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Confirmation of ivermectin resistance genes identified by whole genome sequencing by testing on 10 nM ivermectin plates. Wild type N2 were killed and failed to progress beyond L1 (A), compared with TP238 which survive to adult stage on 10 nM IVM (B). TP238(ka32) mapping candidate alleles CB1124(che-3, e1124) (C) CB1253 (che-3, e1253) (D) also survive to adult stage on 10 nM IVM plates. A-D, 20 embryos added per plate and left or 3 days, (magnification Â80). RNA interference (RNAi) testing of candidate genes for resistance to 10 nM ivermectin. E-H (Â40). Empty vector RNAi control (L4440) treated N2 killed on 10 nM ivermectin (E) compared with resistant strain TP239(ka33) (F) which progresses to adulthood. TP238(ka32) mapping candidate che-3 (F18C12.1 RNAi) fed to N2 strain (G) and TP239(ka33) mapping candidate dhc-3 (B0365.7 RNAi) fed to N2 strain (H); both survived to adulthood on 10 nM ivermectin.
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Parasitic nematodes represent formidable pathogens of humans, livestock and crop plants. Control of these parasites is almost exclusively dependent on a small group of anthelmintic drugs, the most important of which belong to the macrocyclic lactone class. The extensive use of these drugs to control the ubiquitous trichostrongylid parasites of graz...
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... mapping candidates were examined further by obtaining two of the available mutant alleles of che-3 and by applying an RNAi approach to determine if knockdown of both candidate genes would confer IVM resistance in the aforementioned IVM plate assays (Fig. 2). Pre-existing mutants were only available for che-3 but not dhc-3 (www.wormbase.org), and two independent che-3 alleles (e1124 and e1253) were tested and found to survive to adulthood on 10 nM IVM plates (Fig. 2C and D), being comparable to the TP238(ka32) mutant strain (Fig. 2B) and in marked contrast to the wild type strain N2, which ...
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... an RNAi approach to determine if knockdown of both candidate genes would confer IVM resistance in the aforementioned IVM plate assays (Fig. 2). Pre-existing mutants were only available for che-3 but not dhc-3 (www.wormbase.org), and two independent che-3 alleles (e1124 and e1253) were tested and found to survive to adulthood on 10 nM IVM plates (Fig. 2C and D), being comparable to the TP238(ka32) mutant strain (Fig. 2B) and in marked contrast to the wild type strain N2, which arrests at L1 under identical selection conditions (Fig. 2A). The mapping data was also supported for both che-3 and dhc-3 following and RNAi approach whereby resistance to 10 nM IVM was conferred to the normally ...
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... would confer IVM resistance in the aforementioned IVM plate assays (Fig. 2). Pre-existing mutants were only available for che-3 but not dhc-3 (www.wormbase.org), and two independent che-3 alleles (e1124 and e1253) were tested and found to survive to adulthood on 10 nM IVM plates (Fig. 2C and D), being comparable to the TP238(ka32) mutant strain (Fig. 2B) and in marked contrast to the wild type strain N2, which arrests at L1 under identical selection conditions (Fig. 2A). The mapping data was also supported for both che-3 and dhc-3 following and RNAi approach whereby resistance to 10 nM IVM was conferred to the normally susceptible N2 strain, by pre-exposing this strain to ...
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... for che-3 but not dhc-3 (www.wormbase.org), and two independent che-3 alleles (e1124 and e1253) were tested and found to survive to adulthood on 10 nM IVM plates (Fig. 2C and D), being comparable to the TP238(ka32) mutant strain (Fig. 2B) and in marked contrast to the wild type strain N2, which arrests at L1 under identical selection conditions (Fig. 2A). The mapping data was also supported for both che-3 and dhc-3 following and RNAi approach whereby resistance to 10 nM IVM was conferred to the normally susceptible N2 strain, by pre-exposing this strain to corresponding RNAi feeding constructs prior to exposure to 10 nM IVM. The RNAi empty feeding vector control did not permit survival ...
