Biology subjects

Pujol, N.

Publications and source records attributed to Pujol, N..

11 recordsLinked to original sources

bioRxiv2025

A novel membrane contact site in vestibular hair cells

The mammalian vestibular system has two types of sensory receptor hair cells (HCs), each with different neurotransmission mechanisms. Type II HCs use ribbon synapses to transmit neurotransmitters like glutamate to afferent neurons. On the other hand, type I HCs are nearly engulfed by a calyceal afferent ending and also form ribbon synapses. These HCs regulate afferent activity through non-quantal transmission (NQT), which is faster than classic neurotransmitter release and may play a key role in stabilizing vision and balance during rapid head movements. Here, we describe a novel striated contact, present between the mouse type I HC and its calyceal afferent ending, and intimately associated with atypical plasma membrane-apposed (PMA) mitochondria. This distinctive arrangement has the potential to serve or modulate NQT.

neuroscience↗

bioRxiv2024

Pathogen threat proximity shapes host extracellular vesicle production in pre-infection response

Extracellular vesicles (EVs) play a crucial role in immune responses, yet it remains unclear whether pathogen metabolites alone can stimulate EV production prior to infection. Using Caenorhabditis elegans, we investigate this question through the lens of exophers - large, evolutionarily conserved EVs known to enhance proteostasis, extend lifespan, and improve reproductive fitness. Our study uncovers distinct regulatory mechanisms driving EV production in response to pathogen-derived volatile metabolites and non-volatile secretome, providing insights into host-pathogen signaling before physical interaction. We reveal a sophisticated network that adjusts EV production based on pathogen proximity: non-volatile secretome (including tripeptide Ile-Pro-Pro), signaling an immediate threat, activate immune-dependent EV pathways, while volatile metabolites, forewarning potential danger, initiate immunity-independent exopher production. Both responses rely on sensory neurons, with ASK, ADL, and AWC neurons playing central roles in each, and additional input from ASI, AWB, and ASH neurons specifically enhancing non-volatile secretome-induced EV production. Downstream signal integration is mediated by a circuit involving the RMG hub and AIB/AIA interneurons, with the AIB-specific NPR-9 receptor playing a critical role. Molecularly, we identified multiple GPCRs, including SRI-19, SRI-36/39, and SRR-6, as crucial for the non-volatile response, and revealed that SRR-6 functions in the intestine to regulate muscle exopher production, demonstrating a novel gut-muscle signaling axis. Notably, exposure to volatile pathogen metabolites significantly boosts offspring fitness during infection in SRI-19-dependent manner, albeit at the cost of maternal survival when conditions are being harsher. Thus, our study shows that C. elegans distinguishes pathogen proximity through compound types, activating EV-dependent physiological responses tailored to either immediate or anticipated threats to optimize survival across generations.

physiology↗

bioRxiv2024

A defining member of the new cysteine-cradle family is a transient aECM protein involved in signalling skin damage

Apical extracellular matrices (aECMs) act as crucial barriers, and communicate with the epidermis to trigger protective responses following injury or infection. In Caenorhabditis elegans, the skin aECM, the cuticle, is produced by the epidermis and is decorated with periodic circumferential furrows. We previously showed that mutants lacking cuticle furrows exhibit persistent immune activation (PIA). In a genetic suppressor screen, we identified spia-1 as a key gene downstream of furrow collagens and upstream of immune signalling. spia-1 expression oscillates during larval development, peaking between each moult together with patterning cuticular components. It encodes a secreted protein that localises to furrows. SPIA- 1 shares a novel cysteine-cradle domain with other aECM proteins. SPIA-1 mediates immune activation in response to furrow loss and is proposed to act as a sensor of cuticle damage. This research provides a molecular insight into intricate interplay between cuticle integrity and epidermal immune activation in C. elegans. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=70 SRC="FIGDIR/small/589058v2_ufig1.gif" ALT="Figure 1"> View larger version (18K): org.highwire.dtl.DTLVardef@152abadorg.highwire.dtl.DTLVardef@85169eorg.highwire.dtl.DTLVardef@18ff2d3org.highwire.dtl.DTLVardef@18f31d0_HPS_FORMAT_FIGEXP M_FIG C_FIG

developmental biology↗

bioRxiv2024

zIncubascope: long-term quantitative imaging of multi-cellular assemblies inside an incubator

