Ahn, Soungyub et al. (2015) International Worm Meeting "Novel regulators of RUNX transcription factor in Caenorhabditis elegans."

Chun, Jongsik, Swoboda, Peter, Ahn, Soungyub, Lee, Junho, Oh, Hyun-Seok

[International Worm Meeting, 2015]

RUNX transcription factors play pivotal roles in mammalian development and carcinogenesis. Proper expression and regulation of RUNX foster proper organismal development and prevent cancer development. We previously reported that RNT-1, the C. elegans sole RUNX homolog protein, is degraded by ubiquitin-proteasome system (UPS) and is stabilized upon acute oxidative stress response by repressing UPS. Nevertheless, other mechanisms of RNT-1 degradation remain elusive. To solve this question, we tried to find the novel regulator of RNT-1 stability and understand its mechanism. We isolated novel regulator genes involved in RNT-1 stabilization by random mutagenesis. Now we are characterizing RNT-1-stabilized mutants, and investigating the effect of the mutation on RNT-1 stability. Our study will contribute to further understanding of RUNX-involved development and carcinogenesis.

Choi, Shin S. et al. (2011) International Worm Meeting "Apoptosis-mediated toxicity of water stable carbon nanoparticles in Caenorhabditis elegans ."

Choi, Shin S., Cha, Yoon J.

[International Worm Meeting, 2011]

The application of nanoparticles in various fields has been evolved rapidly due to its authentic physicochemical properties. The potential biological or environmental toxicity of nanoparticles, however, has been frequently reported using in vitro systems. In this study, the toxicity of fullerene (nC60) and fullerol (C60-OH) in Caenorhabditis elegans was assessed through the measurement of lifespan, body size, and brood size. The water-stable colloids form of nC60 are prepared through the long-term exposure of fullerene, C60 in THF. We confirmed that the oral-administrated carbon nanoparticles were accumulated in the animals for several days after feeding the mixture of bacterial food and nC60 or C60-OH to the L4 larvas of C. elegans. The C60-OH reduced the viability of animals while no decrease in survival was found in the animals fed with nC60. We have also found that both nC60 and C60-OH reduced the reproduction of C. elegans. In order to illuminate the genetic mechanism of toxicity induced by those nanoparticles, the assessment of viability and fertility was carried out using the strains mutated in oxidative stress or programmed cell death regulators.

Takashi Murayama et al. (2006) East Asia C. elegans Meeting "Chemotactic response toward basic pH in C. elegans"

Ichiro Maruyama, Takashi Murayama

[East Asia C. elegans Meeting, 2006]

C. elegans responds to water-soluble chemicals such as ions and amino acids. We are especially interested in the response to OH^- as basic pH. In C. elegans, acid pH (H⁺) is sensed as a nociceptive stimuli, and basic pH (OH^-) is sensed as an attractive stimuli (Ward, 1973; Dusenbery, 1974). Sambongi et al. (2000) have shown some of amphid chemosensory neurons are responsible for acid pH avoidance by ablating these neurons. In general, however, a neural mechanism underlying OH^- response in any animals still remains to be explored. To investigate the OH^- chemosensation, we have developed an assay system. On the assay plate with a pH gradient from pH 7.0 to pH 10.0, wild-type animals move toward basic pH along the gradient. When some chemotaxis mutants were analyzed with this assay, osm-6, a sensory cilium-defective mutant, did not show any response to basic pH. In addition, some chemotaxis mutants have normal sensory cilia are found to be insensitive to the pH gradient. Now, we are analyzing some other chemotaxis mutants, and trying to isolate mutants showing irregular response to basic pH. Ward (1973), PNAS 70, 817. Dusenbery (1974), J. Exp. Zool. 188, 41. Sambongi et al. (2000), Neuroreport 11, 2229.

Li, Yuanbao et al. (2015) International Worm Meeting "Fatty acid two-hydroxylase (FATH-1) selectively regulates apical membrane trafficking in the C. elegans intestinal cells."

