Biology subjects

Ewbank, J.

Publications and source records attributed to Ewbank, J..

5 recordsLinked to original sources

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↗

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

De novo long-read assembly of a complex animal genome

Eukaryotic genome assembly remains a challenge in part because of the prevalence of complex DNA repeats. This is a particularly acute problem for holocentric nematodes because of the large number of satellite DNA sequences found throughout their genomes. These have been recalcitrant to most genome sequencing methods. At the same time, many nematodes are parasites and some represent a serious threat to human health. There is a pressing need for better molecular characterization of animal and plant parasitic nematodes. The advent of long-read DNA sequencing methods offers the promise of resolving complex genomes. Using Nippostrongylus brasiliensis as a test case, applying improved base-calling algorithms and assembly methods, we demonstrate the feasibility of de novo genome assembly matching current community standards using only MinION long reads. In doing so, we uncovered an unexpected diversity of very long and complex DNA repeat sequences, including massive tandem repeats of tRNA genes. The method has the added advantage of preserving haplotypic variants and so has the potential to be used in population analyses.

genomics↗