Biology subjects

Smith, R. C.

Publications and source records attributed to Smith, R. C..

At least 19 recordsLinked to original sources

bioRxiv2026

Spontaneous neurotransmitter release is regulated by Unc-5

The spontaneous quantal release of single vesicles of neurotransmitter in the absence of an action potential is a universal feature of all neuronal chemical synapses. These miniature events have long been thought to be stochastic and unregulated, leading to measurement of their frequency as a widely employed estimate of the number of synaptic connections within neuronal networks. Here we show using high resolution live imaging of Drosophila adult glutamatergic synapses that the spontaneous release of neurotransmitter occurs from only a subset of synaptic release sites. We discover that the proportion of release sites participating in spontaneous neurotransmitter release is regulated by a novel synaptic function of the transmembrane signalling receptor Unc-5 which is heparan sulfate proteoglycan dependent, but Netrin independent. We show that synaptic Unc-5 forms a complex with the SNARE protein Syntaxin to regulate neurotransmitter release. The depletion of Unc-5 in adult synapses diminishes miniature events, inducing terminal degeneration and behavioural decline. Our results reveal that spontaneous neurotransmitter release is a singular, essential and independently regulated property of synapses that is critical for the structural integrity and behavioural contribution of synaptic connections.

neuroscience↗

bioRxiv2026

When clades collide: Genomic admixture in blacklegged ticks (Ixodes scapularis) from the Great Plains

Ixodes scapularis ticks transmit a number of pathogens important to human health, including Borrelia burgdorferi, the causative agent of Lyme disease. While I. scapularis is found across the Eastern United States, Lyme disease transmission is largely limited to the Northeast and Upper Midwest and is nearly absent in the South. This indicates that differences in northern versus southern clades of I. scapularis are associated with differences in Lyme disease transmission risk. I. scapularis is undergoing range expansion, including into the Great Plains region of the United States. Determining where I. scapularis populations in the Great Plains originated can inform future risk of Lyme disease transmission in this region. In this study, we use a population genomics framework to characterize diversity, structure, and B. burgdorferi infection rates of I. scapularis populations in the Great Plains region. We generated whole genome sequence data and single nucleotide polymorphism (SNP) datasets from I. scapularis ticks collected in Iowa, Kansas, Nebraska, and South Dakota to compare to publicly available data from across the species range. Our analysis of 200 I. scapularis SNP datasets indicated geographically well-defined populations that correspond to historical northern and southern ancestral clades of I. scapularis. Ticks from South Dakota, Iowa, and northeastern Nebraska are genetically similar populations from the Upper Midwest, while ticks from Kansas are more genetically similar to ticks from the Southeast. Ticks collected in the central eastern region of Nebraska, however, represent an evenly admixed population of both northern and southern genomic backgrounds. Analysis of B. burgdorferi reads from genomic datasets shows [~]50% infection rate in ticks from Iowa and northeastern Nebraska, whereas ticks from Kansas show no evidence of B. burgdorferi infection. Of note, evenly admixed ticks from the central eastern region of Nebraska also show no evidence of B. burgdorferi infection. These results provide further evidence that tick genomics may influence traits associated with B. burgdorferi infection status, and thus the potential for Lyme disease transmission. As the range of I. scapularis continues to expand, bringing historically isolated populations into contact, there is a clear need to understand the consequence of genomic admixture for B. burgdorferi transmission potential to inform future risk of Lyme disease in the United States.

genomics↗

bioRxiv2026

An integrated synthetic biology and robotics approach for neutralising landmines in post-war communities