Zheng, Hanxi, Fu, Rong, Li, Yuanbao, Su, Xiong, Zhang, Huimin

[International Worm Meeting, 2015]

The hydroxylation of fatty acids (FA) at the C-2 position is the first step of FA a-oxidation and generates 2-hydroxy sphingolipids. However, the precise roles of FA 2-hydroxylation in whole cell homeostasis remains unclear. Fatty acid 2-hydroxylase (FA2H) is an enzyme that catalyzes the 2-hydroxylation of FAs to produce 2-hydroxy FAs (2-OH FAs). Here we use C. elegans intestine as the model and investigate the function of fath-1/C25A1.5, the worm homolog for mammalian FA2H enzyme, in protein transport and metabolism. GFP translational fusion reporter showed that C. elegans FATH-1 is expressed in most developmental stages and in most tissues. Loss of fath-1 expression results in severe growth retardation and shortened lifespan. Exogenous 2-OH FA rescue experiment revealed that FATH-1 primarily functions through its catalytic product (R)-2-OH FA. Tissue-specific RNAi knockdown showed that FATH-1 function is mainly required in the digestive tract but not in the epidermis. At the subcellular level, we found that loss of fath-1 expression induces endoplasmic reticulum stress and inhibits lipid droplets formation. Further analysis showed that loss of fath-1 selectively disrupts apical endosome recycling, but not early endocytosis or basal endosome recycling. By using the "click-chemistry" labeling method, we showed that 2-OH FA and derivatives are mainly enriched in vesicles close to the apical membrane of the intestinal cells and partially co-localize with apical recycling endosomes. Taken together, we propose that the (R)-2-OH FA produced by FATH-1 selectively marks apical endocytic vesicles to regulate protein transport and metabolism, therefore helps maintaining the cellular homeostasis.

Seo, Beomseok et al. (2015) International Worm Meeting "Telomere maintenance through recruitment of internal genomic regions."

Seo, Beomseok, Hills, Mark, Oh, Hyun-Seok, Lee, Junho, Sung, Sanghyun, Kim, Chuna, Shim, Jaegal, Choi, Rachael Mi Jung, Kim, Eunkyeong, Lim, Daisy S., Chun, Jongsik, Kim, Hyesook

[International Worm Meeting, 2015]

Telomere is a ribonucleoprotein complex that protects the natural ends of the linear chromosome. Telomere length is mainly maintained by telomerase, a reverse transcriptase that adds telomere repeat sequence. However recombination-dependent mechanism for telomere maintenance also exist in yeast and human cancer cells. In Caenorhabditis elegans, some of telomerase deletion mutant, trt-1(ok410), can maintain the telomere by alternative lengthening of telomeres (ALT). However the molecular mechanism of ALT in worms is largely unknown. In this study, we established stably maintained ALT survivors of worms that activate an ALT mechanism to escape from the sterility phenotype caused by telomerase deletion. By whole genome sequencing and mapping we concluded that mutation may not be required to maintain ALT telomere in these survivors. Interestingly, ALT survivors added either of two specific internal genomic regions as templates for ALT(T-ALT) according to their genetic backgrounds. A T-ALT sequence consists of telomere-like repeat sequence with unrelated sequence in between. T-ALTs had already been copied to a proximal telomere region of the same chromosome prior to ALT activation in nature, and were amplified interchromosomally by ALT activation. Here we propose a hypothesis that the existence of T-ALT structure in the proximal telomere may be one of the prerequisites for ALT activation..

Cha, Yun Jeong et al. (2013) International Worm Meeting "Biological behavior of carbon nanoparticles in Caenorhabditis elegans."

