Yoon, Kyoung-hye et al. (2015) International Worm Meeting "The bacterial secondary metabolite violacein affects C. elegans development, fecundity and behavior."

Lee, Jin Il, Yoon, Kyoung-hye, Choi, Seong Yeol, Mitchell, Robert J.

[International Worm Meeting, 2015]

Bacteria use a variety of methods to combat predators and competitors in their natural environments. Bacteria are vulnerable to predator grazing, and can produce and secrete chemicals to deter predation. Nematodes are a major bacterial predator in nature, particularly rhabditid nematodes like C. elegans that reproduce in large numbers very quickly when they come upon an abundant food source. Violacein is a secondary metabolite that is secreted by various genera of soil and water bacteria. It is a bis-indole derivative that is easy to visualize due to its distinct purple color. Violacein has garnered interest due to its many therapeutic effects such as antimicrobial, anti-protozoal and anti-cancer properties, but its mechanism of action in these effects is not clear. We show that violacein is effective in preventing bacterial grazing by C. elegans. Violacein exposure results in decreased consumption of bacteria and avoidance of violacein-producing OP50, and this may account for the decreased bacterial grazing. To elucidate the mechanism in which violacein acts on C. elegans, we observed worms cultured in the presence of violacein. We found that worms cultured with either purified violacein or violacein-expressing OP50 showed slower development and decreased fecundity. In closer observation we saw several phenotypes including an expansion of the intestinal lumen, a decrease in intestinal volume, and retention of late-stage eggs in the gonad. In addition we were able to observe accumulation of purified deoxyviolacein, a precursor of violacein, in vesicles in the intestine. To identify the effect that violacein may have on intestinal cells, we used the autophagosome marker lgg-1::GFP and noticed increased autophagy in intestinal cells. Currently, we are testing various candidate mutants and various GFP indicator strains to further elucidate the molecular target of violacein.

Antonio, Jessica et al. (2021) International Worm Meeting "The role of FGF signaling in C. elegans' aging"

Yoon, Kyoung-hye, Antonio, Jessica, Chang, Jae Seung

[International Worm Meeting, 2021]

Fibroblast growth factors are conserved signaling peptides that are important for proper development, as well as regulating metabolic homeostasis. In C. elegans, there are two FGF orthologs, namely egl-17 and let-756. They both act on the one FGFR, egl-15, which is expressed in different tissues such as the hypodermis, muscle, neurons, and intestine. To investigate factors involved in healthy aging, we utilized the swimming assay, an established exercise paradigm for C. elegans. We looked at factors expressed in the muscle that may be affected by swimming exercise. During our initial investigation, we found that let-756 mRNA is increased after swimming. Surprisingly, while trying to investigate the role of let-756 in swimming exercise, we found that feeding RNAi in L4 worms actually increases maximum velocity of aging worms, an indicator of health. In addition, we found that let-756 RNAi treatment starting at L4 worms increases lifespan. Our study aims to investigate the role of FGF signaling and its downstream signaling pathway that is regulating the aging process. In answering this question, we want to investigate if this effect requires egl-15 in specific C. elegans tissues and what specific egl-15 subtype plays a role in the aging process.

Choi, Jae Im et al. (2017) International Worm Meeting "Identifying novel odor-receptor pairs in C.elegans."

Lee, Jin Il, Yoon, Kyoung-hye, Choi, Jae Im

[International Worm Meeting, 2017]

C. elegans is known to sense and respond to dozens of odors through G-protein coupled receptors expressed in three pairs of olfactory sensory neurons - AWA, AWB and AWC. In addition, worms display many olfactory behaviors including dose-dependent odortaxis, odor specificity, short and long-term odor memory, and odor-associative behaviors. One of these attractive odors, diacetyl, was shown to bind to its cognate receptor, ODR-10, by expressing the receptor in a heterologous cell line and demonstrating activity upon binding to diacetyl. However no other odor-receptor pairs have been definitively identified aside from ODR-10. In order to begin to identify new odor-GPCR matches in C. elegans, we conducted odortaxis assays to a set of 192 odors. We found that worms are highly attracted to 14% of these odors, mildly attracted to 10%, and show aversion to 7% of odors. We plan to identify which olfactory sensory neuron C. elegans uses to sense each of the odors using mutant analysis. To identify odor receptor pairs for AWC-sensed odors, we plan to express AWC-expressed ORs (Hsueh et al., 2016) in HEK293 mammalian cells, and determine their odor ligand using a cell-based reporter gene assay. We expect that these results will not only identify new odor-receptor pairs to study C. elegans olfactory behavior, but will contribute to our understanding of the genomic structure and evolution of olfactory receptors in the animal kingdom.

