Sengupta, T. et al. (2017) International Worm Meeting "Neurite position and synaptogenesis in the developing AIB neuron."

Kumar, A., Colon-Ramos, D.A., Moyle, M., Sengupta, T., Shroff, H.

[International Worm Meeting, 2017]

The position of a neuronal process (neurite) within a bundle or fascicle limits contact with other neurons to restrict potential synaptic partners. The AIB neuron of C. elegans travels through two distinct fascicles, forming presynaptic specializations in the posterior fascicle and postsynaptic sites in the anterior fascicle. The mechanism by which AIB positions its neurite in these two fascicles and restricts pre- and post-synaptic contacts to the appropriate neurons is not understood. We developed fluorescent markers to visually separate the two fascicles and label pre- and postsynaptic sites within the AIB neurite. Using diSPIM (dual-view inverted selective plane illumination microscopy), we visualized the process of outgrowth and synaptic polarity establishment in AIB during embryogenesis. By performing a forward genetic screen, we isolated candidate mutations that likely disrupt fascicle position and others that affect presynaptic polarity of the AIB neurite. Uncovering the causative genetic lesions for these mutants will provide insights into mechanisms that position neurites precisely within their fascicles to enable appropriate synaptic contacts.

Hawk, J.D. et al. (2017) International Worm Meeting "Integration of plasticity mechanisms within a single sensory neuron of C. elegans actuates a memory."

Calvo, A.C., Colon-Ramos, D.A., Hawk, J.D., Torruella-Suarez, M.L., Samuel, A.D.T., Aljobeh, A., Luo, L., Ren, I., Cook, N., Almoril-Porras, A., Greenwood, J.

[International Worm Meeting, 2017]

Neural plasticity-the ability of a neuron to change its cellular properties in response to past experiences-underpins the nervous system's capacity to form memories and actuate behaviors. How different plasticity mechanisms act together in vivo and at a cellular level to transform sensory information into behavior is not well understood. Here we show that in the nematode C. elegans two plasticity mechanisms-sensory adaptation and presynaptic plasticity-act within a single cell to encode thermosensory information and actuate a temperature-preference memory. Sensory adaptation enables the primary thermosensory neuron, AFD, to adjust the temperature range of its sensitivity to the local environment, thereby optimizing its ability to detect temperature fluctuations associated with migration. Presynaptic plasticity transforms this thermosensory information into a behavioral preference by gating synaptic communication between sensory neuron AFD and its postsynaptic partner, AIY. The gating of synaptic communication is regulated at AFD presynaptic sites by the conserved kinase nPKCe. Bypassing or altering AFD presynaptic plasticity predictably changes the learned behavioral preferences without affecting sensory responses. Our findings indicate that two distinct and modular neuroplasticity mechanisms function together within a single sensory neuron to encode multiple components of information required to enact thermotactic behavior. The integration of these plasticity mechanisms result in a single-cell logic system that can both represent sensory stimuli and guide memory-based behavioral preference.

Christensen, R et al. (2017) International Worm Meeting "Improved untwisting software for examining development in moving C. elegans embryos."

McCreedy, E, Guo, M, Mohler, W, Colon-Ramos, D.A., Levin, M, Duncan, W, Moyle, M, Bao, Z, Shroff, H, Wu, Y, Bokinsky, A, Christensen, R, Ardiel, E, Santella, A, Harvey, B

[International Worm Meeting, 2017]

The C. elegans embryo represents an excellent system in which to examine complex, systems-level developmental events, but rapid embryo movement and elongation confound inspection of events after embryos have begun twitching. This period of time encompasses numerous developmental processes, including cell specialization, neurite outgrowth and neuronal migration, and the beginning of functional activity in the nervous system. We recently reported (Christensen et al., eLife. 2015 4:e10070) a combined imaging and data analysis pipeline to enable developmental events during this time period to be studied. We now report improvements in our untwisting strain and data analysis pipeline. We have improved our untwisting strain by incorporating a worm surface marker (lin-26p::vab-10(actin-binding domain)::GFP; Gally C, et al., Development. 2009 136(18):3109-19) to provide more accurate information about the dorsal, ventral, and lateral boundaries of the developing embryo. We have adjusted the untwisting software to segment the surface marker, leading to less dorsal-ventral clipping and better capture of embryo structure in bent regions compared to the original untwisting algorithm. We have also incorporated better segmentation of seam cell nuclei when untwisting, leading to reduced lateral clipping in untwisted images, and have added the ability to convert 3D positions between twisted and untwisted space for any volume. We apply the improved untwisting software to track the position of seam cell nuclei and E lineage intestinal nuclei. We plan to use this software to track the position of all nuclei in the embryo from the beginning of twitching until hatching, as well as the morphological development of the C. elegans nervous system during embryogenesis.