Unexploded ordnances (UX.Os) and landmines endanger lives and hinder the economic progress of communities living in post-conflict zones. Currently, the primary method for clearing UX.Os relies on metal detection and manual removal of UX.Os - an expensive, time-consuming, and hazardous process. This study, derived from the 2024 EPFL iGEM project SYNPLODE, presents a new approach that integrates synthetic biology and aerial drone robotics, proposing a novel, end-to-end, safe, and efficient solution to address UX.Os. Starting from bacteria engineered to detect and degrade 2,4,6-trinitrotoluene (TNT), a common explosive in landmines, our solution is designed for three main tasks: detecting TNT and RDX, breaking these compounds down into non-explosive byproducts, and confirming explosive neutralisation. To deploy this solution safely in UXO-contaminated areas, we designed, built, and tested an aerial drone capable of spraying explosive-degrading bacteria. Combining synthetic biology, robotics, mathematical modelling, and affected community engagement, our solution aims to improve UXO and landmine clearance by offering a scalable and cost-effective approach for deactivating UX.Os without risking human lives.

synthetic biology↗

bioRxiv2025

FGF and MafB regulated cadherin expression drives lamina formation in the auditory hindbrain

The avian auditory brainstem contains specialized nuclei critical for sound localization, including the nucleus laminaris (nL), which forms as a single-cell-thick lamina essential for computing interaural time differences. Despite its functional importance, the molecular mechanisms guiding nL lamina formation have remained poorly understood. Here, we identify a signalling cascade involving FGF8, MafB, and cadherin-22 that orchestrates this morphogenetic process. We show that FGF8 is selectively expressed in the developing auditory hindbrain and correlates spatiotemporally with lamina formation in the nL. Disruption of FGF signalling--either via misexpression of FGF8 or dominant-negative FGFR1--perturbs the formation of the nL and alters cadherin-22 expression. In vitro culture experiments further reveal that nL lamination is sensitive to FGF8 dosage, with an optimal concentration required for both FGF8 and MafB expression and correct structural organization. We demonstrate that FGF8 induces MafB, which in turn regulates cadherin-22 expression. Functional disruption of cadherins impairs lamina formation and leads to reduced FGF8 expression, indicating a feedback loop between adhesion and signalling. Cadherin protein expression appears enriched in the dendrites of nL neurons and computational models--both static and dynamic--show that bipolar, dendrite-localized, adhesion can drive laminar architecture as the maximum adhesion configuration. These findings establish a novel molecular and biophysical mechanism for neuronal lamination in the vertebrate hindbrain, showing how local FGF signalling, transcriptional regulation, and dendritic adhesion converge to shape neural circuitry essential for sound localization.

developmental biology↗

bioRxiv2024

Exploring new dimensions of immune cell biology in Anopheles gambiae through genetic immunophenotyping

Mosquito immune cells, or hemocytes, are integral components of the innate immune responses that define vector competence. However, the lack of genetic resources has limited their characterization and our understanding of their functional roles in immune signaling. To overcome these challenges, we engineered transgenic Anopheles gambiae that express fluorescent proteins under the control of candidate hemocyte promoters. Following the characterization of five transgenic constructs through gene expression and microscopy-based approaches, we examine mosquito immune cell populations by leveraging advanced spectral imaging flow cytometry. Our results comprehensively map the composition of mosquito hemocytes, classifying them into twelve distinct populations based on size, granularity, ploidy, phagocytic capacity, and the expression of PPO6, SPARC, and LRIM15 genetic markers. Together, our novel use of morphological properties and genetic markers provides increased resolution into our understanding of mosquito hemocytes, highlighting the complexity and plasticity of these immune cell populations, while providing the foundation for deeper investigations into their roles in immunity and pathogen transmission.

genetics↗

bioRxiv2024

A genome-wide CRISPR screen in Anopheles mosquito cells identifies essential genes and required components of clodronate liposome function