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... mapping data was also supported for both che-3 and dhc-3 following and RNAi approach whereby resistance to 10 nM IVM was conferred to the normally susceptible N2 strain, by pre-exposing this strain to corresponding RNAi feeding constructs prior to exposure to 10 nM IVM. The RNAi empty feeding vector control did not permit survival on 10 nM IVM (Fig. 2E) in contrast to the TP238(ka32) (Fig. 2B) and TP239(ka33) (Fig. 2F) mutant strains which survived this treatment. Similarly, the TP238(ka32) candidate che-3 (F18c12.1) (Fig. 2G) and the TP239(ka33) candidate dhc-3 (B0365.7) RNAi feeding (Fig. 2H) of the N2 strain both permitted survival and allowed development to adulthood on the ...
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... che-3 and dhc-3 following and RNAi approach whereby resistance to 10 nM IVM was conferred to the normally susceptible N2 strain, by pre-exposing this strain to corresponding RNAi feeding constructs prior to exposure to 10 nM IVM. The RNAi empty feeding vector control did not permit survival on 10 nM IVM (Fig. 2E) in contrast to the TP238(ka32) (Fig. 2B) and TP239(ka33) (Fig. 2F) mutant strains which survived this treatment. Similarly, the TP238(ka32) candidate che-3 (F18c12.1) (Fig. 2G) and the TP239(ka33) candidate dhc-3 (B0365.7) RNAi feeding (Fig. 2H) of the N2 strain both permitted survival and allowed development to adulthood on the normally lethal 10 nM IVM ...
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... and RNAi approach whereby resistance to 10 nM IVM was conferred to the normally susceptible N2 strain, by pre-exposing this strain to corresponding RNAi feeding constructs prior to exposure to 10 nM IVM. The RNAi empty feeding vector control did not permit survival on 10 nM IVM (Fig. 2E) in contrast to the TP238(ka32) (Fig. 2B) and TP239(ka33) (Fig. 2F) mutant strains which survived this treatment. Similarly, the TP238(ka32) candidate che-3 (F18c12.1) (Fig. 2G) and the TP239(ka33) candidate dhc-3 (B0365.7) RNAi feeding (Fig. 2H) of the N2 strain both permitted survival and allowed development to adulthood on the normally lethal 10 nM IVM ...
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... this strain to corresponding RNAi feeding constructs prior to exposure to 10 nM IVM. The RNAi empty feeding vector control did not permit survival on 10 nM IVM (Fig. 2E) in contrast to the TP238(ka32) (Fig. 2B) and TP239(ka33) (Fig. 2F) mutant strains which survived this treatment. Similarly, the TP238(ka32) candidate che-3 (F18c12.1) (Fig. 2G) and the TP239(ka33) candidate dhc-3 (B0365.7) RNAi feeding (Fig. 2H) of the N2 strain both permitted survival and allowed development to adulthood on the normally lethal 10 nM IVM ...
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... to exposure to 10 nM IVM. The RNAi empty feeding vector control did not permit survival on 10 nM IVM (Fig. 2E) in contrast to the TP238(ka32) (Fig. 2B) and TP239(ka33) (Fig. 2F) mutant strains which survived this treatment. Similarly, the TP238(ka32) candidate che-3 (F18c12.1) (Fig. 2G) and the TP239(ka33) candidate dhc-3 (B0365.7) RNAi feeding (Fig. 2H) of the N2 strain both permitted survival and allowed development to adulthood on the normally lethal 10 nM IVM ...
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... plates. An example of a novel, strong IVM-resistant chemosensory defective strain che-11(e1810) (Fig. 1D) and its ability to exclude Dil from the amphids (Fig. 1H) is presented. This linkage of IVM resistance to Dil exclusion is also shown for a representative osmotic avoidance mutant osm-1(p808) (Fig. 1I), and a dye-filling mutant dyf-7(m537) (Fig. 2J), both of which are resistant to IVM (Table 2). In total, 31 mutant strains from six different gene classes were tested and only one, che-6(e1126), was found to be sensitive to 10 nM IVM. All 31 genes have been described as being dye-filling defective (Starich et al., 1995), but only four (che-3, osm-1, osm-5 and dyf-11) had previously ...
