgs et nous avons identifié leurs complexes récepteurs in vivo. Le génome du danio code pour 4 IFN s et 2 IFNgs, nous avons montré que l'expression et le profil d'induction de ces IFNs sont différents, qu'ils possédaient une activité biologique antivirale et que les IFN s étaient capables de protéger contre l'infection virale. Finalement l'utilisation d'expériences de perte et de gain de fonction, nous ont permis d'identifier les composants transmembranaires des complexes récepteursInterferons are a group of cytokines defined by their antiviral activities. In mammals, IFNs are divided into three groups according to their receptor usage. In addition to using distinct receptor complexes, the three mammalian types of IFN also have distinct genetic structure: type I (mainly a and b ) IFN genes have a single exon, type II (g) IFNs have four exons, while type III ( ) IFNs have five. Type I and type III IFNs together constitute a distinct subgroup known as virus-induced IFNs as they are directly induced by viral infections while type II is not. Virus-induced fish IFNs and IFN g (with 4 exons) have now been reported in all deeply studied fish species; most, if not all, teleost species possess several genes encoding these IFNs. The classification of fish virus-induced IFNs remains controversial, we took advantage of naming IFN (with 5 exons). In this work we identified a fourth IFN, which belongs to IFN s, we characterized the properties of IFN s and IFNgs and we have found their receptor complexes in vivo. The danio genome encodes 4 IFN s and 2 IFNgs, we showed that the expression profile and induction of these IFNs are different, they possess antiviral biological activity and the IFN s were able to protect against the viral infection. Using loss of function and gain of function analysis, we finally identified the transmembrane components of their receptor complexesMONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Antagonistic fungal enterotoxins intersect at multiple levels with host innate immune defences

International audienceAnimals and plants need to defend themselves from pathogen attack. Their defences drive innovation in virulence mechanisms, leading to never-ending cycles of co-evolution in both hosts and pathogens. A full understanding of host immunity therefore requires examination of pathogen virulence strategies. Here, we take advantage of the well-studied innate immune system of Caenorhabditis elegans to dissect the action of two virulence factors from its natural fungal pathogen Drechmeria coniospora . We show that these two enterotoxins have strikingly different effects when expressed individually in the nematode epidermis. One is able to interfere with diverse aspects of host cell biology, altering vesicle trafficking and preventing the key STAT-like transcription factor STA-2 from activating defensive antimicrobial peptide gene expression. The second increases STA-2 levels in the nucleus, modifies the nucleolus, and, potentially as a consequence of a host surveillance mechanism, causes increased defence gene expression. Our results highlight the remarkably complex and potentially antagonistic mechanisms that come into play in the interaction between co-evolved hosts and pathogens

In Vivo Analysis of Ifn-gamma 1 and Ifn-gamma 2 Signaling in Zebrafish

The zebrafish genome contains a large number of genes encoding potential cytokine receptor genes as judged by homology to mammalian receptors. The sequences are too divergent to allow unambiguous assignments of all receptors to specific cytokines, and only a few have been assigned functions by functional studies. Among receptors for class II helical cytokines-i.e., IFNs that include virus-induced Ifns (Ifn-phi) and type II Ifns (Ifn-gamma), together with Il-10 and its related cytokines (Il-20, Il-22, and Il-26)-only the Ifn-phi-specific complexes have been functionally identified, whereas the receptors for the two Ifn-gamma (Ifn-gamma 1 and Ifn-gamma 2) are unknown. In this work, we identify conditions in which Ifn-gamma 1 and Ifn-gamma 2 (also called IFNG or IFN-gamma and IFN-gammarel) are induced in fish larvae and adults. We use morpholino-mediated loss-of-function analysis to screen candidate receptors and identify the components of their receptor complexes. We find that Ifn-gamma 1 and Ifn-gamma 2 bind to different receptor complexes. The receptor complex for Ifn-gamma 2 includes cytokine receptor family B (Crfb)6 together with Crfb13 and Crfb17, whereas the receptor complex for Ifn-gamma 1 does not include Crfb6 or Crfb13 but includes Crfb17. We also show that of the two Jak2 paralogues present in the zebrafish Jak2a but not Jak2b is involved in the intracellular transmission of the Ifn-gamma signal. These results shed new light on the evolution of the Ifn-gamma signaling in fish and tetrapods and contribute toward an integrated view of the innate immune regulation in vertebrates. The Journal of Immunology, 2010, 185: 6774-6782

Mutant TDP-43 and FUS impair synaptic transmission.

<p>(A) Cholinergic neuronal transmission was measured by determining the onset of paralysis induced by the cholinesterase inhibitor aldicarb. <i>unc-47(e307)</i> mutants and mTDP-43 transgenics were hypersensitive to aldicarb-induced paralysis compared to either wtTDP-43 transgenics or N2 worms (P<0.001 for <i>unc-47</i> or mTDP-43 compared to N2 or wtTDP-43 worms). (B) mFUS transgenics and <i>unc-47(e307)</i> mutants were more sensitive to aldicarb induced paralysis compared to either wtFUS transgenics or N2 controls (P<0.001). (C) <i>unc-47</i> mutants grown on regular worm plates showed age-dependent progressive paralysis.</p

TDP-43 and FUS transgenes do not affect lifespan.

<p>Beginning at Day 1 of adulthood we tested the lifespans of wild type non-transgenic N2 worms and transgenics expressing (A) wtTDP-43 and mTDP-43 as well as (B) animals expressing wtFUS and mFUS. Animals expressing TDP-43 or FUS transgenes had lifespans indistinguishable from N2 worms.</p

The Two Groups of Zebrafish Virus-Induced Interferons Signal via Distinct Receptors with Specific and Shared Chains

International audienceBecause the availability of fish genomic data, the number of reported sequences for fish type II helical cytokines is rapidly growing, featuring different IFNs including virus-induced IFNs (IFN_) and IFN-_, and IL-10 with its related cytokines (IL-20, IL-22, and IL-26). Many candidate receptors exist for these cytokines and various authors have postulated which receptor chain would be involved in which functional receptor in fish. To date, only the receptor for zebrafish IFN_1 has been identified functionally. Three genes encoding virus-induced IFN_s have been reported in zebrafish. In addition to these genes clustered on chromosome 3, we have identified a fourth IFN_ gene on chromosome 12. All these genes possess the intron-exon organization of mammalian _ IFNs. In the zebrafish larva, all induce the expression of reporter antiviral genes; protection in a viral challenge assay was observed for IFN_1 and IFN_2. Using a combination of gain- and loss-of-function experiments, we also show that all zebrafish IFN_s do not bind to the same receptor. Two subgroups of fish virus-induced IFNs have been defined based on conserved cysteines, and we find that this subdivision correlates with receptor usage. Both receptor complexes include a common short chain receptor (CRFB5) and a specific long chain receptor (CRFB1 or CRFB2)

Mutant TDP-43 and FUS aggregate in vivo.

<p>(A) Representative image of a fixed <i>unc-47p::GFP;mTDP-43</i> worm stained with a human TDP-43 antibody. The green channel shows GFP labelled motor neurons. Antibody staining (red signal) revealed aggregation of TDP-43 signals in motor neurons. Staining of motor neuron nuclei with DAPI (blue signal) revealed that TDP-43 is both cytoplasmic (single arrowhead) and nuclear (double arrowhead). Scale bar represents 10 µm for all photos. (B) Staining of <i>unc-47p::GFP;mFUS</i> worms with a human FUS antibody (red signal) and DAPI (blue signal) revealed cytoplasmic (single arrowhead) and nuclear (double arrowhead) accumulations in motor neurons.</p