Biology subjects

Marks, N. J.

Publications and source records attributed to Marks, N. J..

10 recordsLinked to original sources

bioRxiv2025

Serotonin signaling modulates growth and motility in juvenile Fasciola hepatica

Fasciola hepatica causes fasciolosis, a parasitic disease that poses significant animal and human health challenges. Control relies on flukicides, most of which are adulticides, with only triclabendazole effective against the pathogenic migratory juvenile. Classical neurotransmitter pathways are widely targeted by anthelmintics yet remain underexplored for flukicide development. Here we explore the importance of serotonin (5-HT) signaling in juvenile fluke. In silico analyses confirmed all F. hepatica life stages express a complete 5-HT signaling pathway encompassing genes encoding proteins for 5-HT synthesis, transport, and reuptake, as well as five putative 5-HT G protein-coupled receptors (GPCRs). Homology and binding motif analyses supported the presence of two 5-HT1 (Fh5HT1A, Fh5HT1B) and three 5-HT7 (Fh5HT7A, -7B, -7C) GPCRs. Immunocytochemistry and in situ hybridization revealed widespread neuronal expression of 5-HT, its synthetic enzyme tryptophan hydroxylase (FhTPH), and the GPCR Fh5HT7C. 5-HT addition stimulated juvenile fluke motility; consistent with this observation, serotonin reuptake inhibition, which causes 5-HT persistence at synaptic junctions, also enhanced juvenile movement. Silencing of FhTPH, a key enzyme in 5-HT synthesis, blunted juvenile motility, a phenotype reversed by the addition of 5-HT. Silencing the fluke vesicular monoamine transporter (FhVMAT), which packages 5-HT into synaptic vesicles, reduced juvenile motility, whilst silencing the 5-HT reuptake transporter (FhSERT) which recycles synaptic 5-HT increased juvenile motility and growth, consistent with 5-HT accumulation enhancing effects. Whilst combinatorial silencing of Fh5HT1 receptors reduced fluke motility, silencing Fh5HT7 receptors led to a greater reduction in motility. Exogenous addition of 5-HT partially rescued motility deficits of juveniles with silenced Fh5HT1 receptors, but 5-HT excitation was abolished in Fh5HT7-RNAi juveniles, exposing their importance to fluke motility. Notably, sustained 5-HT exposure promoted juvenile growth, but these effects were not blunted by receptor-RNAi. The findings emphasize a central role of serotonin signaling in both juvenile motility and growth, exposing novel aspects of receptor function and encouraging therapeutic exploitation for liver fluke control. Author SummaryThe liver fluke, Fasciola hepatica, causes fasciolosis, a neglected tropical disease that poses a significant burden on human and animal health. There is no vaccine for fasciolosis and treatment relies on a single drug, triclabendazole, to control the early stages of infection which cause liver pathology whilst migrating through the mammalian host. Single drug reliance has increased the incidence of drug resistance in both human and animal populations, such that there is a pressing need for the characterization of novel drug targets and development of new anthelmintics targeting liver fluke. The focus of this research is to examine the role of the serotonin signaling system of liver fluke, bridging a gap in knowledge to enable the exploitation of this signaling pathway for flatworm drug development. Here, bioinformatic analysis has characterized the pathway components and receptors in multiple clinically relevant flatworm parasite species. Chemical and functional genomic methods have been used to prove the integral function of serotonin in liver fluke biology, regulating motility and growth, both essential for parasite infection and survival. This work provides data that help validate the serotonergic system of liver fluke as a potential target for future anthelmintic development.