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Due to widespread multi-drug resistance in parasitic nematodes of livestock animals, there is an urgent need to discover new anthelmintics with distinct mechanisms of action. Extending previous work, here we screened a panel of 245 chemically-diverse small molecules for anti-parasitic activity against Haemonchus contortus—an economically important...
Citations
... Combinatorial treatments also present new considerations as it relates to multidrug resistance, which complicates the treatment of malaria [14] and a growing number of helminths [15,16]. While there are active efforts to better understand mechanisms of anthelmintic resistance in human and animal populations [17][18][19][20][21][22], it is unclear how resistance mechanisms that alter susceptibility to one drug affect the interactions and efficacy of drugs used in combination. ...
... Validated resistance mechanisms in parasitic nematodes are restricted to mutations in the cytoskeletal targets of the benzimidazoles [5], but genetic tools in the model nematode Caenorhabditis elegans have helped to identify anthelmintic resistance mechanisms beyond drug target mutations [23]. These include mutations that affect the ability of drugs to accumulate within the worm by altering drug uptake, distribution, efflux, or metabolism [17,19,24,25]. Genetic mapping [21,26,27] and phenotypic observations [19,28] of anthelmintic responses in parasitic nematodes suggest that these resistance mechanisms are field relevant. ...
... Anthelmintics can be absorbed by nematodes via crossing the cuticle, diffusing through the cilia of the amphid neurons, or being ingested through the pharynx and intestine [29]. Mutations that alter these putative drug interfaces can selectively modulate anthelmintic activity in model nematodes [17,18,25,[30][31][32][33][34][35]. We set out to investigate how genetic perturbations that impact drug entry and resistance to a given anthelmintic can alter the landscape of interactions between anthelmintics belonging to different classes. ...
Parasitic nematodes infect billions of people and are mainly controlled by anthelmintic mass drug administration (MDA). While there are growing efforts to better understand mechanisms of anthelmintic resistance in human and animal populations, it is unclear how resistance mechanisms that alter susceptibility to one drug affect the interactions and efficacy of drugs used in combination. Mutations that alter drug permeability across primary nematode barriers have been identified as potential resistance mechanisms using the model nematode Caenorhabditis elegans . We leveraged high-throughput assays in this model system to measure altered anthelmintic susceptibility in response to genetic perturbations of potential cuticular, amphidial, and alimentary routes of drug entry. Mutations in genes associated with these tissue barriers differentially altered susceptibility to the major anthelmintic classes (macrocyclic lactones, benzimidazoles, and nicotinic acetylcholine receptor agonists) as measured by animal development. We investigated two-way anthelmintic interactions across C . elegans genetic backgrounds that confer resistance or hypersensitivity to one or more drugs. We observe that genetic perturbations that alter susceptibility to a single drug can shift the drug interaction landscape and lead to the appearance of novel synergistic and antagonistic interactions. This work establishes a framework for investigating combinatorial therapies in model nematodes that can potentially be translated to amenable parasite species.
... In the veterinary realm, combination anthelmintics are used to expand the spectrum of antiparasitic activity and to help delay or overcome single-drug resistance [11][12][13]. While there are active efforts to better understand mechanisms of anthelmintic resistance in human and animal populations [14][15][16][17][18][19], it is unclear how resistance mechanisms that alter susceptibility to one drug affect the interactions and efficacy of drugs used in combination. ...
... Validated resistance mechanisms in parasitic nematodes are restricted to mutations in the cytoskeletal targets of the benzimidazoles [5], but genetic tools in the model nematode Caenorhabditis elegans have helped to identify anthelmintic resistance mechanisms beyond drug target mutations [20]. These include mutations that affect the ability of drugs to accumulate within the worm by altering drug uptake, distribution, efflux, or metabolism [14,16,21,22]. Genetic mapping [18,23,24] and phenotypic observations [16,25] of anthelmintic responses in parasitic nematodes suggest that these resistance mechanisms are field relevant. ...