Choi, Shin Sik, Cha, Yun Jeong

[International Worm Meeting, 2013]

Although a number of researches on biological applications of nanomaterials have been investigated for the last ten years, the genetic mechanism behind a biological behavior of nanoparticles has not been fully understood yet. In this study, we illuminated a genetic interaction between carbon nanoparticles and physiological toxicity in Caenorhabditis elegans. Water stable suspension of fullerene (nC60) and hydroxyllated form (C60(OH)19-24) reduced survival ratio in adulthood of C. elegans resulting in diminished body growth and brood size in wildtype N2. In order to elucidate toxic mechanism of nanoparticles, the genes required for lower viability were discovered using mutations in apoptosis-, membrane permeability-, and stress-related regulators.

Ulzii, E. et al. (2019) International Worm Meeting "The roles of nhr-50 and nhr-99 in Satiety Quiescence."

Kamiya, M., Young, Y., Ulzii, E.

[International Worm Meeting, 2019]

C. elegans exhibits satiety quiescence that mimics many aspects of post-prandial sleep in mammals. The behavior depends on fat metabolism mediated by the SREBP-SCD pathway, an acetyl CoA carboxylase (ACC) and certain nuclear receptors (Hyun et al, 2016). We identified 28 nuclear receptors by microarray whose expression changes during refeeding following starvation. When individually knocked down by RNAi, 11 NRs among 28 alter both fat storage and satiety behavior. Among them, we focus on nhr-50 and nhr-99 for further study because they contain multiple transcription factor binding sites including DAF-16 and SKN-1, which regulate metabolism-dependent developmental decision and aging. RNAi of each of nhr-50 or nhr-99 results in enhanced satiety quiescence with reduced fat storage, suggesting these genes involve in communication between fat storage and the nervous system. When we tested outcrossed nhr-50 and nhr-99 mutants, the mutants show enhanced satiety quiescence consistent with the RNAi results. In addition, nhr-50 is expressed throughout the nervous system and the pharyngeal muscle, the relevant organs for regulation of feeding behavior. We are currently investigating how and where these NRs function to regulate satiety quiescence.

Valentini, Sara et al. (2009) International Worm Meeting "Little influence of iron homeostasis on aging in C. elegans."

Ackerman, Dan, Cabreiro, Filipe, Valentini, Sara, Gems, David

[International Worm Meeting, 2009]

During normal metabolism, O2 is converted into reactive oxygen species (ROS) such as O2, H2O2 and the particularly reactive OH. According to the oxidative damage theory, ROS-induced damage to biomolecules is a major cause of ageing1,2. The cellular free iron pool can contribute to ROS by catalyzing the Fenton reaction, where iron (II) is oxidized by H2O2 to iron (III), generating OH. Taken together, this suggests that iron homeostasis might protect against aging. Ferritins regulate the cytosolic concentration of iron by storing excess iron, and can provide protection against oxidative stress in some contexts 3,4. C. elegans has two ferritin genes, ftn-1 and ftn-2 (ref. 5). Long-lived daf-2 mutants show a ~50-fold increase in ftn-1 mRNA levels, raising the possibility that ftn-1 might contribute longevity assurance. We have therefore tested the role of ftn-1 in longevity assurance. We find that RNAi of ftn-1, alone or with ftn-2, does not affect daf-2 mutant longevity, nor does over-expression of ftn-1 increase lifespan. We are currently testing the effects of manipulation of ferritin levels on resistance to stress from iron (III) and H2O2. Overall, our results show that ferritin does not contribute to longevity assurance, and imply that iron homeostasis is not a critical determinant of aging in C. elegans. 1. Harman, J. Gerontol. 11, 298 (1956). 2. Beckman & Ames, Physiol. Rev. 78, 547 (1998). 3. Cozzi et al. J Biol Chem 275, 25122 (2000). 4. Balla et al. J Biol Chem 267, 18148 (1992). 5. Gourley et al. J Biol Chem 278, 3227 (2003).

Law, Wenjing et al. (2015) International Worm Meeting "Heterologous Expression in Remodeled C. elegans: A Platform for Monoaminergic Agonist Identification and Anthelmintic Screening."