molecular biology↗

bioRxiv2025

Polo-like kinase 1 regulates growth in juvenile Fasciola hepatica

Fasciola sp. (liver fluke) are parasitic flatworms that impose a significant burden on the agri-food industry and human health. Immature worms can cause severe damage to the liver as they migrate towards the bile ducts, and yet there is only a single drug to treat this pathogenic life stage, driving the need to identify targets for novel flukicides. Given their crucial role in the growth/development of immature Fasciola hepatica, neoblast-like stem cells are an attractive source of new flukicide targets. Kinases are a hugely diverse group of phosphorylating enzymes with key roles in almost all cellular processes. Kinase dysregulation can result in the development of cancerous cells/tissues, linking many to cell cycle-associated proliferation and growth. Here, we annotate the F. hepatica kinome, identifying 271 putative protein kinases, representing around 1.6% of predicted F. hepatica protein-coding genes with family proportions similar to those of other parasitic flatworms. Many of these kinases, such as polo-like kinase 1 (fhplk1), are upregulated in immature worms undergoing rapid growth and development, a process underpinned by the proliferation of neoblast-like stem cells. RNA interference (RNAi)-mediated silencing of fhplk1 in juvenile liver fluke reduced growth and cell proliferation, suggesting a conserved role within the cell-cycle; the cessation of stem cell proliferation persisted for at least a week following fhplk1-RNAi. A PLK inhibitor (BI 2536) was shown to phenocopy the fhplk1-RNAi phenotype in a dose-dependent manner, supporting the feasibility of targeting F. hepatica neoblast-like cells through kinase inhibitors. Transcriptomic analysis of fhplk1-RNAi juveniles revealed 946 downregulated genes, principally associated with the cell cycle or ribosomes. Over 80 of these downregulated genes were also downregulated following juvenile F. hepatica irradiation, supporting roles for these kinases in neoblast-like stem cells, and marking them as putative targets for control. Among the 1244 upregulated genes in fhplk1-RNAi juvenile worms were many neurotransmitters, receptors and ion channels, exposing the apparent upregulation of diverse inter-cellular signalling systems. While many neurotransmitter pathways promote proliferation in mammalian systems the interaction between neoblast-like stem cells and neuronal signalling in parasitic flatworms remains elusive. Here, the transcriptomic response of fhplk1-RNAi juveniles supports a link between neoblast-like stem cell driven growth/development and neuronal signalling. Author SummaryThe liver fluke is a parasitic flatworm which causes disease in livestock and humans around the world. While establishing the infection, immature liver fluke migrate through the host liver causing significant damage. Unfortunately, only one drug is currently recommended for treatment of these immature worms, though resistance to this drug is now widespread and exposes the pressing need to develop novel drugs. As worms migrate through the liver, they undergo growth and development which is facilitated by proliferating stem cells. These neoblast-like cells are akin to stem cells seen in other organisms, and as such are responsible for new tissue growth. Many stem cells express kinases, a large family of enzymes that control many cellular processes. In this study we identified all the potential kinases in the liver fluke, including those that may function in neoblast-like stem cells. One of these kinases, polo-like kinase 1 (PLK1), has been linked to cancer development in humans. We used reverse genetics to silence this gene, allowing us to understand its function. Silencing PLK1 reduced worm growth and stopped neoblast-like cell proliferation, confirming that it has an important role in growth and cell division. Also, we showed that a PLK1 inhibitor, developed for cancer treatments, reduced growth and neoblast-like cell activity, illustrating the potential for targeting liver fluke kinases associated with neoblast-like cells with drugs, providing new routes to drug development. We then carried out RNA sequencing of worms after PLK1 was silenced to show the effects of neoblast-like cell loss on the expression of other genes. We found a decrease in the expression of genes that regulate cell division, but an increase in the expression of genes related to inter-cell signalling, including neuronal genes. This supports evidence for interactions between the nervous system and neoblast-like cells which could be exploited in future drug discovery.

molecular biology↗

bioRxiv2024

Wnt/β-catenin signalling underpins juvenile Fasciola hepatica growth and development

