Couillault C et al. (2002) Infect Immun "Diverse bacteria are pathogens of Caenorhabditis elegans."

Couillault C, Ewbank JJ

[Infect Immun, 2002]

Practically and ethically attractive as model systems, invertebrate organisms are increasingly recognized as relevant for the study of bacterial pathogenesis. We show here that the nematode Caenorhabditis elegans is susceptible to a surprisingly broad range of bacteria and may constitute a useful model for the study of both pathogens and symbionts.

Couillault C et al. (2012) Virulence "A UPR-independent infection-specific role for a BiP/GRP78 protein in the control of antimicrobial peptide expression in C. elegans epidermis."

Couillault C, Ewbank J, Fourquet P, Pophillat M

[Virulence, 2012]

The nematode C. elegans responds to infection by the fungus Drechmeria coniospora with a rapid increase in the expression of antimicrobial peptide genes. To investigate further the molecular basis of this innate immune response, we took a two-dimensional difference in-gel electrophoresis (2D-DIGE) approach to characterize the changes in host protein that accompany infection. We identified a total of 68 proteins from differentially represented spots and their corresponding genes. Through class testing, we identified functional categories that were enriched in our proteomic data set. One of these was "protein processing in endoplasmic reticulum," pointing to a potential link between innate immunity and endoplasmic reticulum function. This class included HSP-3, a chaperone of the BiP/GRP78 family known to act coordinately in the endoplasmic reticulum with its paralog HSP-4 to regulate the unfolded protein response (UPR). Other studies have shown that infection of C. elegans can provoke a UPR. We observed, however, that in adult C. elegans infection with D. coniospora did not induce a UPR, and conversely, triggering a UPR did not lead to an increase in expression of the well-characterized antimicrobial peptide gene nlp-29. On the other hand, we demonstrated a specific role for hsp-3 in the regulation of nlp-29 after infection that is not shared with hsp-4. Epistasis analysis allowed us to place hsp-3 genetically between the Tribbles-like kinase gene nipi-3 and the protein kinase C delta gene tpa-1. The precise function of hsp-3 has yet to be determined, but these results uncover a hitherto unsuspected link between a BiP/GRP78 family protein and innate immune signaling.

Couillault C et al. (2004) Nat Immunol "TLR-independent control of innate immunity in Caenorhabditis elegans by the TIR domain adaptor protein TIR-1, an ortholog of human SARM."

Couillault C, Reboul J, Ewbank J, Pujol N, Kohara Y, Sabatier L, Guichou JF

[Nat Immunol, 2004]

Both plants and animals respond to infection by synthesizing compounds that directly inhibit or kill invading pathogens. We report here the identification of infection-inducible antimicrobial peptides in Caenorhabditis elegans. Expression of two of these peptides, NLP-29 and NLP-31, was differentially regulated by fungal and bacterial infection and was controlled in part by tir-1, which encodes an ortholog of SARM, a Toll-interleukin 1 receptor (TIR) domain protein. Inactivation of tir-1 by RNA interference caused increased susceptibility to infection. We identify protein partners for TIR-1 and show that the small GTPase Rab1 and the f subunit of ATP synthase participate specifically in the control of antimicrobial peptide gene expression. As the activity of tir-1 was independent of the single nematode Toll-like receptor, TIR-1 may represent a component of a previously uncharacterized, but conserved, innate immune

Lamitina T et al. (2012) Virulence "To UPR... and beyond! A new role for a BiP/GRP78 protein in the control of antimicrobial peptide expression in C. elegans epidermis."

Lamitina T, Chevet E

[Virulence, 2012]

The fungal pathogen Drechmeria coniospora infects C. elegans and elicits an innate immune response mediated, in part, by the induction of antimicrobial peptides in the epidermis. The signaling pathways controlling this phenomenon remain to be fully characterized. In this issue of Virulence, Couillault and colleagues use both proteomics and genetics to discover an unexpected role for the unfolded protein response (UPR) target chaperone BiP/GRP78/hsp-3 in the control of fungal infection-induced antimicrobial peptide expression in C. elegans. Although the expression of hsp-3 is regulated by the UPR, Couillault and colleagues describe a novel signaling role for this BiP/GRP78 homolog.