Lee, Tongyoung et al. (2019) International Worm Meeting "FMRF-like neuropeptide controls a C. elegans putative maternal behavior in a 3D environment."

Lee, Tongyoung, Lee, Jin I., Yoon, Kyoung-hye

[International Worm Meeting, 2019]

Parental behaviors are an essential evolutionary adaptation for the benefit of offspring survival. Although C. elegans mothers display the ultimate sacrifice in harsh environments by choosing to internally hatch, it is difficult to observe any outward care towards their young on a standard NGM plate. It is unknown, however, if C. elegans displays different behaviors in natural 3D environments such as rotting fruit and soil compost. To investigate the biology of C. elegans in 3D, we designed a cultivation habitat which we term NGT-3D and NGB-3D. Growth, brood size, and lifespan in NGT-3D are comparable with 2D NGM plate. Interestingly, wild-type worms display dwelling and egg-laying behaviors in a stereotypical pattern in NGB-3D that is not observed in regular plates: the mother worms spread the bacteria in a "nest" like pattern, remain near the edge of this nest, and move away from the bacteria to lay their eggs. We found that an FMR-like neuropeptide FLP-17 and its cognate receptor EGL-6 both play a role in this maternal egg-laying behavior. Although loss-of-function mutants of egl-6 and flp-17 show generally normal locomotion behavior, unlike wild-type, they do not move away from the bacteria to lay their eggs. When flp-17 mutants mothers are cultivated in NGT-3D, we find that they have lower reproductive fitness compared to N2. We are investigating the relationship between fitness and FLP-17-mediated maternal behavior. Finally, we will determine whether any environmental factor is related with these listed stereotypical behaviors and FMRF-like neuropeptide signaling. Interestingly, flp-17 is expressed in the BAG neuron involved in O2 and CO2 sensing. However, other candidate O2 sensing mutants still show a similar wild type-like behavior in 3D. In the future, we hope to describe a molecular and genetic picture of a maternal behavior circuitry in C. elegans.

Lee, Tong Young et al. (2017) International Worm Meeting "Observing the pattern of C. elegans egg-laying behaviors via 2D and 3D environment."

Lee, Tong Young, Yoon, Kyoung-hye, Lee, Jin Il

[International Worm Meeting, 2017]

The nematode C. elegans is one of the premier experimental model organisms today. In the laboratory, they display characteristic development, fertility, and behaviors in a 2D habitat. In nature, however, C. elegans is found in three dimensional environments such as rotting fruit. To investigate the biology of C. elegans in a 3D controlled environment, we designed a nematode cultivation habitat which we term the nematode growth tube or NGT-3D. Growth, brood size, and lifespan in NGT-3D are comparable with 2D NGM cultivation. Interestingly, we observe differences in patterns of feeding and egg-laying behaviors in 3D compared to 2D. We wonder if these differences affect the progeny in any way and are analyzing brood size and behavior patterns in the next generation. Additionally, we are screening through candidate mutants to identify any genes that are important for survival or fitness in 3D environments. Characteristic patterns of egg-laying and feeding behaviors observed in 3D might indicate a maternal behavior to benefit the survival and fitness of young in natural environments, and thus we plan to analyze the relationship between 3D egg-laying behaviors and another possible maternal behavior, internal hatching or worm bagging, that occurs in harsh environments. Overall, observing patterns of behaviors in a more natural 3D environment allows us to broaden our understanding of nematode biology and ecology

Lee, Tong Young et al. (2021) International Worm Meeting "Neuropeptides regulate a novel C. elegans oviposition behavior displayed in a three-dimensional environment"

Lee, Tong Young, Yoon, Kyoung-hye, Lee, Jin I.

