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[
East Asia C. elegans Meeting,
2006]
Flavonoids produced in plants have anti-oxidative activity showing various effects on animal cells. Due to its simplicity, convenience and a complete genome sequence, C. elegans is an ideal animal model organism to investigate effects of flavonoids. Assay for resistance to oxidative stress was performed to measure anti-oxidative activity of flavonoids after inducing oxidative stress in worms by paraquat (1,1<SUP>,</SUP>-dimethyl-4-4<SUP>,</SUP>-bipyridinium dichloride hydrate). Synchronized worms were grown at 20°C until they reached at a gravid adult stage on plates containing each of quercetin, rutin hydrate, naringenin, naringin, hesperitin and hesperidin. Worms treated with flavonoids were transferred to 80 mM paraquat solution and incubated for 20 h at 20°C. Worms were then transferred onto a fresh agar plate, recovered for 1 h and scored for survival. Survival rates were measured by counting live worms. Hesperidin showed the relatively strong anti-oxidative activity when internal reactive oxygen species were generated by paraquat in C. elegans. This study was supported by KRF2004-F00019 (KRF) and the second BK21 (MOE)
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[
International Worm Meeting,
2011]
We assessed the interplay between body mechanics and touch sensitivity by modulating muscle tone with Channelrhodopsin-2 and measuring force thresholds with a novel force-clamp metrology. Touch sensation is poorly understood despite the prevalence of disrupted touch and associated pain in pervasive diseases like diabetes. C. elegans is an ideal model for touch with its six touch receptor neurons (TRNs) and behavioral response to gentle touch. Force applied to the body results in stress/strain of nearby TRNs, triggering opening of force-gated ion channels, cellular depolarization, and an avoidance response for sufficiently large forces. Previously, we developed a behavioral force-clamp metrology capable of applying nN-mN forces to moving L4/young adult animals (Park et al, Rev Sci Instr, in press). Using this metrology, we showed that wild-type (N2) animals respond to forces ³ 100 nN, revealing unprecedented mechanical sensitivity.
Previously, we showed that the three-layered outer shell (cuticle, hypodermis, and body wall muscle) plays a crucial role in filtering and transmitting applied forces (Park et al, PNAS 104:17376, 2007) and that body wall muscle tone regulates body mechanics (Petzold et al, Biophys J, in press). Now, we are testing the hypothesis that changes in body mechanics modulate touch sensitivity. To do this, we compare force-response curves in un-stimulated and hyper-contracted animals. Preliminary results show that larger forces are needed to evoke avoidance responses in hyper-contracted animals. We used light to manipulate body wall muscle contraction in transgenic animals expressing ChR2 under the control of a body wall muscle-specific promoter. This study provides a way to study the interplay between body mechanics and touch sensitivity in C. elegans and will further our understanding of the role of the outer shell in filtering and transmitting loads to the TRNs.
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[
International C. elegans Meeting,
1995]
Semidominant mutations in
unc-105 cause hyper- contraction and paralysis of body-wall muscles. Molecular analysis of
unc-105 by B. Schrank in this laboratory showed that the
unc-105 gene product is a member of the degenerin family and shares homology with amiloride- sensitive sodium channels in mammalian tissues. Thus, UNC-105 protein may be part of a sodium channel that functions in muscle. Significantly, the hyper-contraction and paralysis phenotype of
unc-105 mutants can be completely suppressed by mutations in
sup-20. Early work by Park and Horvitz showed that these suppressor mutations are special alleles of the gene, and that null alleles of
sup-20 cause embryonic lethality (E. -C. Park and H. R. Horvitz, 1986). We have obtained several lines of evidence that suggest
sup-20 mutations are allelic to mutations in
let-2, a gene encoding the
a2 chain of the basement membrane-specific type IV collagen (M. H. Sibley, J. J. Johnson, C. C. Mello, and J. M. Kramer, 1993). First, both genes map to the same interval and mutations in
sup-20 and
let-2 show non-complementation. Second,
sup-20 mutations can be rescued by a cosmid carrying the wildtype
let-2 gene. Third, a mutational change in
let-2 sequence has been identified in
sup-20 mutants. These data suggest a functional link between a potential membrane sodium channel and the extracellualr matrix surrounding the membrane. It is plausible that the gating of this channel involves interaction with the basement membrane, and such interaction may serve as a 'stretch receptor' to transduce external mechanical signals to regulate muscle contraction.