Daniel Wong et al. (2005) International Worm Meeting "How specific is the response of C. elegans to bacterial infection?"

Daniel Wong, Jonathan Ewbank

[International Worm Meeting, 2005]

Many different pathogens have been described for worms (1). Using the cDNA microarrays developed by Yuji Kohara, we have shown that the fungus Drechmeria coniospora and bacterium Serratia marcescens provoke very different responses at the transcriptional level (2,3). We are now using whole genome long oligonucleotide microarrays, to examine systematically the host response during infection with a diverse selection of microbes. These include natural pathogens of the worm, opportunistic pathogens known to have a general, adverse impact on human health and highly infectious organisms classified as potential biowarfare agents. We thereby expect to identify both genes that are up-regulated irrespective of the infectious agent, and pathogen-specific genes. These studies will contribute to our understanding of the specificity of innate immune defences in the worm.1. Pradel, E. & Ewbank, J. J. Genetic models in pathogenesis. Annu Rev Genet 38, 347-63 (2004).2. Mallo, G. V. et al. Curr Biol 12, 1209-14 (2002).3. Couillault, C. et al. Nat Immunol 5, 488-494 (2004).

Robbie Rae et al. (2007) International Worm Meeting "Susceptibility and immune response of Pristionchus species exposed to pathogenic bacteria."

Ralf J. Sommer, Robbie Rae

[International Worm Meeting, 2007]

Caenorhabditis elegans is susceptible to infection by bacteria associated with insect parasitic nematodes such as Photorhabdus luminescens and Xenorhabdus nematophila (Couillault and Ewbank, 2002). We exposed several species of Pristionchus (Pristionchus pacificus California and Washington strains, Pristionchus entomophagus and Pristionchus maupasi) to P. luminescens, X. nematophila and Moraxella osloensis. Mortality was assessed over a 20-day period and compared with C. elegans. We hypothesized that Pristionchus was not susceptible to bacterial infection as it lacks a grinder and bacteria will pass through the gut alive and intact. In a second experiment we investigated the possible role of glutathione produced by Pristionchus to detoxify and protect the nematode from bacterial pathogens. Glutathione transferase proteins were extracted from nematodes exposed to pathogenic and non-pathogenic bacteria and were analysed using SDS-PAGE, 2D Electrophoresis and identified using MALDI-TOF. Total glutathione produced by the nematodes was also examined and compared with C. elegans. Couillault, C. and Ewbank, J.J. 2002. Diverse bacteria are pathogens of Caenorhabditis elegans. Infection and Immunity, 4705-4707.

Filippopoulou K et al. (2021) Biol Open "Multiple neural bHLHs ensure the precision of a neuronal specification event in C. elegans."

Bertrand V, Couillault C, Filippopoulou K

[Biol Open, 2021]

Neural bHLH transcription factors play a key role in the early steps of neuronal specification in many animals. We have previously observed that the Achaete-Scute HLH-3, the Olig HLH-16 and their binding partner the E protein HLH-2 activate the terminal differentiation program of a specific class of cholinergic neurons, AIY, in C. elegans. Here we identify a role for a fourth bHLH, the Neurogenin NGN-1, in this process, raising the question of why so many neural bHLHs are required for a single neuronal specification event. Using quantitative imaging we show that the combined action of different bHLHs is needed to activate the correct level of expression of the terminal selector transcription factors TTX-3 and CEH-10 that subsequently initiate and maintain the expression of a large battery of terminal differentiation genes. Surprisingly, the different bHLHs have an antagonistic effect on another target, the proapoptotic BH3-only factor EGL-1, normally not expressed in AIY and otherwise detrimental for its specification. We propose that the use of multiple neural bHLHs allows robust neuronal specification while, at the same time, preventing spurious activation of deleterious genes.

Filippopoulou, K. et al. (2019) International Worm Meeting "Janus-faced proneural factors: neuronal fate drivers and cell killers."