Anopheles mosquitoes are the sole vector of human malaria, the most burdensome vector-borne disease worldwide. Strategies aimed at reducing mosquito populations and limiting their ability to transmit disease show the most promise for disease control. Therefore, gaining an improved understanding of mosquito biology, and specifically that of the immune response, can aid efforts to develop new approaches that limit malaria transmission. Here, we use a genome-wide CRISPR screening approach for the first time in mosquito cells to identify essential genes in Anopheles and identify genes for which knockout confers resistance to clodronate liposomes, which have been widely used in mammals and arthropods to ablate immune cells. In the essential gene screen, we identified a set of 1280 Anopheles genes that are highly enriched for genes involved in fundamental cell processes. For the clodronate liposome screen, we identified several candidate resistance factors and confirm their roles in the uptake and processing of clodronate liposomes through in vivo validation in Anopheles gambiae, providing new mechanistic detail of phagolysosome formation and clodronate liposome function. In summary, we demonstrate the application of a genome-wide CRISPR knockout platform in a major malaria vector and the identification of genes that are important for fitness and immune-related processes.

genetics↗

bioRxiv2024

Protection against Clostridioides difficile disease by a naturally avirulent C. difficile strain

Clostridioides difficile (C. difficile) strains belonging to the epidemic BI/NAP1/027 (RT027) group have been associated with increased transmissibility and disease severity. In addition to the major toxin A and toxin B virulence factors, RT027 strains also encode the CDT binary toxin. Our lab previously identified a toxigenic RT027 isolate, ST1-75, that is avirulent in mice despite densely colonizing the colon. Here, we show that co-infecting mice with the avirulent ST1-75 and virulent R20291 strains protects mice from colitis due to rapid clearance of the virulent strain and persistence of the avirulent strain. Although avirulence of ST1-75 is due to a mutation in the cdtR gene, which encodes a response regulator that modulates the production of all three C. difficile toxins, the ability of ST1-75 to protect against acute colitis is not directly attributable to the cdtR mutation. Metabolomic analyses indicate that the ST1-75 strain depletes amino acids more rapidly than the R20291 strain and supplementation with amino acids ablates ST1-75s competitive advantage, suggesting that the ST1-75 strain limits the growth of virulent R20291 bacteria by amino acid depletion. Since the germination kinetics and sensitivity to the co-germinant glycine are similar for the ST1-75 and R20291 strains, our results identify the rapidity of in vivo nutrient depletion as a mechanism providing strain-specific, virulence-independent competitive advantages to different BI/NAP1/027 strains. They also suggest that the ST1-75 strain may, as a biotherapeutic agent, enhance resistance to CDI in high-risk patients. ImportanceClostridioides difficile infections (CDI) are prevalent in healthcare settings and are associated with high recurrence rates. Therapies to prevent CDI, including recent FDA-approved live biotherapeutic products, are costly and have not been used to prevent primary infections. While a nontoxigenic C. difficile strain (NTCD-M3) protects against virulent CDI in animals and reduced CDI recurrence in a phase 2 clinical trial, protection against CDI recurrence in humans was variable and required high doses of the nontoxigenic strain. Here we show that an avirulent C. difficile isolate, ST1-75, efficiently outcompetes virulent C. difficile strains in mice when co-infected at a 1:1 ratio. Our data suggest that inter-strain competition results from ST1-75s more rapid depletion of amino acids than the virulent R20291 strain. Our study identifies inter-strain nutrient depletion as a potentially exploitable mechanism to reduce the incidence of CDI.

microbiology↗

bioRxiv2024

TNF signaling mediates cellular immune function and promotes malaria parasite killing in the mosquito Anopheles gambiae

Tumor Necrosis Factor- (TNF-) is a proinflammatory cytokine and a master regulator of immune cell function in vertebrates. While previous studies have implicated TNF signaling in invertebrate immunity, the roles of TNF in mosquito innate immunity and vector competence have yet to be explored. Herein, we confirm the identification of a conserved TNF- pathway in Anopheles gambiae consisting of the TNF- ligand, Eiger, and its cognate receptors Wengen and Grindelwald. Through gene expression analysis, RNAi, and in vivo injection of recombinant TNF-, we provide direct evidence for the requirement of TNF signaling in regulating mosquito immune cell function by promoting granulocyte midgut attachment, increased granulocyte abundance, and oenocytoid rupture. Moreover, our data demonstrate that TNF signaling is an integral component of anti-Plasmodium immunity that limits malaria parasite survival. Together, our data support the existence of a highly conserved TNF signaling pathway in mosquitoes that mediates cellular immunity and influences Plasmodium infection outcomes, offering potential new approaches to interfere with malaria transmission by targeting the mosquito host.