Infection by the liver fluke, Fasciola hepatica, places a substantial burden on the global agri-food industry and poses a significant threat to human health in endemic regions. Widespread resistance to a limited arsenal of chemotherapeutics, including the frontline flukicide triclabendazole (TCBZ), renders F. hepatica control unsustainable and accentuates the need for novel therapeutic target discovery. A key facet of F. hepatica biology is a population of specialised stem cells which drive growth and development - their dysregulation is hypothesised to represent an appealing avenue for control. The exploitation of this system as a therapeutic target is impeded by a lack of understanding of the molecular mechanisms underpinning F. hepatica growth and development. Wnt signalling pathways govern a myriad of stem cell processes during embryogenesis and drive tumorigenesis in adult tissues. Here, we identify five putative Wnt ligands and five Frizzled receptors in liver fluke transcriptomic datasets and find that Wnt/{beta}-catenin signalling is most active in juveniles, the most pathogenic life stage. FISH-mediated transcript localisation revealed partitioning of the five Wnt ligands, with each displaying a distinct expression pattern, consistent with each Wnt regulating the development of different cell/tissue types. The silencing of each individual Wnt or Frizzled gene yielded significant reductions in juvenile worm growth and, in select cases, blunted the proliferation of neoblast-like cells. Notably, silencing FhCTNNB1, the key effector of the Wnt/{beta}-catenin signal cascade led to aberrant development of the neuromuscular system which ultimately proved fatal - the first report of a lethal RNAi-induced phenotype in F. hepatica. The absence of any discernible phenotypes following the silencing of the inhibitory Wnt/{beta}-catenin destruction complex components is consistent with low destruction complex activity in rapidly developing juvenile worms, corroborates transcriptomic expression profiles and underscores the importance of Wnt signalling as a key molecular driver of growth and development in early stage juvenile fluke. The pharmacological inhibition of Wnt/{beta}-catenin signalling using commercially available inhibitors phenocopied RNAi results and provides impetus for drug repurposing. Taken together, these data functionally and chemically validate the targeting of Wnt signalling as a novel strategy to undermine the pathogenicity of juvenile F. hepatica. AUTHOR SUMMARYThe liver fluke, Fasciola hepatica significantly undermines the health and welfare of livestock worldwide and causes fascioliasis, a neglected tropical disease of humans. The most damaging stage of liver fluke infection is caused by the migration of juvenile worms within the liver tissue. Of all drugs approved for liver fluke treatment, just one, triclabendazole (TCBZ), is active on this pathogenic juvenile stage. TCBZ resistance is now widespread rendering liver fluke control unsustainable. This highlights the need for novel drug target identification and validation. A key aspect of juvenile worm biology is their ability to rapidly grow and develop, processes driven by a population of specialised stem cells. As such, the dysregulation of stem cells represents an attractive avenue for liver fluke control. One molecular pathway known to regulate stem cell dynamics in higher organisms is the Wnt signalling pathway. Bioinformatic searches of gene sequence datasets identified all major signalling components of both canonical and non-canonical Wnt pathways in F. hepatica. The localisation of FhWnt pathway components revealed remarkably distinct and widespread expression patterns throughout the F. hepatica body. Gene silencing of putative FhWnt pathway components revealed that those involved in the Wnt/{beta}-catenin signal cascade are fundamental to juvenile growth and, in some cases, stem-like cell proliferation. The silencing of liver fluke {beta}-catenin led to aberrant neuromuscular development and proved lethal to juvenile fluke. Biweekly exposures to commercially available Wnt pathway inhibitory compounds phenocopied the delayed development observed in the gene silencing experiments. These data suggest that FhWnt pathway components represent attractive targets for the development of novel flukicides or indeed, the repurposing of existing Wnt antagonists for parasite control.

developmental biology↗

bioRxiv2024

Exploitation of phylum-spanning omics resources reveals complexity in the nematode FLP signalling system and provides insights into flp-gene evolution