... Anthelmintics can be absorbed by nematodes via crossing the cuticle, diffusing through the cilia of the amphid neurons, or being ingested through the pharynx and intestine [26]. Mutations that alter these putative drug interfaces can selectively modulate anthelmintic activity in model nematodes [14,15,22,[27][28][29][30][31][32]. We set out to investigate how genetic perturbations that impact drug entry and resistance to a given anthelmintic can alter the landscape of interactions between anthelmintics belonging to different classes. ...
Parasitic nematodes infect billions of people and are mainly controlled by anthelmintic mass drug administration (MDA). While there are growing efforts to better understand mechanisms of anthelmintic resistance in human and animal populations, it is unclear how resistance mechanisms that alter susceptibility to one drug affect the interactions and efficacy of drugs used in combination. Mutations that alter drug permeability across primary nematode barriers have been identified as potential resistance mechanisms using the model nematode Caenorhabditis elegans . We leveraged high-throughput assays in this model system to measure altered anthelmintic susceptibility in response to genetic perturbations of potential cuticular, amphidial, and alimentary routes of drug entry. Mutations in genes associated with these tissue barriers differentially altered susceptibility to the major anthelmintic classes (macrocyclic lactones, benzimidazoles, and nicotinic acetylcholine receptor agonists) as measured by animal development. We investigated two-way anthelmintic interactions across C. elegans genetic backgrounds that confer resistance or hypersensitivity to one or more drugs. We observe that genetic perturbations that alter susceptibility to a single drug can shift the drug interaction landscape and lead to the appearance of novel synergistic and antagonistic interactions. This work establishes a framework for investigating combinatorial therapies in model nematodes that can potentially be translated to amenable parasite species.
... The MLs comprise avermectins and milbemycins and are an essential class of anthelmintics because of our high dependence on them to control nematode parasites in livestock, companion animals, and humans [36]. Previous genetic screens performed in the C. elegans laboratory-adapted reference strain, N2, identified three genes that encode glutamate-gated chloride (GluCl) channel subunits (glc-1, avr-14, and avr-15) that are targeted by MLs [37,38]. Studies of abamectin have found additional loci involved in resistance [18]. ...
Treatment of parasitic nematode infections in humans and livestock relies on a limited arsenal of anthelmintic drugs that have historically reduced parasite burdens. However, anthelmintic resistance (AR) is increasing, and little is known about the molecular and genetic causes of resistance for most drugs. The free-living roundworm Caenorhabditis elegans has proven to be a tractable model to understand AR, where studies have led to the identification of molecular targets of all major anthelmintic drug classes. Here, we used genetically diverse C. elegans strains to perform dose-response analyses across 26 anthelmintic drugs that represent the three major anthelmintic drug classes (benzimidazoles, macrocyclic lactones, and nicotinic acetylcholine receptor agonists) in addition to seven other anthelmintic classes. First, we found that C. elegans strains displayed similar anthelmintic responses within drug classes and significant variation across drug classes. Next, we compared the effective concentration estimates to induce a 10% maximal response (EC10) and slope estimates of each dose-response curve of each strain to the laboratory reference strain, which enabled the identification of anthelmintics with population-wide differences to understand how genetics contribute to AR. Because genetically diverse strains displayed differential susceptibilities within and across anthelmintics, we show that C. elegans is a useful model for screening potential nematicides before applications to helminths. Third, we quantified the levels of anthelmintic response variation caused by genetic differences among individuals (heritability) to each drug and observed a significant correlation between exposure closest to the EC10 and the exposure that exhibited the most heritable responses. These results suggest drugs to prioritize in genome-wide association studies, which will enable the identification of AR genes.
