Trent C et al. (1982) Worm Breeder's Gazette "map positions of genes that affect egg-laying in C elegans."

Horvitz HR, Tsung N, Trent C

[Worm Breeder's Gazette, 1982]

Mapping and complementation studies of egg-laying defective (egl) mutants have defined 34 new genes. These mutants are fertile, but show abnormalities in the time of onset or rate of egg-laying. Some of the mutants lay only late-stage eggs or larvae, becoming transiently bloated but eventually releasing most of their progeny. Others lay few or no eggs and become bags of worms in which progeny have hatched internally. The approximate map position of each new gene is indicated below. Mutants indicated by an allele number may be alleles of nearby egl or previously identified genes. [See Figure 1]

Casar, Jason et al. (2021) International Worm Meeting "Force sensitive upconverting nanoparticles as a direct, noninvasive assay for force generation by muscles"

Casar, Jason, Siefe, Chris, Dionne, Jennifer A., Lay, Alice, McLellan, Claire, Goodman, Miriam B.

[International Worm Meeting, 2021]

The digestive system relies heavily on muscles to breakdown, transport and expel material in order to provide the body the requisite nutrients to live. Additionally, activity of these muscles are key biomarkers of health status. Understanding the fundamental function of the digestive system and its dysfunction in aging and disease is hindered by a lack of suitable in vivo force sensors. Quantifying the forces generated in the alimentary lumen in vivo is currently not feasible through established mechanosensing platforms such as atomic force microscopy, traction force microscopy and Forster Resonant Energy Transfer (FRET)-based molecular strain sensors. To overcome that limitation, we are developing a microscale, biocompatible mechanosensing platform based on upconverting nanoparticles (UCNPs) that can rapidly and noninvasively readout micronewton scale forces within the intestinal and pharyngeal lumen of C. elegans. We synthesize lanthanide-doped ceramic nanoparticles (SrLuF:Yb,Er) embedded in polystyrene microspheres for efficient delivery. When excited in the near-infrared, these mechanosensing UCNPs have an emission spectrum that depends on pressure [PMID: 29927609; PMID: 31592655] and applied force. The ratiometric emission (red/green) increases by 25% with applied forces of 2 micronewtons as measured using dual confocal microscopy and atomic force microscopy. These particles are bright enough to image even the most rapid luminal pressure cycle in the worm (pharyngeal pumping, 5 Hz). We demonstrate the efficacy of using UCNPs to map luminal forces associated with feeding and digestion in wild-type adults. These measurements provide a time-resolved and direct indication of coordinated muscle function. We apply mechanosensing UCNPs concurrently with electrophysiological measurement of pharyngeal activity (ScreenChip), enabling assessment of the relationship between electrical activity and muscle function. We describe how these tools may be further developed into a high throughput platform for muscle function during aging and in C. elegans disease models, as well as how our UCNPs can be adapted to perform analogous measurements in other animals.

Stern MJ et al. (1989) Worm Breeder's Gazette "analysis of egg-laying muscle function by laser ablation."

Stern MJ, Horvitz HR

[Worm Breeder's Gazette, 1989]

The hermaphrodite sex muscles, comprising two types of vulval (vm1 & vm2) and two types of uterine muscles (um1 & um2), are essential for egg laying. Each of the four SM.x myoblasts give rise to one set of muscle cells comprising one of each type of muscle cell. We have determined which of these cells are required for egg laying. [See Figure 1] Specific cells were killed by laser ablation in mid-to-late L3 hermaphrodite larvae and the kills were confirmed 1-4 hours afterwards by Nomarski microscopy. The vulval muscles were visualized in young adults by polarized light microscopy to determine if specific ablated cells were being replaced by others. The animals were then scored for their abilities to lay eggs. In general, ablation of specific cells resulted in the absence of the corresponding muscle(s), although occasionally ablated cells appeared to be replaced. However, animals in which replacement appeared to occur and those in which it did not behaved identically in their abilities to lay eggs. From this result we conclude that although the muscle attachments can sometimes rearrange, their functions are not fully interchangeable. To determine whether all four sets are required for egg laying, various combinations of the SM.x myoblasts were ablated. Animals missing one set are essentially wild-type, while those missing three or all four sets fail to lay any eggs and form bags of worms. Animals with two sets on the same lateral side, and those with an anterior set from one side and a posterior set from the other side lay eggs almost as well as unablated animals. In contrast, animals with only two anterior or only two posterior sets bloat with eggs. Thus, it appears that some cells from at least one anterior and one posterior set are required for effective egg laying. We also ablated individual types of muscles in all of the sets, demonstrating that the vulval muscles are necessary and sufficient for normal egg laying and that the vm2's play a more important role than the vm1's. Animals missing all eight uterine muscles lay eggs apparently normally, while those missing all eight vulval muscles fail to lay any eggs. Ablation of the four vm2's results in egg-laying defective animals that form bags of worms, while ablation of the four vm1's results in animals that lay eggs almost as well as unablated animals. The vm2's are the only egg laying-muscles that receive direct innervation from the HSN neurons that drive egg laying. While it is possible that the defect caused by ablation of the vm2's is due to the inability for the remaining muscles to be stimulated to contract, the majority of animals missing the HSN's eventually lay their eggs and do not form bags of worms. Thus, the role of the vm2's in opening the uterine/vulval connection is probably also important in egg laying even in the absence of innervation by the HSN's.