BackgroundParasitic nematodes significantly undermine global human and animal health and productivity. Parasite control is reliant on anthelmintic administration however over-use of a limited number of drugs has resulted in escalating parasitic nematode resistance, threatening the sustainability of parasite control and underscoring an urgent need for the development of novel therapeutics. FMRFamide-like peptides (FLPs), the largest family of nematode neuropeptides, modulate nematode behaviours including those important for parasite survival, highlighting FLP receptors (FLP-GPCRs) as appealing putative novel anthelmintic targets. Advances in omics resources have enabled the identification of FLPs and neuropeptide-GPCRs in some parasitic nematodes, but remaining gaps in FLP-ligand libraries hinder the characterisation of receptor-ligand interactions, which are required to drive the development of novel control approaches. ResultsIn this study we exploited recent expansions in nematode genome data to identify 2143 flp-genes in >100 nematode species across free-living, entomopathogenic, plant, animal and human lifestyles and representing 7 of the 12 major nematode clades (1). Our data reveal that: (i) the phylum-spanning flps, flp-1, -8, -14, and -18, may be representative of the flp profile of the last common ancestor of nematodes; (ii) the majority of parasitic nematodes have a reduced flp complement relative to free-living species; (iii) FLP prepropeptide architecture is variable within and between flp-genes and across nematode species; (iv) FLP prepropeptide signatures facilitate flp-gene discrimination; (v) FLP motifs display variable length, amino acid sequence, and conservation; (vi) CLANS analysis provides insight into the evolutionary history of flp-gene sequelogues and reveals putative flp-gene paralogues and, (viii) flp expression is upregulated in the infective larval stage of several nematode parasites. ConclusionsThese data provide the foundation required for phylum-spanning FLP-GPCR deorphanisation screens in nematodes to seed the discovery and development of novel parasite control approaches.

evolutionary biology↗

bioRxiv2023

Neoblast-like Stem Cells of Fasciola hepatica

The common liver fluke (Fasciola hepatica) causes the disease fasciolosis, which results in considerable losses within the global agri-food industry. There is a shortfall in the drugs that are effective against both the adult and juvenile life stages within the mammalian host, such that new drug targets are needed. Over the last decade the stem cells of parasitic flatworms have emerged as reservoirs of putative novel targets due to their role in development and homeostasis, including at host-parasite interfaces. Here, we investigate and characterise the proliferating cells that underpin development in F. hepatica. We provide evidence that these cells are capable of self-renewal, differentiation, and are sensitive to ionising radiation - all attributes of neoblasts in other flatworms. Changes in cell proliferation were also noted during the early stages of in vitro juvenile growth/development (around four to seven days post excystment), which coincided with a marked reduction in the nuclear area of proliferating cells. Furthermore, we generated transcriptomes from worms following irradiation-based ablation of neoblasts, identifying 124 significantly downregulated transcripts, including known stem cell markers such as fgfrA and plk1. Sixty-eight of these had homologues associated with neoblast-like cells in Schistosoma mansoni. Finally, RNA interference mediated knockdown of histone h2b (a marker of proliferating cells), ablated neoblast-like cells and impaired worm development in vitro. In summary, this work demonstrates that the proliferating cells of F. hepatica are equivalent to neoblasts of other flatworm species and demonstrate that they may serve as attractive targets for novel anthelmintics. Author SummaryLiver fluke are parasitic worms that infect both livestock and humans worldwide, threatening food security and human health. Treatments against this disease-causing parasite are limited, and growing resistance to drugs is undermining the effectiveness of control strategies. Since drugs represent the only viable control option, it is crucial that new drugs are discovered through the identification and validation of new drug targets. Stem cells play important roles in the normal growth and repair processes of many organisms, but when these cells become dysregulated through mutation, they can drive the development of cancers. Stem cells of liver fluke may be attractive novel drug targets as disruption would affect worm survival and/or development within their host. In this research we describe the characteristics of liver fluke stem cells, such as their sensitivity to radiation and their ability to develop into new cell types (key stem cell features). We used radiation in combination with RNA sequencing to identify genes associated with the liver fluke stem cells. Finally, we used reverse genetics to reduce the expression of a gene associated with stem cells, which led to the loss of stem cells and reduced worm growth/development. These data provide evidence to support the exploitation of stem cells as a source of novel drug targets for liver fluke control.