... In the context of natural parasitic nematode populations, it is easy 262 to imagine how such beneficial alleles could spread rapidly and further exacerbate parasitic The MLs comprise avermectins and milbemycins and are an essential class of 268 anthelmintics because of our high dependence on them to control nematode parasites in 269 livestock, companion animals, and humans [37]. Previous genetic screens performed in the 270 C. elegans laboratory-adapted reference strain, N2, identified three genes that encode glutamate-271 gated chloride (GluCl) channel subunits (glc-1, avr-14, and avr-15) that are targeted by MLs 272 [38,39]. Studies of abamectin have found additional loci involved in resistance [36]. ...
Treatment of parasitic nematode infections in humans and livestock relies on a small arsenal of anthelmintic drugs that have historically reduced parasite burdens. However, anthelmintic resistance (AR) is increasing, and little is known about the molecular and genetic causes of resistance for most drugs. The free-living roundworm Caenorhabditis elegans has proven to be a tractable model to understand AR, where studies have led to the identification of molecular targets of all major anthelmintic drug classes. Here, we used genetically diverse C. elegans strains to perform dose-response analyses across 26 anthelmintic drugs that represent the three major anthelmintic drug classes (benzimidazoles, macrocyclic lactones, and nicotinic acetylcholine receptor agonists) in addition to seven other anthelmintic classes. First, we found that C. elegans strains displayed significant variation in anthelmintic responses across drug classes. Dose-response trends within a drug class showed that the C. elegans strains elicited similar responses within the benzimidazoles but variable responses in the macrocyclic lactones and nicotinic acetylcholine receptor agonists. Next, we compared the effective concentration estimates to induce a 10% maximal response (EC 10 ) and slope estimates of each dose-response curve of each strain to the reference strain, N2, which enabled the identification of anthelmintics with population-wide differences to understand how genetics contribute to AR. Because genetically diverse strains displayed differential susceptibilities within and across anthelmintics, we show that C. elegans is a useful model for screening potential nematicides. Third, we quantified the heritability of responses to each anthelmintic and observed a significant correlation between exposure closest to the EC 10 and the exposure that exhibited the most heritable responses. Heritable genetic variation can be explained by strain-specific anthelmintic responses within and across drug classes. These results suggest drugs to prioritize in genome-wide association studies, which will enable the identification of AR genes.
AUTHOR SUMMARY
Parasitic nematodes infect most animal species and significantly impact human and animal health. Control of parasitic nematodes in host species relies on a limited collection of anthelmintic drugs. However, anthelmintic resistance is widespread, which threatens our ability to control parasitic nematode populations. Here, we used the non-parasitic roundworm Caenorhabditis elegans as a model to study anthelmintic resistance across 26 anthelmintics that span ten drug classes. We leveraged the genetic diversity of C. elegans to quantify anthelmintic responses across a range of doses, estimate dose-response curves, fit strain-specific model parameters, and calculate the contributions of genetics to these parameters. We found that genetic variation within a species plays a considerable role in anthelmintic responses within and across drug classes. Our results emphasize how the incorporation of genetically diverse C. elegans strains is necessary to understand anthelmintic response variation found in natural populations. These results highlight drugs to prioritize in future mapping studies to identify genes involved in anthelmintic resistance.
GRAPHICAL ABSTRACT
... Although the main chromosome 5 QTL at 37.5 Mb was present in all selection experiments with ivermectin, the secondary QTLs were variable between replicates and experiments. The chromosome 2 QTL (region: 2,992,500-3,267,500; most prominent in Figure S1 X-QTL replicate 1) contained two previously described candidate genes, osm-1 (HCON_00035760) and che-11 (HCON_00035880), that have been shown to confer resistance either directly (Page, 2018) or additively with other variants (Dent et al., 2000) in C. elegans. Neither gene contained high effect variants; however, both contained a number of nonsynonymous variants, including three moderately differentiated variants between pre-and post-treatment in osm-1 (pos. ...