immunology↗

bioRxiv2024

Mosquito immune cells enhance dengue and Zika virus dissemination in Aedes aegypti

Mosquito-borne viruses cause more than 400 million annual infections and place over half of the worlds population at risk. Despite this importance, the mechanisms by which arboviruses infect the mosquito host and disseminate to tissues required for transmission are not well understood. Here, we provide evidence that mosquito immune cells, known as hemocytes, play an integral role in the dissemination of dengue virus (DENV) and Zika virus (ZIKV) in the mosquito Aedes aegypti. We establish that phagocytic hemocytes are a focal point for virus infection and demonstrate that these immune cell populations facilitate virus dissemination to the ovaries and salivary glands. Additional transfer experiments confirm that virus-infected hemocytes confer a virus infection to non-infected mosquitoes more efficiently than free virus in acellular hemolymph, revealing that hemocytes are an important tropism to enhance virus dissemination in the mosquito host. These data support a "trojan horse" model of virus dissemination where infected hemocytes transport virus through the hemolymph to deliver virus to mosquito tissues required for transmission and parallels vertebrate systems where immune cell populations promote virus dissemination to secondary sites of infection. In summary, this study significantly advances our understanding of virus infection dynamics in mosquitoes and highlights conserved roles of immune cells in virus dissemination across vertebrate and invertebrate systems.

microbiology↗

bioRxiv2024

Comprehensive analyses of a large human gut Bacteroidales culture collection reveal species and strain level diversity and evolution

Species of the Bacteroidales order are among the most abundant and stable bacterial members of the human gut microbiome with diverse impacts on human health. While Bacteroidales strains and species are genomically and functionally diverse, order-wide comparative analyses are lacking. We cultured and sequenced the genomes of 408 Bacteroidales isolates from healthy human donors representing nine genera and 35 species and performed comparative genomic, gene-specific, mobile gene, and metabolomic analyses. Families, genera, and species could be grouped based on many distinctive features. However, we also show extensive DNA transfer between diverse families, allowing for shared traits and strain evolution. Inter- and intra-specific diversity is also apparent in the metabolomic profiling studies. This highly characterized and diverse Bacteroidales culture collection with strain-resolved genomic and metabolomic analyses can serve as a resource to facilitate informed selection of strains for microbiome reconstitution.

microbiology↗

bioRxiv2023

Tick Innate Immune Responses to Hematophagy and Ehrlichia Infection at Single-Cell Resolution

Ticks rely on robust cellular and humoral immune responses to control microbial infection. However, several aspects of the ticks innate immune system remain uncharacterized, most notably that of the immune cells (called hemocytes), which are known to play a significant role in cellular and humoral responses toward microbes. Despite the importance of hemocytes in regulating microbial infection, our understanding of their basic biology and molecular mechanisms remains limited. Therefore, we believe that a more detailed understanding of the role of hemocytes in the interactions between ticks and tick-borne microbes is crucial to illuminate their function in vector competence and to help identify novel targets for developing new strategies to block tick-borne pathogen transmission. This study examined hemocytes from the lone star tick (Amblyomma americanum) at the transcriptomic level using the 10X genomics single-cell RNA sequencing platform to analyze hemocyte populations from unfed, partially blood-fed, and Ehrlichia chaffeensis-infected ticks. Our data exhibit the identification of twelve and nineteen distinct hemocyte populations, respectively, from uninfected and Ehrlichia-infected ticks. Our results show a significant increase of clusters representing granulocyte and oenocytoids populations with Ehrlichia infection. This work opens a new field of tick innate immunobiology to understand the role of hemocytes, particularly in response to prolonged blood-feeding (hematophagy) and tick-microbial interactions. SignificanceThe immune response of ticks plays a crucial role in their ability to survive and transmit pathogens. Hemocytes, the primary immune cells in arthropods, are key mediators of ticks immune defense and provide deep insights into immune responses to microbial infection. However, tick hemocytes cellular complexity and heterogeneity have posed challenges for comprehensive characterization. This study employed single-cell RNA sequencing (scRNA-seq) to profile tick hemocytes and elucidate their transcriptional diversity. We identified distinct subpopulations of hemocytes and characterized their unique gene expression profiles. We observed significant variation in immune-related gene expression between hemocyte subpopulations during hematophagy and in response to Ehrlichia infection, suggesting specialized functional roles. Our analysis revealed potential marker genes associated with specific hemocyte functions. Our study provides the first comprehensive single-cell atlas of tick hemocytes, shedding light on these cells molecular diversity and immune functions. The findings enhance our understanding of tick-host interactions and offer a step toward understanding arthropod immunobiology.