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[
Japanese Worm Meeting,
2000]
Protein kinases are well known to play important roles, such as cell-cycle controls, apoptosis and stress responses. A lot of genes containing protein kinase domain are identified in the genome of C. elegans. However, the biological functions of their majority are still unknown. In order to isolate novel kinases involved in meiosis and gametogenasis, at first, we selected about 100 putative kinase genes in the genome. Their expression level were examined by RT-PCR reaction with total RNA from young adult and L2 larval hermaphrodite. After that, some genes whose expression levels obviously increased in young adults were investigated by the RNA interference method. As a result, we found that T08D2.7 is required for gametogenesis. In this presentation, we will discuss the results of functions of some protein kinases.
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[
Development & Evolution Meeting,
2008]
A stem cell's decision between self-renewal and differentiation is governed by extrinsic stimuli from the surrounding microenvironment, or niche, as well as by intrinsic cues. In C. elegans, the distal tip cell (DTC) provides the niche for germline stem cells and maintains a "mitotic region" by Notch signaling (e.g. Kimble and Crittenden 2007). DTC number and dosage of the LAG-2 DSL ligand, which is expressed by the DTC, can affect the number of germ cells in the mitotic region (Dyan Vogel and Myon-Hee Lee). To investigate DTC niche function, we made a panel of fluorescent protein markers to visualize its subcellular structure in vivo. These include markers for the nuclear envelope, endoplasmic reticulum, Golgi, endosomes, and plasma membrane. Using membrane markers, we found that contact between the DTC niche and germ cells in the mitotic region is extensive. The DTC extends membrane processes that surround adjacent germ cells. The intimate contact between the niche and germ cells may provide a mechanism to physically anchor the distal-most germ cells within the niche and/or provide more localized signaling to maintain the germline stem cells. With a combination of DTC, sheath cell, and germ cell markers, we are examining the relationship between the extent of niche contact and the region of cells with stem cell potential. We are also using tissue-specific RNAi to test which genes are required in the DTC for regulation of germline stem cells.
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[
C. elegans: Development and Gene Expression, EMBL, Heidelberg, Germany,
2010]
In this study, we investigated the locomotion behavior changes at different developmental stages in Caenorhabditis elegans exposed to metals for 4h. No obvious differences could be observed in young adults exposed to examined metals, and only exposure to 100 mM of examined metals could signi?cantly decrease the locomotion behaviors of L4 larvae. In contrast, exposure to 50 and 100 mM of examined metals induced noticeable repression of locomotion behaviors at L1L3 larval stages, and a signi?cant decrease of locomotion behaviors could be observed in L1 larvae exposed to Pb and Hg, and in L2 larvae exposed to Hg at the concentration of 2.5 mM. Moreover, the L1-, L2-, and L3- larvae exposed to metals for 4h exhibited similar neuro behavioral toxicity manner to L4- larvae exposed to metals for 24h. Therefore, younger larvae showed more severe de?cits in neuro behavioral phenotypes than L 4 larvae and young adults in metal-exposed nematodes.
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[
International Worm Meeting,
2015]
One way to understand aging is to use unbiased approaches to profile molecular changes that occur with age, and determine the cause and effect of these changes. In this study, we identify changes in the proteome during aging in C. elegans using mass spectrometry-based proteomics. We find that secreted proteins and proteins expressed specifically in adult animals tend to increase in abundance with age. A previously uncharacterized subset of these age-increased proteins are expressed solely in the extracellular space of the adult uterus. These uterine proteins dramatically accumulate with age, but this increase in abundance is blunted in animals with an extended reproductive period. This suggests that age-induced infertility, an early event in the aging process, is at least partially responsible for the accumulation of proteins in the uterus. Furthermore, we find that uterine proteins rapidly turn over in young adult animals, but are removed much more slowly in old worms. Uterine proteins are not removed in young vulvaless worms, which indicates that egg laying or another means of exit through the vulva is necessary for the rapid removal observed in wild-type young animals. Finally, we show that uterine protein accumulation is toxic for the animal, as knocking down multiple uterine proteins simultaneously can extend lifespan. These findings represent a novel link between reproductive and somatic aging, in which age-induced infertility contributes to changes in the soma that are detrimental for survival. .