molecular biology↗

bioRxiv2021

Developmental regulation and functional prediction of microRNAs in an expanded Fasciola hepatica miRNome

1The liver fluke, Fasciola hepatica, is a global burden on the wellbeing and productivity of farmed ruminants, and a zoonotic threat to human health. Despite the clear need for accelerated discovery of new drug and vaccine treatments for this pathogen, we still have a relatively limited understanding of liver fluke biology and host interactions. Noncoding RNAs, including micro (mi)RNAs, are key to transcriptional regulation in all eukaryotes, such that an understanding of miRNA biology can shed light on organismal function at a systems level. Four previous publications have reported up to 89 mature miRNA sequences from F. hepatica, but our data show that this does not represent a full account of this species miRNome. We have expanded on previous studies by sequencing, for the first time, miRNAs from multiple life stages (adult, newly excysted juvenile (NEJ), metacercariae and adult-derived extracellular vesicles (EVs)). These experiments detected an additional 61 high-confidence miRNAs, most of which have not been described in any other species, expanding the F. hepatica miRNome to 150 mature sequences. We used quantitative (q)PCR assays to provide the first developmental profile of miRNA expression across metacercariae, NEJ, adult and adult-derived Evs. The majority of miRNAs were expressed most highly in metacercariae, with at least six distinct expression clusters apparent across life stages. Intracellular miRNAs were functionally analysed to identify target mRNAs with inversely correlated expression in F. hepatica tissue transcriptomes, highlighting regulatory interactions with key virulence transcripts including cathepsin proteases, and neuromuscular genes that control parasite growth, development and motility. We also linked 28 adult-derived EV miRNAs with downregulation of 397 host genes in F. hepatica-infected transcriptomes from ruminant lymph node, peripheral blood mononuclear cell (PBMC) and liver tissue transcriptomes. These included genes involved in signal transduction, immune and metabolic pathways, adding to the evidence for miRNA-based immunosuppression during fasciolosis. These data expand our understanding of the F. hepatica miRNome, provide the first data on developmental miRNA regulation in this species, and provide a set of testable hypotheses for functional genomics interrogations of liver fluke miRNA biology. CONTRIBUTION TO THE FIELDPrevious studies identified 89 micro (mi)RNAs (non-coding RNAs responsible for regulating gene expression) in the trematode parasite, Fasciola hepatica, and attached functional annotations to the miRNAs that are secreted by liver fluke in vitro. This study expands the known miRNA complement of F. hepatica by 40%, adding an additional 61 miRNAs, many of which appear Fasciola-specific. We used this expanded dataset to perform the first analysis of developmental miRNA expression across intra-mammalian parasites, showing clear developmentally regulated expression profiles across infectious metacercariae, juvenile and adult parasites, and extracellular vesicles secreted by adult parasites. We performed rigorous functional annotation of cellular miRNAs, correlating their expression with mRNA transcriptomes to identify potential roles for specific miRNAs in regulating expression of important proteases and nerve/muscle transcripts, all of which are important for parasite virulence. We also functionally analysed miRNAs secreted by adult parasites in terms of interactions with host transcripts; for the first time this analysis was supported by host transcriptome data, linking secreted miRNAs with mRNAs that are downregulated by fluke infection in sheep and cattle. This work contributes new data, insights and analyses to the field, providing a rich source of hypotheses for future experimental validation.

molecular biology↗

bioRxiv2021

In silico analyses of neuropeptide-like protein (NLP) profiles in parasitic nematodes