Law, Wenjing, Komuniecki, Patricia, Komuniecki, Richard, Hapial, Vera, Ortega, Amanda, Wuescher, Leah

[International Worm Meeting, 2015]

Monoamines, such as 5-HT and tyramine (TA), paralyze both free-living and parasitic nematodes when applied exogenously and serotonergic agonists have been used to clear Haemonchus contortus infections in vivo. Since nematode cell lines are not available and animal screening options are limited, we have developed a screening platform to identify monoamine receptor agonists. Key receptors were expressed heterologously in chimeric, genetically-engineered Caenorhabditis elegans, at sites likely to yield robust phenotypes upon agonist stimulation. This approach potentially preserves the unique pharmacologies of the receptors, while including nematode-specific accessory proteins and the nematode cuticle. Importantly, the sensitivity of monoamine-dependent paralysis could be increased dramatically by hypotonic incubation or the use of bus mutants with increased cuticular permeabilities. We have demonstrated that the monoamine-dependent inhibition of key interneurons, cholinergic motor neurons or body wall muscle inhibited locomotion and caused paralysis. Specifically, 5-HT paralyzed C. elegans 5-HT receptor null animals expressing either nematode, insect or human orthologues of a key Galphao-coupled 5-HT1-like receptor in the cholinergic motor neurons. Importantly, 8-OH-DPAT and PAPP, 5-HT receptor agonists, differentially paralyzed the transgenic animals, with 8-OH-DPAT paralyzing mutant animals expressing the human receptor at concentrations well below those affecting its C. elegans or insect orthologues. Similarly, 5-HT and TA paralyzed C. elegans 5-HT or TA receptor null animals, respectively, expressing either C. elegans or H. contortus 5-HT or TA-gated Cl- channels in either C. elegans cholinergic motor neurons or body wall muscles. Together, these data suggest that this heterologous, ectopic expression screening approach will be useful for the identification of agonists for key monoamine receptors from parasites and could have broad application for the identification of ligands for a host of potential anthelmintic targets.

Gandotra P et al. (2000) East Coast Worm Meeting "Nuclear receptor genes in free-living and parasitic nematodes"

Crossgrove K, Maina CV, Gandotra P, O'Donnell M

[East Coast Worm Meeting, 2000]

The C. elegans genome project facilitated the discovery of the extensive representation of genes encoding members of the nuclear receptor (NR) superfamily of transcription factor proteins. The specific role of the vast majority of these genes in C. elegans remains unknown. NRs are required for developmental processes in a wide variety of multicellular organisms. One extensively studied example of the developmental role of NRs is in the control of molting and metamorphosis in Drosophila. Nematodes also undergo a series of molts during development and loss of function of at least one C. elegans NR (nhr-23) has been associated with molting defects. Nhr-23 is one of a number of NRs identified in C. elegans that have putative homologs in Drosophila. Another gene, nhr-85, was identified by sequence homology (Ann Sluder, personal communication) as a putative homolog of the Drosophila E75 gene. In Drosophila, E75 is induced by the molting hormone 20-OH ecdysone. 20-OH ecdysone can induce premature molting from the third to the fourth larval stage of the parasitic nematode Dirofilaria immitis (the causative agent of dog heartworm disease), suggesting that molting in this parasitic nematode may be under hormonal control similar to Drosophila. We have identified dinhr-6, a putative D. immitis homolog of the Drosophila E75 gene. The protein encoded by dinhr-6, is 83% identical to E75A in the DNA binding domain. Northern blot analysis suggests that dinhr-6 encodes multiple isoforms and is female-specific in adults. We are currently cloning the dinhr6 homolog from the human parasite Brugia malayi to expand our understanding of dinhr6 structure and function. However, working in parasite systems has certain limitations, particularly with the feasibility of genetic manipulation. Therefore, we are also attempting to characterize the structure and expression of the C. elegans nhr-85 gene with the eventual goal of using transgenic analysis and dsRNAi to understand the function of the nhr-85 gene. We discuss the potential of using C. elegans to help understand parasitic nematode development.