Conroy, Brian et al. (2013) International Worm Meeting "The neuronal basis of food choice behavior in Caenorhabditis elegans."

Morabe, Maria, Chambers, Melissa, Conroy, Brian, Macfarlane, Rachel, Haynes, Lillian, Glater, Elizabeth

[International Worm Meeting, 2013]

Caenorhabditis elegans uses chemosensation to distinguish among various species of bacteria, their major food source (Ha et al., 2010; Shtonda and Avery, 2006). Although the neurons required for the detection of specific food-odors have been well-defined (Bargmann, 2006), less is known about the sensory circuits underlying the discrimination among the mixtures of odors released by bacteria. We plan to examine the neural machinery underlying bacterial preference among a diverse set of bacterial species. Does bacterial choice use one common neuronal mechanism or a diversity of mechanisms depending on the bacteria? Do some bacterial choices involve a single sensory neuron and others involve multiple sensory neurons? To address these questions, we are testing the food preferences of C. elegans for bacteria found in their natural habitats (kindly provided by Marie-Anne Felix, Institut Jacques Monod, Paris, France). We have found that C. elegans strongly prefers the odors of Providencia sp., Alcaligenes sp., and Flavobacteria sp., to Escherichia coli HB101, a commonly used food source for C. elegans. We have identified that the olfactory neuron AWC is necessary for this preference. We intend to test whether other amphid sensory neurons are also necessary for bacterial preference. In the future we will extend our analysis to other bacterial species to determine the diversity of the underlying neuronal mechanisms. Bargmann, C.I. (2006). http://www.wormbook.org. Ha, H.I., Hendricks, M., Shen, Y., Gabel, C.V., Fang-Yen, C., Qin, Y., Colon-Ramos, D., Shen, K., Samuel, A.D., and Zhang, Y. (2010). Neuron 68, 1173-1186. Shtonda, B.B., and Avery, L. (2006). J Exp Biol 209, 89-102.

Katz, Menachem et al. (2009) International Worm Meeting "CEP-sheath glia are required for normal locomotion in C. elegans."

Katz, Menachem, Lu, Yun, Shaham, Shai

[International Worm Meeting, 2009]

C. elegans glial cells share morphological, functional and genetic resemblance to their vertebrate counterparts. However, in contrast to vertebrate glia, C. elegans glia are not essential for neuronal survival, offering a unique opportunity to study the involvement of glia in the development and function of the nervous system in vivo. C. elegans CEP sheath glia (CEPsh) are bipolar cells that ensheath the dendrites of CEP neurons, and also envelope the nerve ring (the animal''s brain) extending processes that abut synapses. During development, these cells are involved in regulating axon guidance, dendrite extension, formation of the nerve ring (Yoshimura et al., 2008), and synaptogenesis (Colon-Ramos et al., 2007). However, post-developmental roles for CEPsh glia have not been studied. Here we demonstrate that animals in which the CEPsh glia were genetically ablated during the first larva stage display various motor defects including reduced speed of locomotion and intermittent periods of extended paralysis. Ablated animals also display high levels of small-angle turning, resulting in a spiral pattern of movement that restricts their movement to small areas on the plate. EM analyses of CEPsh glia-ablated animals reveal disorganization of the nerve ring, and swelling of neurons in the ventral ganglion. Thus CEPsh glia may play key homeostatic roles in the neuropil. To understand the molecular basis of CEPsh glia function we have begun to identify genes expressed in these cells using an mRNA-tagging method, with the aim of examining the roles of enriched genes in C. elegans locomotory behavior.

HA Tissenbaum et al. (1999) International C. elegans Meeting "Using model organisms to identify genes that affect life span"

L Guarente, HA Tissenbaum

[International C. elegans Meeting, 1999]

Previous work in C. elegans has identified a number of mutants that affect life span. We are trying to identify new components of the aging mechanism by isolating mutations in genes that are conserved in C. elegans and have previously been shown be important in the aging process of other eukaryotic organisms. 1) Werner Syndrome : People with Werner Syndrome (WRN) show many signs of premature aging (reviewed in Yu et al. 1997). The WRN protein is a member of the RecQ family of helicases. In yeast, mutations in the WRN homolog, SGS1 , cause yeast to age prematurely (Sinclair et al. 1997). Four members of the RecQ family have been identified in the C. elegans database. We are currently isolating knockout mutations of all four of the family members. As well, we are generating GFP fusions and doing RNAi to help elucidate the different functions of these four genes. These studies will help to determine if any of the four genes is the true WRN homolog in C. elegans and whether they function to control aging. 2) SIR2 homologs: Studies from yeast ( S. cerevisiae ) have identified the SIR proteins (SIR2, 3, 4) as important components for yeast aging (reviewed in Sinclair et al. 1998). SIR2, however, is unique among the SIR proteins in several respects including that it is highly conserved from yeast to man. There are two SIR2 homologs identified in the C. elegans database. To understand the role of C. elegans SIR2 in aging, we are generating knockout mutations and GFP fusions as well as performing RNAi. We are also using the candidate gene approach to identify mutants in the SIR2 homologs. References: Sinclair D.A., Mills K., and Guarente L. (1997). Science 277 :1313-6 Sinclair D.A., Mills K., and Guarente L. (1998). Annu Rev Microbiol 52 :533-60 Yu C.E., Oshima J., Wijsman E.M., et al. (1997) Am J Hum Genet 60 :330-41