immunology↗

bioRxiv2023

co-opts phagocytic hemocytes for systemic dissemination in the Lone Star tick, .

Hematophagous arthropods can acquire and transmit several pathogens of medical importance. In ticks, the innate immune system is crucial in the outcome between vector-pathogen interaction and overall vector competence. However, the specific immune response(s) elicited by the immune cells known as hemocytes remains largely undefined in Ehrlichia chaffeensis and its competent tick vector, Amblyomma americanum. Here, we show that granulocytes, professional phagocytic cells, are integral in eliciting immune responses against commensal and pathogen infection. The chemical depletion of granulocytes led to decreased phagocytic efficiency of tissues-associated hemocytes. We demonstrate E. chaffeensis can infect circulating hemocytes, and both cell-free plasma and hemocytes from E. chaffeensis-infected ticks can establish Ehrlichia infection in recipient ticks. Lastly, we provide evidence to show granulocytes play a dual role in E. chaffeensis infection. Depleting granulocytic hemocytes increased Ehrlichia load in the salivary gland and midgut tissues. In contrast, granulocyte depletion led to a reduced systemic load of Ehrlichia. This study has identified multiple roles for granulocytic hemocytes in the control and systemic dissemination of E. chaffeensis infection.

immunology↗

bioRxiv2023

Virulence and genomic diversity among clinical isolates of ST1 (BI/NAP1/027) Clostridioides difficile

Clostridioides difficile (C. difficile), a leading cause of nosocomial infection, produces toxins that damage the colonic epithelium and results in colitis that varies from mild to fulminant. Variation in disease severity is poorly understood and has been attributed to host factors (age, immune competence and intestinal microbiome composition) and/or virulence differences between C. difficile strains, with some, such as the epidemic BI/NAP1/027 (MLST1) strain, being associated with greater virulence. We tested 23 MLST1(ST1) C. difficile clinical isolates for virulence in antibiotic-treated C57BL/6 mice. All isolates encoded a complete Tcd pathogenicity locus and achieved similar colonization densities in mice. Disease severity varied, however, with 5 isolates causing lethal infections, 16 isolates causing a range of moderate infections and 2 isolates resulting in no detectable disease. The avirulent ST1 isolates did not cause disease in highly susceptible Myd88-/- or germ-free mice. Genomic analysis of the avirulent isolates revealed a 69 base-pair deletion in the N-terminus of the cdtR gene, which encodes a response regulator for binary toxin (CDT) expression. Genetic deletion of the 69 base-pair cdtR sequence in the highly virulent ST1 R20291 C. difficile strain rendered it avirulent and reduced toxin gene transcription in cecal contents. Our study demonstrates that a natural deletion within cdtR attenuates virulence in the epidemic ST1 C. difficile strain without reducing colonization and persistence in the gut. Distinguishing strains on the basis of cdtR may enhance the specificity of diagnostic tests for C. difficile colitis.