[International Worm Meeting, 2021]

The C. elegans ecological niche is a complex and diverse three-dimensional environment found mostly in rotting fruit or soil compost. However, C. elegans behavior and physiology have mostly been studied in 2D culture in the lab. Previously, we designed a cultivation habitat which we term NGT-3D and NGB-3D in which growth, brood size, and lifespan in NGT-3D are comparable with 2D NGM plates. Using this 3D cultivation, we observed that the adult hermaphrodites spread the bacteria out from the center in a "nest" like pattern and remain at the edge of this nest. We then observed a novel stereotypical oviposition behavior in which the mother worms occasionally wander away from the bacterial nest, lay eggs, and then return to the bacteria. Using a candidate mutant analysis, we found that mutants defective in the neuropeptide PDF-1, as well as its cognate receptor PDFR-1 that regulates roaming behavior, were also defective in the novel 3D oviposition behavior laying eggs close to the bacteria. In addition, we identified mutants defective in the FMRF-like neuropeptide FLP-17 and its cognate receptor EGL-6 that together inhibit egg-laying were also defective in the novel 3D behavior. FLP-17 is expressed in the BAG sensory neuron, and the EGL-6 receptor expresses in the HSN neuron that regulates egg-laying. We showed that both egl-46 mutants that lack the BAG neuron as well as egl-1 mutants that lack the HSN neuron were also defective for the novel 3D oviposition behavior. To understand what cue may be causing mother worms to lay eggs away from OP50 in 3D, we found that 2D culture of C. elegans with a tiny "dot" colony of OP50 could elicit a similar egg-laying behavior in which the N2 mothers lay eggs far away from the bacteria. We found that low oxygen exacerbates the behavior, whereas high oxygen restores egg-laying in OP50. However, flp-17 mutants displayed defects in the oxygen-dependent egg-laying behavior. Finally, we tested whether defects in 3D oviposition behavior could induce decreased reproductive fitness in 3D and showed that flp-17 mutants have decreased brood sizes in 3D cultivation compared to 2D. Although low oxygen itself does not affect brood size, we found that cultivation with a high density of OP50 may be toxic to the young. Overall, we speculate that the novel 3D oviposition behavior may be a maternal behavior that increases the mothers' reproductive fitness.

Lee, Hee Kyung et al. (2021) International Worm Meeting "The role of mitochondria calcium uniporter in C. elegans odor learning"

Yoon, Kyoung-hye, Kwon, Saebom, Antonio, Jessica, Lee, Hee Kyung

[International Worm Meeting, 2021]

Calcium is essential for neuronal function - for activation, synaptic transmission, and also for modulating sensory adaptation and synaptic strength. Calcium concentration is carefully regulated in the cell by actively sequestering calcium into ER and mitochondria by transporters and calcium binding proteins. Mitochondrial calcium uniporter (MCU) is the transporter that permits calcium entry into the mitochondrial matrix, where, in addition to buffering cytosolic calcium, it regulates mitochondria-mediated cellular processes such as ATP synthesis and apoptosis. However, the role of MCU and mitochondrial calcium in neuronal function remains largely unknown. In this study, we sought to find the role of MCU and mitochondrial calcium in neurons in C. elegans, by using simple odor learning paradigms. We found that, whereas wild type strain shows significantly decreased chemotaxis index in response to 60 min pre-exposure, mcu-1 mutants show only a modest decrease. This was the case only for odors detected by the AWC sensory neuron, such as benzaldehyde and butanone. Restoring MCU-1 in all neurons and AWC resulted in normal adaptation, showing that MCU-1 in the sensory neuron is sufficient for adaptation. Using the heat shock inducible promoter, we found that mcu-1 is required during early larval development (egg or L1 stage), and restoring expression after L4 or adult stage did not improve odor learning. Surprisingly, we found that overexpression of mcu-1 in the AWC neuron resulted in delayed forgetting of the odor memory. This suggests that mcu-1 may regulate the plasticity of odor memory depending on its expression levels. We are currently investigating the downstream mechanism of our observations.