Nematode parasite infections cause disease in humans and animals and threaten global food security by reducing productivity in livestock and crop farming. The escalation of anthelmintic resistance in economically important nematode parasites underscores the need for the identification of novel drug targets in these worms. Nematode neuropeptide signalling is an attractive system for potential chemotherapeutic exploitation, with neuropeptide G-protein coupled receptors (NP-GPCRs) representing the leading target candidates therein. In order to successfully validate NP-GPCRs as targets for parasite control it is necessary to characterise their function and importance to nematode biology. This can be aided through identifying receptor activating ligand(s) in a process known as receptor deorphanisation. Such efforts first require the identification of all neuropeptide ligands within parasites. Here we comb the genomes of nine therapeutically relevant pathogenic nematode species to comprehensively characterise the nematode parasite neuropeptide-like protein (NLP) complements, and details the discovery of several previously unreported, yet conserved, neuropeptides and neuropeptide-encoding genes. We identify the neuropeptides that are most highly conserved in all parasites examined, and characterise their physiological activity on the reproductive musculature of the parasite, Ascaris suum. These data suggest conserved neuropeptide functions in both free living and parasitic nematodes, and support the potential for exploitation of the neuropeptide signalling system as an anthelmintic target.

neuroscience↗

bioRxiv2020

Extrasynaptic volume transmission: A novel route for neuropeptide signaling in nematodes

Neural circuit synaptic connectivities (the connectome) provide the anatomical foundation for our understanding of nematode nervous system function. However, other non-synaptic routes of communication are known in invertebrates including extrasynaptic volume transmission (EVT), which enables short- and/or long-range communication in the absence of synaptic connections. Although EVT has been highlighted as a facet of Caenorhabditis elegans neurosignaling, no experimental evidence identifies body cavity fluid (pseudocoelomic fluid; PCF) as a vehicle for either neuropeptide or biogenic amine transmission. In the parasitic nematode Ascaris suum FMRFamide-like peptides encoded on flp-18 potently stimulate female reproductive organs but are only expressed in cells that are anatomically distant from the reproductive organ, with no known synaptic connections to this tissue. Here we report a new non-synaptic mode of signaling in nematodes mediated by neuropeptides within the PCF. Our data show that: (i) A. suum PCF (As-PCF) contains a catalogue of neuropeptides including FMRFamide-like peptides and neuropeptide-like proteins; (ii) the A. suum FMRFamide-like peptide As-FLP-18A dominates the As-PCF peptidome; (iii) As-PCF potently modulates nematode reproductive muscle function ex vivo, mirroring the effects of synthetic FLP-18 peptides; (iv) As-PCF activates the C. elegans FLP-18 receptors NPR-4 and -5; (v) As-PCF alters C. elegans behavior and, (vi) FLP-18 and FLP-18 receptors display pan-phylum distribution in nematodes. Here we provide the first direct experimental evidence that supports an extrasynaptic volume route for neuropeptide transmission in nematodes. These data demonstrate non-synaptic signaling within the nematode functional connectome and are pertinent to receptor deorphanisation approaches underpinning drug discovery programs for nematode pathogens.

neuroscience↗

bioRxiv2020

RNA interference dynamics in juvenile Fasciola hepatica are altered during in vitro growth and development

