Egg-laying and locomotory screens with C. elegans yield a nematode-selective small molecule stimulator of neurotransmitter release

Line-scan imaging for real-time phenotypic screening of C. elegans

Phenotypic screens of living organisms often require real-time, high spatial resolution imaging. We report here on the design and application of a line-scan imaging platform that enables bright-field imaging of live nematodes using a 96-well plate configuration. The system optics are such that each individual well is projected across the full field of view of a 4 K line scanning camera. To minimize motional artifacts, the camera system is translated, while the sample is kept stationary. We discuss the challenges in establishing flat field illumination, image registration and stitching, and the opportunities that this platform has enabled for phenotypic screens of living systems.

Antiaging Effect of 2-O-β-D-Glucopyranosyl Ascorbic Acid Derived from Lycium barbarum L. Through Modulating the IIS Pathway and Gut Microbiota in Caenorhabditis elegans

2-O-β-D-Glucopyranosyl ascorbic acid (AA-2βG), a bioactive ascorbic acid derivative isolated from the fruits of Lycium barbarum L., exhibited significant antiaging effects in Caenorhabditis elegans. It significantly extended their lifespan, enhanced stress resistance, reduced lipofuscin accumulation, and improved their healthspan, while strengthening antioxidant defenses. Transcriptomic analysis identified the insulin/insulin-like growth factor (IGF)-1 signaling pathway as a key regulator, with quantitative real-time polymerase chain reaction confirming the upregulation of longevity-associated genes. Functional studies showed that the transcription factors DAF-16, HSF-1, and SIR-2.1 were essential for the lifespan-extending effects of AA-2βG, as mutations in these genes abolished lifespan extension. Moreover, 16S rRNA sequencing revealed that AA-2βG modulated gut microbiota by increasing longevity-associated taxa and reducing pro-aging species, with these alterations linked to metabolic pathways. These findings suggest that AA-2βG exerts antiaging effects through the coordinated regulation of the IIS pathway and gut microbiota composition, highlighting its potential as a natural geroprotective compound.

Advances in Anthelmintic Target Identification

Parasitic nematodes pose a significant threat to human and animal health, causing widespread morbidity and substantial socioeconomic losses globally. Despite the utility of anthelmintic drugs in parasite control, the emergence of widespread resistance necessitates the discovery of novel interventions. Advances through the use of whole-organism phenotypic screening have identified some promising nematocidal compounds, including nemacol, tolfenpyrad, UMW-9729, and ABX464. This article summarises efforts in this discovery, with a focus on Haemonchus contortus and Caenorhabditis elegans as model nematodes, and discusses approaches used for drug target deconvolution, including proteomic, chemical and genetic/genomic techniques. Stability-based proteomic assays, such as thermal proteome profiling, have been useful for identifying protein targets for these compounds, shedding light on their mechanisms of action. However, challenges remain in extrapolating findings from C. elegans to parasitic nematodes, emphasising the need for validation studies. Understanding drug-target interactions in nematodes is critical for developing next-generation anthelmintics and for mitigating the growing resistance challenge. This review outlines recent progress in this area and discusses future directions in target validation and anthelmintic development to support parasite control programmes.

Sensory modulation of neuropeptide signaling by CASY-1 gates cholinergic transmission at Caenorhabditis elegans neuromuscular junction

The neuromuscular junction (NMJ) is crucial for understanding the fundamentals of synaptic transmission and activity. Various modulators operate within neuronal circuits, from sensory to motor neurons, to influence synaptic transmission at the NMJ. This study sheds light on the regulation of sensory-evoked cholinergic neurotransmission at motor neurons orchestrated by CASY-1, the mammalian calsyntenin orthologue. We report that the increased excitation-inhibition (E-I) ratio at the NMJ in casy-1 mutants is likely due to its interactions with neuromodulators in sensory neurons. We explored the intricate genetic interactions of CASY- 1 with the neuropeptide FLP-21 and its receptor, NPR-1, both of which display simultaneous alterations in cholinergic signaling at the NMJ. Through genetic, pharmacological, and bioimaging-based experiments, we proposed a mechanism by which CASY-1 potentially interacts with the neuropeptide-carrying vesicles to regulate synaptic transmission. The nematode Caenorhabditis elegans serves as an ideal model system for this study, enabling detailed insights into neuromodulatory mechanisms in the neuronal circuit.