microbiology↗

bioRxiv2022

Rickettsia parkeri Hijacks Tick Hemocytes to Manipulate Cellular and Humoral Transcriptional Responses

Blood-feeding arthropods rely on robust cellular and humoral immunity to control pathogen invasion and replication. Tick hemocytes produce factors that can facilitate or suppress microbial infection and pathogenesis. Despite the importance of hemocytes in regulating microbial infection, understanding of their basic biology and molecular mechanisms remains limited. Here we combined histomorphology and functional analysis to identify five distinct phagocytic and non-phagocytic hemocyte populations circulating within the Gulf Coast tick Amblyomma maculatum. Depletion of phagocytic hemocytes using clodronate liposomes revealed their function in eliminating bacterial infection. We provide the first direct evidence that an intracellular tick-borne pathogen, Rickettsia parkeri, infects phagocytic hemocytes in Am. maculatum to modify tick cellular immune responses. A massive RNA-seq dataset generated from hemocytes isolated from uninfected and R. parkeri-infected partially blood-fed ticks generated [~]40,000 differentially regulated transcripts, >11,000 of which were immune genes. Silencing two differentially regulated phagocytic immune marker genes (nimrod B2 and eater) significantly reduced hemocyte phagocytosis. Together, these findings represent a significant step forward in understanding how hemocytes regulate microbial homeostasis and vector competence.

immunology↗

bioRxiv2022

The PTEX pore component EXP2 is important for intrahepatic development during the Plasmodium liver stage

During vertebrate infection, obligate intracellular malaria parasites develop within a parasitophorous vacuole which constitutes the interface between the parasite and its hepatocyte or erythrocyte host cells. To transcend this barrier, Plasmodium spp. utilize a dual-function pore formed by EXP2 for nutrient transport and, in the context of the PTEX translocon, effector protein export across the vacuole membrane. While critical to blood stage survival, less is known about EXP2/PTEX function in the liver stage, although major differences in the export mechanism are indicated by absence of the PTEX unfoldase HSP101 in the intrahepatic vacuole. Here, we employed the glucosamine-activated glmS ribozyme to study the role of EXP2 during Plasmodium berghei liver stage development in hepatoma cells. Insertion of the glmS sequence into the exp2 3UTR enabled glucosamine-dependent depletion of EXP2 after hepatocyte invasion, allowing separation of EXP2 function during intrahepatic development from a recently reported role in hepatocyte invasion. Post-invasion EXP2 knockdown reduced parasite size and largely abolished expression of the mid to late liver stage marker LISP2. As an orthogonal approach to monitor development, EXP2-glmS parasites and controls were engineered to express nanoluciferase. Activation of glmS after invasion substantially decreased luminescence in hepatoma monolayers and in culture supernatants at later time points corresponding with merosome detachment that marks the culmination of liver stage development. Collectively, our findings extend the utility of the glmS ribozyme to study protein function in the liver stage and reveal EXP2 is important for intrahepatic parasite development, indicating PTEX components also function at the hepatocyte-parasite interface.

microbiology↗

bioRxiv2022

Semi-field and surveillance data define the natural diapause timeline for Culex pipiens across the United States

Culex pipiens is a globally-distributed mosquito of medical and veterinary importance, serving as a primary vector of West Nile virus (WNV). To survive winter, female Cx. pipiens mosquitoes undergo adult reproductive diapause initiated by photoperiod and temperature cues. While well-studied under laboratory conditions, the environmental signals that promote Cx. pipiens diapause induction in natural settings are less understood. Here, we evaluate Cx. pipiens in laboratory and semi-field studies to examine diapause induction, defining an approximate timeline beginning in late-August where mosquitoes become receptive to diapause. Using gravid (reproductive) mosquito surveillance data as a proxy for adult diapause incidence for locations across the United States (California, Colorado, Connecticut, Illinois, Iowa, Minnesota, Pennsylvania, and Virginia), we demonstrate consistent population declines coinciding with periods of diapause receptivity except in hybridization zones where Cx. quinquefasciatus is present, suggesting that Culex population genetics can significantly impact end-season population trends. Together, this study defines a window for diapause induction across the United States, shaped by temperature, latitude, elevation, and mosquito population genetics. Coinciding with the cessation of WNV activity, these data can have important implications for mosquito control, where targeted efforts prior to diapause induction can decrease mosquito populations and WNV overwintering to reduce mosquito-borne disease incidence the following season.

