Choi, W. et al. (2017) International Worm Meeting "Chemosensory GPCR SRI-14 are required for concentration dependent odor preference in C. elegans."

Choi, W., Kim, Kyuhyung

[International Worm Meeting, 2017]

Animals must recognize and discriminate among thousands of chemicals in order to generate the correct behavioral response. Understanding basic design of a sensory system in simple animals gives the opportunity to elucidate detailed molecular and neural mechanisms underlying sensory responses in higher animals. C. elegans detects a large number of odorants via three neurons pairs including the AWA, AWB, and AWC, which elicit a multitude of olfactory behaviors (Bargmann, 1993, Cell). Previous genetic and behavioral experiments have identified set of signaling genes including olfactory receptors (Sengupta et al., 1996), but the knowledge is still limited. Specifically, the mechanisms of how the same odorants can elicit either attractive or aversive responses depending on the chemical concentration are not known yet. First, we are trying to construct a comprehensive map of odorants and their receptors in C. elegans. We screened 29 volatile chemicals that are not tested previously, and found that animals respond to 13volatiles. We further identified that the AWC neurons are required for chemotactic responses to these chemicals. We then performed candidate gene searches and found that the chemosensory GPCR mutants sra-13 and str-2 which express in AWC exhibit specific defects in chemotactic responses to 2-Furyl methyl ketone, Ethyl pyruvate, or 1-propanol, respectively. Interestingly, we also found that chemosensory GPCR sri-14 are required for both the attraction to low concentration DMTS and aversion to high concentration DMTS. The defect of DMTS chemotaxis in sri-14 mutants were restored when we expressed the wild-type sri-14 gene to the AWC neurons. Furthermore, for DMTS avoidance, not sri-14 gene in AWC expression but sri-14 gene in ASH expression fully rescue the defect of avoidance to high concentration DMTS, suggesting that the SRI-14 is required for both attraction and avoidance to DMTS and acts in AWC and ASH, respectively. We next found that Ca2+ response of AWC to low concentration DMTS was decreased in sri-14 mutants. We are currently measuring the Ca2+ response of ASH to high concentration DMTS compared to the sri-14, and trying to investigate the neural circuitry mechanism how the SRI-14 regulates both aversive and chemotactic behaviors in C. elegans.

Choi W et al. (2021) Curr Biol "A single chemosensory GPCR is required for a concentration-dependent behavioral switching in C.elegans."

Kim E, Cheon Y, Koo J, Moon C, Choi W, Choi H, Kim K, Ryu SE, Kim S, Park YJ

[Curr Biol, 2021]

Animals detect and discriminate countless environmental chemicals for their well-being and survival. Although a single chemical can trigger opposing behavioral responses depending on its concentration, the mechanisms underlying such a concentration-dependent switching remain poorly understood. Here, we show that C.elegans exhibits either attraction or avoidance of the bacteria-derived volatile chemical dimethyl trisulfide (DMTS) depending on its concentration. This behavioral switching is mediated by two different types of chemosensory neurons, both of which express the DMTS-sensitive seven-transmembrane G protein-coupled receptor (GPCR) SRI-14. These two sensory neurons share downstream interneurons that process and translate DMTS signals via distinct glutamate receptors to generate the appropriate behavioral outcome. Thus, our results present one mechanism by which an animal connects two distinct types of chemosensory neurons detecting a common ligand to alternate downstream circuitry, thus efficiently switching between specific behavioral programs based on ligand concentration.

S W Choy et al. (2005) International Worm Meeting "Characterization of a transcriptional repressor complex in male sensory ray patterning of C. elegans"

Y M Wong, S W Choy, K L Chow

[International Worm Meeting, 2005]

Mab21 is required in mouse embryonic turning, neural tube closure, mid-hind brain and eye differentiation. This gene is highly conserved in both vertebrate and invertebrate, and is required for the specification of the ray 6 identity and patterning of sensory rays. Characterization of this gene in C. elegans would therefore allow us to dissect critical molecular events in the organ developmental process of vertebrates. Epitasis analysis showed that mab-21 acts downstream of the BMP pathway to maintain the ray 6 features. SIN-3, a histone deacetylase associated molecule has been identified as a MAB-21 interacting partner. Mutant sin-3 animals displayed sensory ray abnormality, suggesting its biological relevance in ray differentiation. SIN-3 corepressor complex is highly conserved in vertebrate and invertebrate organisms. Using pharmacological and RNAi approaches, SIN-3 corepressor complex was found to be required in the patterning and formation of ray. Genetic interaction between mab-21 and sin-3 was demonstrated in double heterozygous and homozygous mutants. Moreover, SIN-3 interacting partners in C. elegans controlling the repression specificity were identified via a yeast two-hybrid screen. Characterization of these proteins is ongoing and their roles in ray cell identity will be discussed. In a parallel study, conservation of a role of Mab21 in eye development was observed. Our genetic characterization of a number of components relevant to eye formation suggests that although there is no analogous light sensing organ in worm, genetic components and their regulatory interaction in controlling sensory rays patterning are highly similar to those of vertebrate eye development. Therefore, delineation of the genetic pathway in the sensory ray patterning would help us to understand the developmental regulation of eye formation. In the future, we will study these corresponding homologs through genetic and molecular approaches. Results in these experiments may shed light on our understanding of disease states of sensory organ function. (This study is supported by Research Grants Council, Hong Kong.)