Like other pathogens, parasitic helminths can rapidly evolve resistance to drug treatment. Understanding the genetic basis of anthelmintic drug resistance in parasitic nematodes is key to tracking its spread and improving the efficacy and sustainability of parasite control. Here, we use an in vivo genetic cross between drug-susceptible and multi-drug-resistant strains of Haemonchus contortus in a natural host-parasite system to simultaneously map resistance loci for the three major classes of anthelmintics. This approach identifies new alleles for resistance to benzimidazoles and levamisole and implicates the transcription factor cky-1 in ivermectin resistance. This gene is within a locus under selection in ivermectin-resistant populations worldwide; expression analyses and functional validation using knockdown experiments support that cky-1 is associated with ivermectin survival. Our work demonstrates the feasibility of high-resolution forward genetics in a parasitic nematode and identifies variants for the development of molecular diagnostics to combat drug resistance in the field.
... However, widespread resistance to MLs has been reported and is a significant concern [10]. Genetic screens and selections performed in the laboratory-adapted reference strain of the free-living nematode Caenorhabditis elegans have identified three genes (glc-1, avr-14, and avr-15) that are targeted by MLs in C. elegans and encode glutamate-gated chloride (GluCl) channel subunits [12,13]. Several additional genes (glc-2, glc-3, and glc-4) that form subunits of GluCl channels exist and might be relevant to ML resistance [14]. ...
Parasitic nematodes cause a massive worldwide burden on human health along with a loss of livestock and agriculture productivity. Anthelmintics have been widely successful in treating parasitic nematodes. However, resistance is increasing, and little is known about the molecular and genetic causes of resistance for most of these drugs. The free-living roundworm Caenorhabditis elegans provides a tractable model to identify genes that underlie resistance. Unlike parasitic nematodes, C . elegans is easy to maintain in the laboratory, has a complete and well annotated genome, and has many genetic tools. Using a combination of wild isolates and a panel of recombinant inbred lines constructed from crosses of two genetically and phenotypically divergent strains, we identified three genomic regions on chromosome V that underlie natural differences in response to the macrocyclic lactone (ML) abamectin. One locus was identified previously and encodes an alpha subunit of a glutamate-gated chloride channel ( glc-1 ). Here, we validate and narrow two novel loci using near-isogenic lines. Additionally, we generate a list of prioritized candidate genes identified in C . elegans and in the parasite Haemonchus contortus by comparison of ML resistance loci. These genes could represent previously unidentified resistance genes shared across nematode species and should be evaluated in the future. Our work highlights the advantages of using C . elegans as a model to better understand ML resistance in parasitic nematodes.
... | Drug screening assaysDrug ingestion is probably the main way through which xenobiotic molecules can gain access to target tissues in wild-type C. elegans.132,133 However, the amphids, a pair of anterior sensory structures opened to the outside environment, and the vulva are also involved in drug and nanoparticles intake, respectively.134,135 Moreover, the use of animals that have a compromised cuticle can significantly increase drug absorption.97 ...
Therapeutic drug development is a long, expensive, and complex process that usually takes 12-15 years. In the early phases of drug discovery, in particular, there is a growing need for animal models that ensure the reduction in both cost and time. Caenorhabditis elegans has been traditionally used to address fundamental aspects of key biological processes, such as apoptosis, aging, and gene expression regulation. During the last decade, with the advent of large-scale platforms for screenings, this invertebrate has also emerged as an essential tool in the pharmaceutical research industry to identify novel drugs and drug targets. In this review, we discuss the reasons why C. elegans has been positioned as an outstanding cost-effective option for drug discovery, highlighting both the advantages and drawbacks of this model. Particular attention is paid to the suitability of this nematode in large-scale genetic and pharmacological screenings. High-throughput screenings in C. elegans have indeed contributed to the breakthrough of a wide variety of candidate compounds involved in extensive fields including neurodegeneration, pathogen infections and metabolic disorders. The versatility of this nematode, which enables its instrumentation as a model of human diseases, is another attribute also herein underscored. As illustrative examples, we discuss the utility of C. elegans models of both human neurodegenerative diseases and parasitic nematodes in the drug discovery industry. Summing up, this review aims to demonstrate the impact of C. elegans models on the drug discovery pipeline.