ecology↗

bioRxiv2022

Extracellular vesicles secreted by Brugia malayi microfilariae modulate the melanization pathway in the mosquito host

Vector-borne, filarial nematode diseases represent a significant and affecting disease burden in humans, domestic animals, and livestock worldwide. Parasitic filarial nematodes require both an intermediate (vector) host and a definitive (mammalian) host during the course of their life cycle. In either host, the nematode must evade the host elicited immune response in order to develop and establish infection. There is direct evidence of parasite-derived immunomodulation in mammals, however, there is less evidence of parasite immunomodulation of the vector host. We have previously reported that all life stages of Brugia malayi, a causative agent of lymphatic filariasis, secrete extracellular vesicles (EVs). Here we investigate the immunomodulatory effects of microfilariae derived EVs on the vector host Aedes aegypti. RNA-seq analysis of an A. aegypti cell line treated with B. malayi microfilariae EVs showed differential expression of both mRNAs and miRNAs, some with roles in immune regulation. One downregulated gene, AAEL002590, identified as a serine protease, was shown to have direct involvement in the phenoloxidase (PO) cascade through analysis of PO activity. Similarly, injection of adult female mosquitoes with B. malayi microfilariae EVs validated these results in vivo, eliciting a downregulation of the AAEL002590 transcript and a significant reduction in PO activity. Our data indicates that parasite-derived EVs are capable of interfering with critical immune responses in the vector host, particularly immune responses such as melanization that target extracellular parasites. In addition, this data provides novel targets for transmission control strategies for LF and other parasitic diseases. Author SummaryVector-borne, filarial nematode diseases represent a significant and affecting disease burden in humans, domestic animals and livestock worldwide. Parasitic nematodes must evade the elicited immune response of their hosts in order to develop and establish infection. While there is evidence for immunomodulation of the mammalian host, the mechanism of this immunomodulation is not fully clear and there is limited evidence for immunomodulation of the vector host. Here we have shown that parasite-derived extracellular vesicles are effector structures for immunomodulation of the vector host. In particular, we have identified that parasite-derived extracellular vesicles can interfere with critical mosquito immune responses against parasites. This data provides insight into parasite biology and novel targets for transmission control strategies for parasitic diseases.

immunology↗

bioRxiv2021

Spastic paraplegia protein ortholog, reticulon-like 1, governs presynaptic ER organization and Ca2+ dynamics

Neuronal endoplasmic reticulum (ER) appears continuous throughout the cell. Its shape and continuity are influenced by ER-shaping proteins, mutations in which can cause distal axon degeneration in Hereditary Spastic Paraplegia (HSP). We therefore asked how loss of Rtnl1, a Drosophila ortholog of the human HSP gene RTN2 (SPG12), which encodes an ER-shaping protein, affects ER organization and the function of presynaptic terminals. Loss of Rtnl1 depleted ER membrane markers at Drosophila presynaptic motor terminals, and appeared to deplete narrow tubular ER while leaving cisternae largely unaffected, thus suggesting little change in resting Ca2+ storage capacity. Nevertheless, these changes were accompanied by major reductions in activity-evoked Ca2+ fluxes in the cytosol, ER lumen, and mitochondria, as well as reduced evoked and spontaneous neurotransmission. We found that reduced STIM-mediated ER-plasma membrane contacts underlie presynaptic Ca2+ defects in Rtnl1 mutants. Our results show the importance of ER architecture in presynaptic physiology and function which are therefore potential factors in the pathology of HSP.

neuroscience↗