K Omata et al. (1999) International C. elegans Meeting "Characterization of the neural circuit of C. elegans: model analysis of the touch response"

F Yonezawa, K Omata, K Kawamura

[International C. elegans Meeting, 1999]

In order to characterize the neural circuit of C. elagans, we construct a simple model by making use of the data table completed recently by Oshio et al . [1]. We assume that the signal of a neuron is calculated by the product of the signals from the neighboring neurons, and we investigate the touch sensitivity to continuous stimuli described by sinusoidal functions as defined in the rage from 0.0 to 1.0. We calculate the responses of the motor neurons by changing the frequencies of the stimuli. In our calculations, we change only the frequency w PLM for the input signal to the sensory neuron PLM, while the frequency for the other sensory neurons ALM, AVM and PVM is fixed to be a same value w 0 . We show that the output signals from the motor neurons A and B oscillate in time. We measure the minima of the oscillation for each w PLM value. The plot of the minima versus w PLM shows different hehaviors for the case of the neuron A and B. As for the signals from the neuron A, the values of the minima are widely distributed between 0.0 and 1.0 for all w PLM . As for the signals from the neuron B, on the other hand, the features are different for different w PLM values. (a) In the high frequency region of w PLM / w 0 0.4, the oscillation is simple harmonic and there exists only one minimum value (I min = 0.0). (b) As w PLM / w 0 is decreased, another minimum appears at a certain frequency, and the bifurcation takes place discontinuously. This behavior is different from usual continuous bifurcation observed in nonlinear systems. After a few discontinuous branching occur, signals with five periods can be seen in the intermediate frequency region of 0.3 w PLM / w 0 w PLM / w 0 [1] K. Oshio et al. ; C. elegans synaptic connectivity data'', Technical Report, CCEP, Keio Future No.1 (1998).

Wang C et al. (2018) Nat Commun "Author Correction: Small-molecule TFEB pathway agonists that ameliorate metabolic syndrome in mice and extend C. elegans lifespan."

Zhao T, Oswald NW, Li Y, Lin R, Wang C, Jaramillo J, Zhou A, McMillan EA, Douglas PM, MacMillan JB, Huang G, Luo M, Gao J, Mendiratta S, Lin Z, Wang Z, Niederstrasser H, Posner BA, Brekken RA, White MA

[Nat Commun, 2018]

The originally published version of this Article contained an error in the spelling of the author Nathaniel W. Oswald, which was incorrectly given as Nathaniel W. Olswald. This has now been corrected inboth the PDF and HTML versions of the Article.

Nawa Y et al. (1985) Parasite Immunol "Defective protective capacity of W/Wv mice against Strongyloides ratti infection and its reconstitution with bone marrow cells."

Kotani M, Nawa Y, Kiyota M, Korenaga M

[Parasite Immunol, 1985]

The susceptibility of congenitally anemic, and mast cell deficient W/Wv mice to infection with Strongyloides ratti was examined. After a primary infection, W/Wv mice showed greater and more persistent peak larval counts than did normal littermates. Worm expulsion was also slower in W/Wv mice than in +/+ mice. Furthermore, difference in susceptibility was expressed as early as 24 h after infection, suggesting not only that protective mechanisms of the gut but also of the connective tissue were defective in W/Wv mice. Reconstitution with bone marrow or spleen cells from +/+ mice was effective in restoring the protective response in W/Wv mice, whereas thymocytes or mesenteric lymph nodes had no effect. Both connective tissue and mucosal mast cells were repaired in W/Wv mice after marrow reconstitution and infection. Since relatively long incubation period was required for the expression of such reconstituting activities, bone marrow cells seem to contain precursor cells of the effector and/or regulator cells.

Casiraghi M et al. (2004) Int J Parasitol "Mapping the presence of Wolbachia pipientis on the phylogeny of filarial nematodes: evidence for symbiont loss during evolution."

Guerrero R, Bandi C, Franceschi A, Pocacqua V, Gardner SL, Casiraghi M, Martin C, Bain O

[Int J Parasitol, 2004]