For over a decade RNA interference (RNAi) has been an important molecular tool for functional genomics studies in parasitic flatworms. Despite this, our understanding of RNAi dynamics in many flatworm parasites, such as the temperate liver fluke (Fasciola hepatica), remains rudimentary. The ability to maintain developing juvenile fluke in vitro provides the opportunity to perform functional studies during development of the key pathogenic life stage. Here, we investigate the RNAi competence of developing juvenile liver fluke. Firstly, all life stages examined possess, and express, core candidate RNAi effectors encouraging the hypothesis that all life stages of F. hepatica are RNAi competent. RNAi effector analyses supported growing evidence that parasitic flatworms have evolved a separate clade of RNAi effectors with unknown function. Secondly, we assessed the impact of growth / development during in vitro culture on RNAi in F. hepatica juveniles and found that during the first week post-excystment liver fluke juveniles exhibit quantitatively lower RNAi mediated transcript knockdown when maintained in growth inducing media. This did not appear to occur in older in vitro juveniles, suggesting that rapidly shifting transcript dynamics over the first week following excystment alters RNAi efficacy after a single 24 hour exposure to double stranded (ds)RNA. Finally, RNAi efficiency was found to be improved through use of a repeated dsRNA exposure methodology that has facilitated silencing of genes in a range of tissues, thereby increasing the utility of RNAi as a functional genomics tool in F. hepatica.

molecular biology↗

bioRxiv2017

Profiling G protein-coupled receptors of Fasciola hepatica identifies orphan rhodopsins unique to phylum Platyhelminthes

G protein-coupled receptors (GPCRs) are established drug targets. Despite their considerable appeal as targets for next-generation anthelmintics, poor understanding of their diversity and function in parasitic helminths has thwarted progress towards GPCR-targeted anti-parasite drugs. This study facilitates GPCR research in the liver fluke, Fasciola hepatica, by generating the first profile of GPCRs from the F. hepatica genome. Our dataset describes 146 high confidence GPCRs, representing the largest cohort of GPCRs, and the most complete set of in silico ligand-receptor predictions, yet reported in any parasitic helminth. All GPCRs fall within the established GRAFS nomenclature; comprising three glutamate, 135 rhodopsin, two adhesion, five frizzled and one smoothened GPCR. Stringent annotation pipelines identified 18 highly diverged rhodopsins in F. hepatica that maintained core rhodopsin signatures, but lacked significant similarity with non-flatworm sequences, providing a new sub-group of potential flukicide targets. These facilitated identification of a larger cohort of 76 related sequences from available flatworm genomes, representing new members of existing groups of flatworm-specific rhodopsins. These receptors imply flatworm specific GPCR functions, and/or co-evolution with unique flatworm ligands, and could facilitate development of exquisitely selective anthelminthics. Ligand binding domain sequence conservation relative to deorphanised rhodopsins enabled high confidence ligand-receptor matching of seventeen receptors activated by acetylcholine, neuropeptide F/Y, octopamine or serotonin. RNA-Seq analyses showed expression of 101 GPCRs across various developmental stages, with the majority expressed most highly in the pathogenic intra-mammalian juvenile parasites. These data identify a broad complement of GPCRs in F. hepatica, including rhodopsins likely to have key functions in neuromuscular control and sensory perception, as well as frizzled and adhesion families implicated, in other species, in growth, development and reproduction. This catalogue of liver fluke GPCRs provides a platform for new avenues into our understanding of flatworm biology and anthelmintic discovery.\n\nAuthor SummaryFasciola spp. liver fluke are important veterinary pathogens with impacts on human and animal health, and food security, around the world. Liver fluke have developed resistance to most of the drugs used to treat them (flukicides). Since no vaccines exist, we need to develop new flukicides as a matter of urgency. Most anthelmintic drugs used to treat parasitic worm infections operate by impeding the functioning of their nerve and muscle. In flatworms, most nervous signals are received by a type of receptor called a G protein-coupled receptor (GPCR). Since GPCRs control important parasite functions (e.g. movement, egg-laying, feeding), they represent appealing targets for new flukicides, but have not yet been targeted as such. This work exploited the F. hepatica genome to determine the quantity and diversity of GPCRs in liver fluke. We found more GPCRs in the Fasciola genome than have been reported in any other parasitic worm. These findings provide a foundation that for researchers to determine the functions of these receptors, and which molecules/ligands they are activated by. These data will pave the way to exploring the potential of F. hepatica GPCRs as targets for new flukicides.

bioinformatics↗