... Interestingly, in C. elegans, an additional dynein heavy chain, i.e. DHC-3, has been implicated in the formation of a subset of cilia, and DHC-3 was identifiedtogether with the dynein-2 heavy chainin genetic screens for anti-helminth resistance (Page, 2018). The deposited protein sequence for DHC-3 suggests it to be a highly divergent dynein heavy chain that lacks ATP-binding sites is, thus, unlikely to function as a conventional motor. ...
Cytoplasmic dynein-2 is a motor protein complex that drives the movement of cargoes along microtubules within cilia, facilitating the assembly of these organelles on the surface of nearly all mammalian cells. Dynein-2 is crucial for ciliary function, as evidenced by deleterious mutations in patients with skeletal abnormalities. Long-standing questions include how the dynein-2 complex is assembled, regulated, and switched between active and inactive states. A combination of model organisms, in vitro cell biology, live-cell imaging, structural biology and biochemistry has advanced our understanding of the dynein-2 motor. In this Cell Science at a Glance article and the accompanying poster, we discuss the current understanding of dynein-2 and its roles in ciliary assembly and function.
... First, unbiased screens for drug resistance have independently 88 identified the Dyf phenotype as a common feature in drug resistant C. elegans (Fujii et 89 al., 2004, Menez et al., 2016, Collins et al., 2008. Selection for resistance to the 90 anthelmintic drug ivermectin was shown to enrich for Dyf mutants in several forward 91 genetic screens (Menez et al., 2016, Page, 2018, Dent et al., 2000. Follow up work 92 identified P-glycoproteins, a class of ATP binding cassette (ABC) transporters, as the 93 drivers behind ivermectin resistance in Dyf mutants (Ardelli and Prichard, 2013). ...
Longevity is often associated with stress resistance, but whether they are causally linked is incompletely understood. Here we investigate chemosensory defective Caenorhabditis elegans mutants that are long-lived and stress resistant. We find that mutants in the intraflagellar transport protein gene osm-3 are completely protected from tunicamycin (TM)-induced ER stress. While osm-3 lifespan extension is fully dependent on the key longevity factor DAF-16/FOXO, TM resistance is not. osm-3 mutants are protected from bacterial pathogens, which is fully pmk-1 p38 MAP kinase dependent. Transcriptomic analysis revealed enhanced expression of P-glycoprotein xenobiotic detoxification genes in osm-3 mutants and chemical inhibition of P-glycoproteins with verapamil suppressed TM resistance. Of note, the nuclear hormone receptor nhr-8 is necessary and sufficient to regulate P-glycoproteins and TM resistance. We thus identify a cell-nonautonomous regulation of xenobiotic detoxification and show that separate pathways are engaged to mediate longevity, pathogen resistance, and xenobiotic detoxification in osm-3 mutants.
... It is not known at this early stage whether the new compounds share the mode of action of the closed macrocycles and whether they possess pharmacological advantages or disadvantages. It would be especially interesting to learn whether they also utilise the unexpected route of entry into nematodes recently described for ivermectin [104]. ...
Here, the scientific and patent literature on the activities of purified natural compounds has been reviewed, with the aim of assessing their suitability as anthelmintic drug discovery starting points. Only compounds described as active against parasitic nematodes of animals or against the model nematode Caenorhabditis elegans have been analysed. Scientific articles published since 2010 and patents granted from 2000, both inclusive, have been included in this analysis. The results show a scarcity of novel chemical structures, a limited follow-up of compounds disclosed before 2010 and a bias towards the screening of plant products, almost to the exclusion of other sources, when microbial extracts have, historically, provided most starting points for anti-infective drugs. All plant products published in this period were previously known, alerting to the high re-discovery rates of a limited number of chemical classes from this source. The most promising compounds described in the literature reviewed here, namely the linear nemadectin-derivatives, are novel and of bacterial origin. Patented but otherwise unpublished spiroketal structures also appear as interesting scaffolds for future development. The patent literature confirmed that it is possible to patent derivatives of previously known products, making them valid starting points for translational research.