David Weinkove et al. (2002) European Worm Meeting "The roles of developmental arrest, phosphoinositides, Type II PIP kinase and DAF-16 in the larval response to oxidative stress."

David R Jones, David Weinkove, Nullin Divecha, Jonathan R Halstead, Ronald H A Plasterk

[European Worm Meeting, 2002]

Since the appearance of terrestrial oxygen, it has been essential to deal with oxidative stress. For a nematode, the important issue is to lay eggs without germline damage. Rather than study the response in adults, for which it is probably too late to do anything useful, we have investigated how L1 larvae respond (1) developmentally, (2) genetically and (3) biochemically to a burst of hydrogen peroxide.

Argon Y et al. (1977) Worm Breeder's Gazette "sperm defective mutants."

Ward S, Argon Y

[Worm Breeder's Gazette, 1977]

We are characterizing 5 temperature sensitive (ts) fertilization defective mutants. These were isolated as ts steriles which lay unfertilized oocytes at 25 C. They all make normal amounts of sperm and are rescuable by mating with wildtype males, so their defects are in the sperm. The mutant hermaphrodites lay 150-220 unfertilized oocytes at 25 C and a small number (1-6%) of progeny. tsH4 and tsH3 lay a small number of defective zygotes as well. tsH2, tsH3 and tsH4 lay 30-60 unfertilized oocytes and 160-200 progeny at the permissive temperature. Hermaphrodite sperm are swept out of the spermatheca by the oocytes at a rate characteristic of each mutant. The males of the 4 mutants are sterile as well at 25 C as judged by mating them with 25 C grown tsH17 hermaphrodites which do not have any sperm. The male sterility is not due to defective mating because sperm are transferred to the uterus of the mated hermaphrodites. tsH24 males and tsH1 males stimulate oogenesis in the mated hermaphrodites, but tsH2, tsH3 and tsH4 males have so far failed to stimulate oogenesis although sperm are transferred. The temperature sensitive period (TSP) of tsH3, tsH4 and tsH24 has been determined. Although the onset of the TSP varies from 20 to 30 25 C-hours, they all extend throughout spermatogenesis and end at 44- 46 hrs, slightly after egg laying begins. tsH24 recovers fertility when shifted from 25 C to 16 C after spermatogenesis is finished. This suggests that the defective gene product is reversibly temperature sensitive and is in the sperm. The sperm of these mutants are being examined by electron microscopy to detect fine structural alterations and we hope to analyze them biochemically as well.

A Madi et al. (2002) European Worm Meeting "Proteome analysis reveals distinct molecular differences in developmental stages of wild type Caenorhabditis elegans"

S Mikkat, A Madi, B Ringel, M Ulbrich, M O Glocker, H-J Thiesen

[European Worm Meeting, 2002]

Caenorhabditis elegans is a well-known model organism of complex molecular processes such as programmed cell death of mammalian cells because of evolutionary conserved pathways. Our interests is to investigate normal development in wild type worms by proteome analyses to characterize stage-specific proteins and lay the ground for further comparisons and mutation studies. Up to now only proteome maps of populations with mixed stages have been constructed [1-3].

Venzon M et al. (2022) Cell Host Microbe "Microbial byproducts determine reproductive fitness of free-living and parasitic nematodes."

Venzon M, Das R, Burnett J, Cadwell K, Belasco JG, Park HS, Hubbard EJA, Devlin JC, Luciano DJ, Kool ET

[Cell Host Microbe, 2022]

Trichuris nematodes reproduce within the microbiota-rich mammalian intestine and lay thousands of eggs daily, facilitating their sustained presence in the environment and hampering eradication efforts. Here, we show that bacterial byproducts facilitate the reproductive development of nematodes. First, we employed a pipeline using the well-characterized, free-living nematode C.elegans to identify microbial factors with conserved roles in nematode reproduction. A screen for E.coli mutants that impair C.elegans fertility identified genes in fatty acid biosynthesis and ethanolamine utilization pathways, including fabH and eutN. Additionally, Trichuris muris eggs displayed defective hatching in the presence of fabH- or eutN-deficient E.coli due to reduced arginine or elevated aldehydes, respectively. T.muris reared in gnotobiotic mice colonized with these E.coli mutants displayed morphological defects and failed to lay viable eggs. These findings indicate that microbial byproducts mediate evolutionarily conserved transkingdom interactions that impact the reproductive fitness of distantly related nematodes.