Kwon, Saebom et al. (2021) International Worm Meeting "Investigating the mechanism of the cell-nonautonomous roles of the nuclear hormone receptor NHR-49 in the nervous system of Caenorhabditis elegans"

Lee, Hee Kyung, Yoon, Kyoung-hye, Antonio, Jessica, Kwon, Saebom, Lee, Jin Il

[International Worm Meeting, 2021]

The central nervous system plays a key role in regulating and coordinating whole-body metabolism. In C. elegans, the nuclear hormone receptor NHR-49 is ubiquitously expressed and serve as an important regulator of fat metabolism. In addition to altered lipid composition, nhr-49 mutants display a pleiotropy of defects, including shorter lifespan, impaired starvation response, and increased susceptibility to oxidative stress and pathogenic bacteria. Interestingly, NHR-49 expression in the neuron alone is sufficient to nearly restore lifespan. In light of recent findings of the cell-nonautonomous effects of neurons in cell stress and energy homeostasis in C. elegans, we wondered whether NHR-49 function in the neuron alone could also reverse other known nhr-49 mutant defects. We confirmed that expressing NHR-49 exclusively in the neurons restores lifespan to a near-wild type level and found that it was also sufficient to restore resistance to gut commensal bacteria. In contrast, neuronal NHR-49 did not restore resistance to oxidative stress. We are currently trying to identify the circuitry and signaling mechanism of this neuron-to-periphery communication.

Choi, Jae Im et al. (2015) International Worm Meeting "The diacetyl receptor ODR-10 mediates a natural odor attraction between C. elegans and lactic acid bacteria grown on citrus fruit."

Choi, Jae Im, Kalichamy, Saraswathi, Lee, Jin Il, Yoon, Kyoung-hye, Yoon, Sung-Sik

[International Worm Meeting, 2015]

In the laboratory C. elegans displays odor related behaviors such as attraction, aversion, and adaptation. Worms express vertebrate-like G-protein coupled odor receptors in the AWA and AWC olfactory sensory neurons to sense attractive odors that are thought to be important for tracking bacterial food sources. However culture conditions in the laboratory are vastly different than those C. elegans encounters in the wild. Recent studies have shown that C. elegans is densely populated in rotting fruit and vegetation, which can be a rich source of bacterial bonanzas for nematodes. We wondered whether C. elegans exploits olfactory behaviors to track bacteria in rotting fruit. Using a combination of food microbiology, biochemistry, behavioral analysis and genetics, we elucidate a possible predator-prey relationship between C. elegans and lactic acid bacteria (LAB) in rotting citrus fruit. LAB produces the volatile odor diacetyl as an oxidized by-product of fermentation in the presence of citrate, and we confirmed this using a colorometric assay to determine diacetyl production in LAB grown on citrate media or citrus fruit. We show that C. elegans is attracted to LAB only when grown on citrate media or yuzu fruit, a citrus fruit native to East Asia, but not other fruits or grains such as apple, tomato or barley malt. We show that the attraction to LAB is mediated by the diacetyl odor receptor, ODR-10. In addition, adaptation to diacetyl odor results in attenuation of attraction behavior to LAB grown on citrate. We isolated a wild LAB strain and a wild C. remanei strain from rotten yuzu collected from a farm. The wild LAB strain produces diacetyl when grown on citrate media or yuzu, and C. elegans attraction to the wild LAB grown on yuzu is mediated by ODR-10. We also demonstrate that the wild C. remanei is attracted to wild LAB when grown on citrate media or yuzu. These results not only identify an ecological function for a C. elegans olfactory behavior, but contribute to the growing understanding of the molecular and genetic basis for natural ecological phenomena.

Tellez-Arreola, Jose L et al. (2019) MicroPubl Biol

Gonzalez-Montiel, Simplicio, Valdez-Calderon, Alejandro, Martinez-Torres, Ataulfo, Tellez-Arreola, Jose L, Hernandez, Adan

[MicroPubl Biol, 2019]

Infections by helminths are one of the major health problems in developing countries. Fast adaptation of parasitic organisms has conferred resistance to drug therapies used for decades (Burns et al., 2015), causing a threat to control worm parasites and generating an urgent need for new emergent molecules with therapeutic potential, in particular for nematodes. The nematode Caenorhabditis elegans is phylogenetically-related to parasitic species of helminths in which high throughput assays are challenging; thus, this species is an excellent model to study and evaluate novel anthelmintic drugs (Gilleard, 2004; Yoon et al., 2006). One interesting molecular target for drug development are the GABA receptors of parasitic helminths which are evolutionarily preserved in invertebrates and vertebrates and are present in C. elegans (Castillo et al., 1967; del Castillo et al., 1964; Jorgensen, 2005). GABA receptors from C. elegans are ionotropic channels that belong to the Cys-loop superfamily of ligand gated ion channels widely spread in multiple species, including humans (Olsen and Sieghart, 2008).