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[
International Worm Meeting,
2019]
Sexual interactions have a potent influence on health in several species, including mammals. C. elegans is well suited to study the impact of sexual interactions on lifespan, as males trigger the premature death of the opposite sex (hermaphrodites). Previous work has identified strategies used by males to accelerate the demise of the opposite sex. But whether counter-strategies evolved to protect hermaphrodites against males remains mysterious. Here, by shortening the time of sexual interactions, we discover that young C. elegans hermaphrodites are remarkably resistant to brief sexual encounters with males. Young hermaphrodites live a normal lifespan even after successfully mating with males, whereas older hermaphrodites succumb prematurely. Surprisingly, it is not their youthfulness that protects young hermaphrodites from males, but the fact that they have self-sperm. Feminized individuals that lack self-sperm succumb even at a young age after mating with males. Conversely, masculinized individuals that only have self-sperm live a normal lifespan even after mating with males at an older age. The beneficial effect of self-sperm is not due to fertilization. Instead, self-sperm protect the hermaphrodite soma via a sperm-sensing pathway that was previously known to act in the germline. This sperm-sensing pathway is also present in females, and activation of this pathway triggers somatic protection from the negative impact of males on feminized individuals. Interestingly, the role of self-sperm in protecting against the detrimental effects of males evolved independently twice in hermaphroditic nematodes. Thus, endogenous strategies to delay the negative effect of sexual interactions may represent a key evolutionary innovation to maximize reproductive success. While self-sperm are specific to hermaphrodites, they trigger pathways that are conserved in all species, and this could give new insights into the role of gametes in 'resetting' the aging clock. ** If possible, I would prefer that this abstract please be considered with the abstract submitted by Cheng Shi and Coleen Murphy ("Insulin-like peptides and the mTOR-TFEB pathway protect C. elegans hermaphrodites from Mating-induced Death")
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[
International Worm Meeting,
2007]
The study of mate-finding behavior in simple organisms, such as C. elegans, has helped us to understand how specific genetic and neuron networks regulate complex survival mechanisms. There has been a growing interest in using other nematode models, given that comparative analyses assist in elucidating conserved mechanisms and reveal adaptive differences between related species. Nematodes from the genus Pristionchus provide one such model, sharing many similarities with C. elegans yet having distinctly different modes of development and behavior. Previous studies have shown evidence of a mate-finding cue secreted by C. elegans hermaphrodites, which both attract and hold young adult males within close proximity (Simon and Sternberg, 2000). Here we describe evidence of a sexually-dimorphic mate-finding cue in both hermaphroditic and dioecious species from the genus Pristionchus. To assay the mate-finding cue, we have incubated young adult hermaphrodites/females in M9 for several hours and collected the solution carrying the secretions. We then placed a small volume of the collected cue in a 5mm diameter area on a bacterial lawn; placing an equal volume of control M9 in another 5mm diameter area on the same lawn. Ten young adult males are then placed onto the bacterial lawn per 30 minute trial and time spent in each of the 5mm diameter areas were recorded and compared. We have found that Pristionchus pacificus hermaphrodites secrete a cue that attracts and hold P. pacificus males within close proximity. We have also found that females from dioecious species P.lheritieri, P.pauli, and P.uniformis secrete a similar mate-finding cue.
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[
International Worm Meeting,
2021]
Key words Severe stress resistance, ageing, CeMbio, IIS, oxidative, heat. Abstract Stress resistance and longevity are robustly correlated across heat stress paradigms but not oxidative stress paradigms. In particular, severe stress resistance in ageing C. elegans markedly differs between exposure to oxidative and heat stress that kill wild type worms within a couple of hours (Benedetto et al. Aging Cell 2019). Severe stress resistance may engage multiple mechanisms such as basal stress handling vs adaptive stress response pathways, different stress transduction pathways, the ability to execute the organismal death program (Galimov et al. 2019), or protection/sensitisation conferred by the gut microbiota. To disentangle these and evaluate their relative roles in ageing worms, we are screening C. elegans mutant in combination with strains from CeMBio collection for resistance to 7% tert-butyl hydroperoxide (t-BHP) and 42oC heat-shock as severe oxidative stress and thermal stress paradigms, respectively, before contrasting these results with aged animals. We are performing these screens on young adults at first, before moving into aged worms. So far, we have found that the capacity to execute the organismal death pathway does not significantly impact severe stress resistance in young adults fed an OP50 diet. However, young adults fed on 48 different bacterial isolates displayed varying levels of severe heat and oxidative stress resistance, some of which were insulin/IGF1-signalling (IIS) pathway-dependent. We are currently investigating the basis of these differences. This poster will provide an overview of the methods used, current results and planned future work.