Recent advances in bioengineering have made it possible to develop increasingly complex biological systems to recapitulate organ functions as closely as possible in vitro. Monitoring the assembly and growth of multi-cellular aggregates, micro-tissues or organoids and extracting quantitative information is a crucial but challenging task required to decipher the underlying morphogenetic mechanisms. We present here an imaging platform designed to be accommodated inside an incubator which provides high-throughput monitoring of cell assemblies over days and weeks. We exemplify the capabilities of our system by investigating human induced pluripotent stem cells (hiPSCs) enclosed in spherical capsules, hiPSCs in tubular capsules and yeast cells in spherical capsules. Combined with a customized pipeline of image analysis, our solution provides insight into the impact of confinement on the morphogenesis of these self-organized systems.

bioengineering↗

bioRxiv2021

Meisosomes, folded membrane platforms, link the epidermis to the cuticle in C. elegans

Apical extracellular matrices (aECMs) form a physical barrier to the environment. In C. 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 might 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.

cell biology↗

bioRxiv2021

An integrated analysis tool reveals intrinsic biases in gene set enrichment

Generating meaningful interpretations of gene lists remains a challenge for all large-scale studies. Many approaches exist, often based on evaluating gene enrichment among pre-determined gene classes. Here, we conceived and implemented yet another analysis tool (YAAT), specifically for data from the widely-used model organism C. elegans. YAAT extends standard enrichment analyses, using a combination of co-expression data and profiles of phylogenetic conservation, to identify groups of functionally-related genes. It additionally allows class clustering, providing inference of functional links between groups of genes. We give examples of the utility of YAAT for uncovering unsuspected links between genes and show how the approach can be used to prioritise genes for in-depth study. Our analyses revealed several limitations to the meaningful interpretation of gene lists, specifically related to data sources and the "universe" of gene lists used. We hope that YAAT will represent a model for integrated analysis that could be useful for large-scale exploration of biological function in other species.

bioinformatics↗

bioRxiv2020

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

Animals 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, potentially as a consequence of a host surveillance mechanism, increases STA-2 levels in the nucleus, modifies the nucleolus, and 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.

microbiology↗

bioRxiv2020

Antimicrobial peptides signal need for sleep from peripheral wounds to the nervous system

Wounding triggers a protective innate immune response that includes the production of antimicrobial peptides and increased sleep. Little is known, however, about how peripheral wounds signal need for sleep to the nervous system. We found that during C. elegans larval molting, a tolloid/BMP-1-like protein promotes sleep through an epidermal innate immune pathway and the expression of more than a dozen antimicrobial peptide (AMP) genes. In the adult, epidermal injury activates innate immunity and turns up AMP production to trigger sleep. We show for one AMP, NLP-29, that it acts through the neuropeptide receptor NPR-12 in neurons that depolarize the sleep-active RIS neuron to induce sleep. Sleep in turn increases the chance of surviving injury. Thus, we found a novel mechanism by which peripheral wounds signal to the nervous system to increase protective sleep. Such a long-range somnogen signaling function of AMPs might also boost sleep in other animals including humans. Highlights- Gain-of-function mutation in the tolloid/BMP-1-like NAS-38 protein increases sleep - NAS-38 activates innate immunity pathways to ramp up STAT-dependent antimicrobial peptide (AMP) expression - Wounding increases sleep through the innate immune response and AMPs - Antimicrobial peptides are long-range somnogens that act through neuronal neuropeptide receptors to depolarize a sleep-active neuron - Sleep increases the chance to survive injury Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=83 HEIGHT=200 SRC="FIGDIR/small/183806v1_ufig1.gif" ALT="Figure 1"> View larger version (20K): org.highwire.dtl.DTLVardef@213601org.highwire.dtl.DTLVardef@60955dorg.highwire.dtl.DTLVardef@ee1e4corg.highwire.dtl.DTLVardef@1074a86_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2019