Wolbachia pipientis is a bacterial endosymbiont associated with arthropods and filarial nematodes. In filarial nematodes, W. pipientis has been shown to play an important role in the biology of the host and in the immuno-pathology of filariasis. Several species of filariae, including the most important parasites of humans and animals (e.g. Onchocerca volvulus, Wuchereria bancrofti and Dirofilaria immitis) have been shown to harbour these bacteria. Other filarial species, including an important rodent species (Acanthocheilonema viteae), which has been used as a model for the study of filariasis, do not appear to harbour these symbionts. There are still several open questions about the distribution of W. pipientis in filarial nematodes. Firstly the number of species examined is still limited. Secondly, it is not clear whether the absence of W. pipientis in negative species could represent an ancestral characteristic or the result of a secondary loss. Thirdly, several aspects of the phylogeny of filarial nematodes are still unclear and it is thus difficult to overlay the presence/absence of W. pipientis on a tree representing filarial evolution. Here we present the results of a PCR screening for W. pipientis in 16 species of filariae and related nematodes, representing different families/subfamilies. Evidence for the presence of W. pipientis is reported for five species examined for the first time (representing the genera Litomosoides, Litomosa and Dipetalonema); original results on the absence of this bacterium are reported for nine species; for the remaining two species, we have confirmed the absence of W. pipientis recently reported by other authors. In the positive species, the infecting W. pipientis bacteria have been identified through 16S rDNA gene sequence analysis. In addition to the screening for W. pipientis in 16 species, we have generated phylogenetic reconstructions based on mitochondrial gene sequences (12S rDNA; COI), including a total of 28 filarial species and related spirurid nematodes. The mapping of the presence/absence of W. pipientis on the trees generated indicates that these bacteria have possibly been lost during evolution along some lineages of filarial nematodes.

Chen J et al. (2016) Food Funct "Extracts of Tsai Tai (Brassica chinensis): enhanced antioxidant activity and anti-aging effects both in vitro and in Caenorhabditis elegans."

Xiang L, Liu X, Huang Z, Zhou X, Xiang Y, Zhang J, Chen J, Liu Y, He X

[Food Funct, 2016]

Tsai Tai is one of the most widely consumed Brassica vegetables in Asian countries because of its good taste and its nutritional benefits. This study evaluated the antioxidant capacity and possible associated health benefits of 3 Tsai Tai (Brassica chinensis) varieties, namely, Hon Tsai Tai, Pak Choi and Choi Sum. The DPPH radical scavenging ability and reducing power assays were performed to evaluate the in vitro activities of the extracts. Caenorhabditis elegans was used as an in vivo model for evaluation of beneficial health effects, including antioxidant activity and delayed aging. In vitro, the Hon Tsai Tai extract exhibited higher antioxidant activities than Pak Choi and Choi Sum, and the total phenolic contents were significantly correlated with the DPPH and RP values. In vivo, the three assayed Tsai Tai extracts significantly increased resistance against paraquat-induced oxidative stress with an increase in survival rates from 15% to 28% compared with controls. However, only the extract from Hon Tsai Tai significantly prolonged the lifespan of Caenorhabditis elegans, with an 8% increase in the mean lifespan with respect to controls. Further evidence of antioxidant protection was obtained by assessing ROS production via the DCF assay. The analyses of intracellular SOD activity and MDA content confirmed the existence of an antioxidant protective effect. These results suggest that Tsai Tai might serve as a good source of natural antioxidants, and in particular, Hon Tsai Tai could be explored as a potential dietary supplement to retard aging.

Lewis JA (1981) Worm Breeder's Gazette "Modified Ficoll Method for Cleaning Worms"

Lewis JA

[Worm Breeder's Gazette, 1981]

I have made two modifications in the Ficoll method I originally described in WBG, vol. 3, #2. First, all Ficoll solutions are made 0. 1 M in NaCl to avoid shocking osmoticalIy sensitive worms like unc-29( e1072). Second, after sedimenting worms through 15% w/w Ficoll 400 ( 15', 300 x g), the worms are diluted with an equal volume of 0.1 M NaCl and floated on 35% w/w Ficoll (15', 300 x g) before washing 2x with 0.1 M NaCl. The Ficoll sedimentation removes dead or degenerated worms, cuticles, bacteria. The flotation removes crystalline debris sometimes occurring in worm cultures. We also find that special care to pipette out the last residue of bacterial medium (e.g. 3XD) before resuspending bacteria for worm growth is most conducive to obtaining uncontaminated worms.

Li Z et al. (2018) Pak J Pharm Sci "Cellulase-assisted extraction and anti-ultraviolet activity of polysaccharides from the root of Flammulina velutipes on Caenorhabditis elegans."

Chen M, Lin L, Zhang Y, Wang T, Cui H, Wang C, Li Z

[Pak J Pharm Sci, 2018]

We investigated the cellulase-assisted extraction and anti-ultraviolet activity of water-soluble polysaccharides from the root of Flammulina velutipes on Caenorhabditis elegans. A Box-Behnken design experiment with three factors and three levels, including enzymolysis temperature, microwave time, and microwave power, was designed on the basis of the results of single-factor experiments. For improving the polysaccharide yield of F. velutipes root, the following optimal extraction conditions were used: 52.67C enzymolysis temperature, 80s microwave time, and 144 W microwave power. Under optimal conditions, the actual measured value of the yield was 2.01% (w/w) and the predicted value was 2.06% (w/w). One fraction (FRP-2) was isolated and purified, and its characteristics were analyzed. The average mean molecular weight of FRP-2 was measured to be 2.60x10⁵ Da, and its monosaccharide composition is mainly glucose. The sugar units are present both in the -configuration and -configuration. Moreover, FRP-2 exhibited certain anti-ultraviolet activity to C. elegans when the polysaccharide concentration ranged between 0.05mg/mL and 0.20mg/mL.