Koelle MR et al. (1995) International C. elegans Meeting "egl-10 CONTROLS THE FREQUENCIES OF SEVERAL BEHAVIORS AND MAY REGULATE G PROTEIN SIGNAL TRANSDUCTION."

Koelle MR, Horvitz HR

[International C. elegans Meeting, 1995]

C. elegans lays eggs more frequently in the presence of a bacterial lawn than in its absence. To learn how the activities of the egg-laying neurons and muscles are regulated by environmental cues, we are studying two classes of mutants in which this regulation is disrupted: 1) mutants that fail to lay eggs despite having an apparently morphologically normal egg-laying system; 2) mutants that lay eggs more frequently than does the wild type. egl-10 loss-of-function mutants fail to lay eggs and also have reduced rates of locomotion and foraging. By varying the dosage of the egl-10 gene we found that the rates of these behaviors are proportional to the number of functional copies of egl-10. For example, animals carrying extra copies of the gene lay eggs more frequently and move faster than wild- type animals. We cloned egl-10 and determined its expression pattern using antibodies and GFP reporters. EGL-10 is present in the processes of many neurons, including the HSN neurons that control egg laying. The protein is also present in the vulval muscles, which control egg laying, and in body wall muscles, which control locomotion. Within muscle cells, EGL-10 protein is localized to what appears to be the sarcoplasmic reticulum. EGL-10 shows a distant sequence similarity to the yeast Sst2 protein. Sst2 is induced by and negatively regulates the G protein mediated signal transduction pathway that responds to mating pheromone. Genetic evidence suggests Sst2 may directly interact with the yeast G alpha subunit. By analogy, we postulate that EGL-10 may regulate a C. elegans signal transduction pathway that controls the frequencies of egg laying and other behaviors by modulating neural and muscle activity. Using degenerate PCR, we amplified nine egl-10 homologs from rat brain cDNA. EGL-10 thus appears to be a member of a large family of proteins that may regulate many G protein mediated signal transduction pathways.

Pribadi A et al. (2023) Elife "Dopamine signaling regulates predator-driven changes in Caenorhabditis elegans' egg laying behavior."

Rosales K, Pribadi A, Reddy KC, Rieger MA, Chalasani SH

[Elife, 2023]

Prey respond to predators by altering their behavior to optimize their own fitness and survival. Specifically, prey are known to avoid predator-occupied territories to reduce their risk of harm or injury to themselves and their progeny. We probe the interactions between <i>Caenorhabditis elegans</i> and its naturally cohabiting predator <i>Pristionchus uniformis</i> to reveal the pathways driving changes in prey behavior. While <i>C. elegans</i> prefers to lay its eggs on a bacteria food lawn, the presence of a predator inside a lawn induces <i>C. elegans</i> to lay more eggs away from that lawn. We confirm that this change in egg laying is in response to bites from predators, rather than to predatory secretions. Moreover, predator-exposed prey continue to lay their eggs away from the dense lawn even after the predator is removed, indicating a form of learning. Next, we find that mutants in dopamine synthesis significantly reduce egg laying behavior off the lawn in both predator-free and predator-inhabited lawns, which we can rescue by transgenic complementation or supplementation with exogenous dopamine. Moreover, we find that dopamine is likely released from multiple dopaminergic neurons and requires combinations of both D1- (DOP-1) and D2-like (DOP-2 and DOP-3) dopamine receptors to alter predator-induced egg laying behavior, whereas other combinations modify baseline levels of egg laying behavior. Together, we show that dopamine signaling can alter both predator-free and predator-induced foraging strategies, suggesting a role for this pathway in defensive behaviors.

Westlund B et al. (2004) Curr Opin Drug Discov Devel "Invertebrate disease models in neurotherapeutic discovery."

Stilwell G, Westlund B, Sluder A

[Curr Opin Drug Discov Devel, 2004]

Models that reproduce many of the cellular and molecular aspects of various human neurodegenerative disorders have been developed in the fruit fly Drosophila melanogaster and the nematode Caenorhabditis elegans. An understanding of the underlying molecular and genetic mechanisms of disease pathogenesis is being gained from studies utilizing the wealth of genetic and molecular tools available for these invertebrate model organisms. This review focuses on recent studies that lay a foundation for utilizing these disease models in drug discovery and for continued genetic dissection of disease mechanisms.