Microtubule plus-end dynamics link wound repair to the innate immune response

As a first line of defence against the environment, the epidermis protect animals from infection and physical damage. In C. elegans, wounding the epidermal epithelium triggers both an immune reaction and a repair response. Exactly how these are controlled, and the degree to which they are inter-connected remains unclear. To address these questions, we established a simple system for simultaneously inflicting precise laser wounds and imaging at high spatial and temporal resolution. We show that in C. elegans, wounding provokes a rapid sealing of the plasma membrane, involving reorganisation of phosphatidylinositol 4,5- bisphosphate domains. This is followed by a radial recruitment at the wound site of EBP-2/EB1, a protein that binds the plus ends of microtubules. EB1 recruitment is accompanied by a reorganisation of microtubules, required for the subsequent recruitment of actin and wound closure. It is also required for the directed trafficking towards the site of injury of the key signalling protein SNF-12. In the absence of SNF-12 recruitment, there is an abrogation of the immune response. Our results suggest that microtubule dynamics coordinate the cytoskeletal changes required for wound repair and the concomitant activation of the innate immune response.

cell biology↗

bioRxiv2017

Modulatory upregulation of an insulin peptide gene by different pathogens in C. elegans

When an animal is infected, its innate immune response needs to be tightly regulated across tissues and coordinated with other aspects of organismal physiology. Previous studies with Caenorhabditis elegans have demonstrated that insulin-like peptide genes are differentially expressed in response to different pathogens. They represent prime candidates for conveying signals between tissues upon infection. Here, we focused on one such gene, ins-11 and its potential role in mediating cross-tissue regulation of innate immune genes. While diverse bacterial intestinal infections can trigger the up-regulation of ins-11 in the intestine, we show that epidermal infection with the fungus Drechmeria coniospora triggers an upregulation of ins-11 in the epidermis. Using the Shigella virulence factor OpsF, a MAP kinase inhibitor, we found that in both cases, ins-11 expression is controlled cell autonomously by p38 MAPK, but via distinct transcription factors, STA-2/STAT in the epidermis and HLH-30/TFEB in the intestine. We established that ins-11, and the insulin signaling pathway more generally, are not involved in the regulation of antimicrobial peptide gene expression in the epidermis. The up-regulation of ins-11 in the epidermis does, however, affect intestinal gene expression in a complex manner, and has a deleterious effect on longevity. These results support a model in which insulin signaling, via ins-11, contributes to the coordination of the organismal response to infection, influencing the allocation of resources in an infected animal.

genetics↗

bioRxiv2017

Evolutionary plasticity in the innate immune function of Akirin

Eukaryotic gene expression requires the coordinated action of transcription factors, chromatin remodelling complexes and RNA polymerase. The conserved nuclear protein Akirin plays a central role in immune gene expression in insects and mammals, linking the SWI/SNF chromatin-remodelling complex with the transcription factor NF{kappa}B. Although nematodes lack NF{kappa}B, Akirin is also indispensable for the expression of defence genes in the epidermis of Caenorhabditis elegans following natural fungal infection. Through a combination of reverse genetics and biochemistry, we discovered that in C. elegans Akirin has conserved its role of bridging chromatin-remodellers and transcription factors, but that the identity of its functional partners is different since it forms a physical complex with NuRD proteins and the POU-class transcription factor CEH-18. In addition to providing a substantial step forward in our understanding of innate immune gene regulation in C. elegans, our results give insight into the molecular evolution of lineage-specific signalling pathways.

immunology↗