Couillault, C., Bertrand, V., Filippopoulou, K.

[International Worm Meeting, 2019]

During nervous system development, diverse neurons with specific identities are generated. This process is regulated by terminal selector transcription factors that are initially activated in newly generated postmitotic neurons, and regulate batteries of terminal differentiation genes responsible for the specific functions of the neuron. In C. elegans the set of neurons generated is invariant, therefore this process has to be strictly controlled. We have observed that in the AIY cholinergic neurons the differentiation program is initiated by several proneural bHLH transcription factors belonging to different families (achaete-scute, beta3 and neurogenins). By quantifying mRNA levels (with smFISH) and protein levels (with endogenous CRISPR tagging) we are analyzing how the combination of different bHLH ensures an accurate level of activation for the terminal selector transcription factors (TTX-3 and CEH-10). In addition, we have observed that these proneural bHLH factors have antagonistic roles in preventing apoptosis of the AIY neurons. We propose that the use of several proneural bHLH factors may fine-tune the initial level of terminal selector transcription factors while preventing cell death of the neurons.

Katja Ziegler et al. (2007) International Worm Meeting "A Sodium:Neurotransmitter symporter Family protein required for the induction of antimicrobial peptides in C.elegans."

Jonathan Ewbank, Nathalie Pujol, Katja Ziegler

[International Worm Meeting, 2007]

C. elegans responds to infection with the nematophagous fungus Drechmeria coniospora by up-regulating the expression of antimicrobial peptides including certain NLPs (neuropeptide-like proteins) and CNCs (Caenorhabditis bacteriocins) (1). We have generated a reporter strain containing the promoter of the antimicrobial peptide gene, nlp-29, fused to gfp. This results in a strain in which green fluorescence is highly induced after infection with D. coniospora. Coupled with the Union Biometrica BioSort, this provides us with a valuable tool to study infection-dependent induction in a qualitative and quantitative fashion. Using this strain and a direct visual screen following EMS mutagenesis, we identified 5 Nipi (no induction of peptide after Drechmeria infection) mutants (see abstracts by Pujol et al., Zugasti et al.). This study describes the isolation, characterization and SNP mapping of nipi-2. The mutant was found to carry a mutation in a conserved residue of a member of the sodium-dependent neurotransmitter transporter family in C. elegans. We are currently further characterizing this SNF protein and investigating its role in the induction of nlp-29 that follows infection. Progress will be reported at the meeting. 1.Couillault, C., Pujol, N., Reboul, J., Sabatier, L., Guichou, J. F., Kohara, Y. & Ewbank, J. J. (2004) Nat Immunol 5, 488-494. .

Labrousse AM et al. (2000) Curr Biol "Caenorhabditis elegans is a model host for Salmonella typhimurium."

Ewbank JJ, Chauvet S, Couillault C, Kurz CL, Labrousse AM

[Curr Biol, 2000]

The idea of using simple, genetically tractable host organisms to study the virulence mechanisms of pathogens dates back at least to the work of Darmon and Depraitere [1]. They proposed using the predatory amoeba Dictyostelium discoideum as a model host, an approach that has proved to be valid in the case of the intracellular pathogen Legionella pneumophila [2]. Research from the Ausubel laboratory has clearly established the nematode Caenorhabditis elegans as an attractive model host for the study of Pseudomonas aeruginosa pathogenesis [3]. P. aeruginosa is a bacterium that is capable of infecting plants, insects and mammals. Other pathogens with a similarly broad host range have also been shown to infect C. elegans [3,4]. Nevertheless, the need to determine the universality of C. elegans as a model host, especially with regards pathogens that have a naturally restricted host specificity, has rightly been expressed [5]. We report here that the enterobacterium Salmonella typhimurium, generally considered to be a highly adapted pathogen with a narrow range of target hosts [6], is capable of infecting and killing C. elegans. Furthermore, mutant strains that exhibit a reduced virulence in mammals were also attenuated for their virulence in C. elegans, showing that the nematode may constitute a useful model system for the study of this important human pathogen.