Zhang H et al. (1996) East Coast Worm Meeting "Role of Cell Signalling in C. elegans Male Ray Development"

Zhang H, Emmons SW

[East Coast Worm Meeting, 1996]

Cell-cell interactions play an important role in C. elegans male ray development, but the nature of the signals involved is unknown. The presence of cell signalling has been demonstrated by cell ablation experiments. For example, if either of the seam cells V5 or V6, which give rise respectively to ray1 and to rays 2-6, is killed, its anterior neighbor cell will adopt the fate of the killed cell. An interaction between seam cell T, which generates rays 7-9, and its anterior neighbor, V6, can be demonstrated in a pal-1 mutant background. pal-1 is a homeobox transcription factor that is the C. elegans homolog of Drosophila caudal (1). In pal-1 homozygotes, V6 makes no rays; however, if the T cell is killed, V6 generates a normal complement of rays (2). Mosaic analysis has shown that the action of pal-1 to promote rays in the V6 lineage is due to its action within that lineage (1). This suggests that a ray-inhibiting signal normally passes from T to V6, but is blocked or overridden by the action of pal-1. The target of pal-1 may be the homeobox gene mab-5, since presumptive activation of mab-5 in a mab-5 gain-of-function mutant results in the generation of V6 rays in a pal-1 mutant background (1). In order to identify the signal from T that inhibits ray generation by V6 and to identify possible components of a mab-5 regulatory circuit, we are isolating extragenic suppressors of pal-1. We have obtained 19 alleles from about 4000 genomes screened. Some are very strong (more than 90% of V6 lineages make rays); others are weak (about 30% of V6 lineages make rays). In addition to resulting in recovery of V6 rays, most of these mutants have other phenotypes, such as ray fusion and abnormal ray morphology. Mapping and phenotypic characterization of these new mutations is in progress. 1 Waring, D.A & Kenyon, C Nature 350:712-715 2 Waring, D.A & Kenyon, C Cell 60:123-131

Peedikayil Kurien, Sonu et al. (2021) International Worm Meeting "Integration of neuronal connectivity, activity and synaptic plasticity drives sexually dimorphic learning in C. elegans"

Oren-Suissa, Meital, Peedikayil Kurien, Sonu

[International Worm Meeting, 2021]

Sexually dimorphic traits stemming from distinct processing of environmental cues bring about the holistic survival of the species and are mostly driven by sexual selection. However, the underlying mechanisms driving sex-dependent complex decisions remain largely unknown. Previous studies have shown that C. elegans hermaphrodites are able to shift their preference from attraction to aversiveness to a specific pathogenic bacterium Pseudomonas aeruginosa (PA14), after certain hours of exposure (Zhang et al, 2005). Using a modified version of this learned avoidance behavior, we show that C. elegans makes sexually dimorphic choices based on short past experiences. The hermaphrodites learn efficiently, as was previously shown. However, males do not learn to avoid PA14, even after training, thus retaining their initial preference. Using a blind testing paradigm, we show that larval stages of both sexes are unable to shift the preference, suggesting that maturation of nervous system is necessary for short term experience-based plasticity. By performing fast killing assays, we show that the lethality kinetics toward PA14 toxins is similar in the sexes, thus ruling out dimorphic susceptibility. To understand tissue specificity in developing a learned response, tissue specific sex-reversal experiments were performed and the importance of the nervous system was unraveled. In the same vein, we show that short term exposure does not involve signaling from the gut. Previous work has shown the importance of the interneuron AIY within several learning circuits (Ha et al, 2010; Jin et al, 2016). By analyzing AIY synaptic activity using fluorescently labelled RAB-3, we show that, upon short-term exposure, there is a decrease in synaptic activity, specifically, in an axonal region that forms connections with the interneuron RIA (Colon-Ramos et al, 2007). While this trend was prevalent in both the sexes, close examination of Ca2+ fluxes in the same region, using calcium indicators, reveal dimorphic responses to the odor of PA14. These results suggest that downstream encoding of short-term learning is sex-dependent and thus, its neuronal connectivity. To summarize, we present a model in which dimorphic processing of environmental cues, in a sex-specific manner, evokes diverse behavioral phenotypes that help shape the fitness of the species.