Automated multimodal imaging of Caenorhabditis elegans behavior in multi-well plates

Assays of behavior in model organisms play an important role in genetic screens, drug testing, and the elucidation of gene-behavior relationships. We have developed an automated, high-throughput imaging and analysis method for assaying behaviors of the nematode C. elegans. We use high-resolution optical imaging to longitudinally record the behaviors of 96 animals at a time in multi-well plates, and computer vision software to quantify the animals' locomotor activity, behavioral states, and egg laying events. To demonstrate the capabilities of our system we used it to examine the role of serotonin in C. elegans behavior. We found that egg-laying events are preceded by a period of reduced locomotion, and that this decline in movement requires serotonin signaling. In addition, we identified novel roles of serotonin receptors SER-1 and SER-7 in regulating the effects of serotonin on egg laying across roaming, dwelling, and quiescent locomotor states. Our system will be useful for performing genetic or chemical screens for modulators of behavior.

Automated multimodal imaging of Caenorhabditis elegans behavior in multi-well plates

Assays of behavior in model organisms play an important role in genetic screens, drug testing, and the elucidation of gene-behavior relationships. We have developed an automated, high-throughput imaging and analysis method for assaying behaviors of the nematode C. elegans . We use high-resolution optical imaging to longitudinally record the behaviors of 96 animals at a time in multi-well plates, and computer vision software to quantify the animals' locomotor activity, behavioral states, and egg laying events. To demonstrate the capabilities of our system we used it to examine the role of serotonin in C. elegans behavior. We found that egg-laying events are preceded by a period of reduced locomotion, and that this decline in movement requires serotonin signaling. In addition, we identified novel roles of serotonin receptors SER-1 and SER-7 in regulating the effects of serotonin on egg laying across roaming, dwelling, and quiescent locomotor states. Our system will be useful for performing genetic or chemical screens for modulators of behavior.

Model nematodes as a practical innovation to promote high throughput screening of natural products for anthelmintics discovery in South Asia: Current challenges, proposed practical and conceptual solutions

With the increasing prevalence of anthelmintic resistance in animals recorded globally, and the threat of resistance in human helminths, the need for novel anthelmintic drugs is greater than ever. Most research aimed at discovering novel anthelmintic leads relies on high throughput screening (HTS) of large libraries of synthetic small molecules in industrial and academic settings in developed countries, even though it is the tropical countries that are most plagued by helminth infections. Tropical countries, however, have the advantage of possessing a rich flora that may yield natural products (NP) with promising anthelmintic activity. Focusing on South Asia, which produces one of the world's highest research outputs in NP and NP-based anthelmintic discovery, we find that limited basic research and funding, a lack of awareness of the utility of model organisms, poor industry-academia partnerships and lack of technological innovations greatly limit anthelmintics research in the region. Here we propose that utilizing model organisms including the free-living nematode Caenorhabditis elegans, that can potentially allow rapid target identification of novel anthelmintics, and Oscheius tipulae, a closely related, free-living nematode which is found abundantly in soil in hotter temperatures, could be a much-needed innovation that can enable cost-effective and efficient HTS of NPs for discovering compounds with anthelmintic/antiparasitic potential in South Asia and other tropical regions that historically have devoted limited funding for such research. Additionally, increased collaborations at the national, regional and international level between parasitologists and pharmacologists/ethnobotanists, setting up government-industry-academia partnerships to fund academic research, creating a centralized, regional collection of plant extracts or purified NPs as a dereplication strategy and HTS library, and holding regional C. elegans/O. tipulae-based anthelmintics workshops and conferences to share knowledge and resources regarding model organisms may collectively promote and foster a NP-based anthelmintics landscape in South Asia and beyond.

Nemacol is a small molecule inhibitor of C. elegans vesicular acetylcholine transporter with anthelmintic potential

Nematode parasites of humans and livestock pose a significant burden to human health, economic development, and food security. Anthelmintic drug resistance is widespread among parasites of livestock and many nematode parasites of humans lack effective treatments. Here, we present a nitrophenyl-piperazine scaffold that induces motor defects rapidly in the model nematode Caenorhabditis elegans. We call this scaffold Nemacol and show that it inhibits the vesicular acetylcholine transporter (VAChT), a target recognized by commercial animal and crop health groups as a viable anthelmintic target. We demonstrate that it is possible to create Nemacol analogs that maintain potent in vivo activity whilst lowering their affinity to the mammalian VAChT 10-fold. We also show that Nemacol enhances the ability of the anthelmintic Ivermectin to paralyze C. elegans and the ruminant nematode parasite Haemonchus contortus. Hence, Nemacol represents a promising new anthelmintic scaffold that acts through a validated anthelmintic target.