Gerbaba, Teklu et al. (2013) International Worm Meeting "Caenorhabditis elegans as a Model to Study Parasite-Induced Alterations in Host and Gut Microbiota Interaction."

Hansen, Dave, Buret, Andre, Wang, Xin, Gerbaba, Teklu, Rioux, Kevin

[International Worm Meeting, 2013]

Increasing evidence suggests a role for changes in gut microbiota in the pathophysiology of Irritable Bowel Syndrome (IBS) and Inflammatory Bowel Diseases (IBD). Acute gastroenteritis caused by enteric pathogens (including Giardia sp.) has been implicated in the onset or exacerbation of pathophysiology of these disorders, but the mechanisms remain obscure. The aim of this study is to develop a model system to investigate how an enteropathogen, Giardia, may lead to loss of gut homeostasis via alterations of host and gut microbiota interaction. Giardia and non-pathogenic E. coli (E. coli OP50, E. coli HB101) together resulted in paralysis and killing of C. elegans, while individually they had no effect on worm survival. Giardia conditioned media and E. coli are sufficient to kill C. elegans suggesting that killing is induced by secreted/excreted factor(s) released from Giardia, but worm killing induced by Giardia requires C. elegans direct contact with E. coli. Heat treatment of Giardia conditioned media failed to inhibit C. elegans killing, and Giardia only induced C. elegans killing in the presence of live E. coli. The effect of Giardia can also be observed in the presence of attenuated-virulence strains of C. rodentium (ESPF and MAP mutants), healthy individual gut microbiota, and inflamed site UC (Ulcerative Colitis) patient's colon microbiota, but Giardia has no effect in the presence of non-inflamed site UC patient's colon microbiota suggesting functional difference in the microbiota obtained from the two sites. The results mirror the synergistic effect of Giardia and normal gut micorbiota observed in germ free mice studies. Hence, C. elegans may be a useful model system for the study of Giardia, gut microbiota, and host interactions. In addition to providing new insights into the contribution of gut microbiota in the development of gastroenteritis, this system will provide a novel approach for the study of the role of gut microbiota in idiopathic functional gastrointestinal disorders.

E Froehli et al. (1999) International C. elegans Meeting "The APC-related gene apr-1 is required for morphogenesis of the embryo and generation of the vulval equivalence group"

A Hajnal, E Froehli

[International C. elegans Meeting, 1999]

apr-1 encodes the worm homolog of the human Adenomatous Polyposis Colon (APC) tumor suppressor gene. The APC mutations that are commonly found in human colon cancer delete the ß-catenin binding site of APC and result in the constitutive activation of ß-catenin in a wingless signaling pathway. These observations have suggested that APC may act as a negative regulator of wingless signaling. To study the role of apr-1 in worm development, we have isolated an EMS-induced deletion of 1414 base pairs ( apr-1(zh10) ) that removes the first, second and most of the third exon of apr-1. apr-1(zh10) embryos arrest at about the comma stage and fail to undergo elongation. The ventral hypodermal cells do not reach the ventral midline, resulting in defective ventral closure. A similar phenotype has been observed in hmp-2 (a ß-catenin ) mutant embryos (Costa et al., 1998). In addition, the anterio-lateral hypodermis is disorganized and expression of the HOX gene ceh-13 is down regulated in hypodermal and mesodermal cells of the anterior body region. During larval development, APR-1 is expressed in the six vulval precursor cells (VPCs) and in the seam cells. To study the role of apr-1 in vulval development, we have used two different approaches: (A) Tissue-specific RNAi by expressing antisense apr-1 cDNA under control of the Pn.p cell-specific lin-31 promoter. (B) Mosaic analysis by introducing wild-type apr-1 on an extrachromosomal array into an apr-1(zh10) mutant background and screening for animals that have lost the apr-1 transgene in the VPCs or their P cell precursors. VPCs that lack apr-1 activity loose their adherens junctions and adopt an undivided, non-vulval cell fate like Pn.p cells that are outside of the vulval equivalence group. Mutations in bar-1 (another ß-catenin, Eisenmann et al., 1998) and in the HOX gene lin-39 (Clark et al., 1993 and Wang et al., 1993) cause a similar phenotype. Furthermore, RNAi of apr-1 results in the down-regulation of lin-39 expression in the ventral cord of L1 larvae. In summary, our results suggest that wild-type apr-1 may function as a positive effector of the wingless signaling pathway to induce expression of the HOX genes ceh-13 in the embryo and lin-39 in the larva.