Liu, H. et al. (2017) International Worm Meeting "Sensorimotor integration regulates rapid decisions during chemotactic steering."

Zhang, Yun, Wu , Taihong, Yang, Wenxing, Liu, H.

[International Worm Meeting, 2017]

During active exploration, the sensory cue perceived by an animal is constantly patterned by the animal's own movement. Thus, to track the sensory target rapid decisions on locomotory outputs are often generated by integrating the sensory information with the ongoing motor state. However, the neuronal mechanisms that govern sensorimotor integration remains largely unknown. When C. elegans steers towards an attractive odorant, the repeated head undulations allow the nematode to sample the odorant gradient within the space spanned by the head swings. We find that one half head undulation that swings between the most dorsal and the most ventral head positions is the smallest unit to generate the maximum performance on steering. Thus, we characterize how the sensorimotor integration during the half head undulations generates the steering decision. Our previous studies show that the axon of an interneuron RIA exhibits two activity patterns, the compartmentalized activity that encodes and regulates dorsal-ventral head undulations and the synchronized activity that is evoked by sensory stimulations [Hendricks et al., 2012]. We now find that disrupting RIA function alters the rapid steering decisions during chemotaxis. By imaging the calcium transients in the RIA axons in restrained and freely moving animals, we find that the two activity patterns quantitatively encode the concentration of the stimulating odorant versus the amplitude of head undulations and that sensory-evoked synchronized activity suppresses the motor-encoding compartmentalized activity during chemotactic steering. This axonal sensorimotor integration transduces the spatial gradient of the odorant into the asymmetry of the RIA axonal activities. We further show that asymmetric axonal output of RIA biases the steering during movements towards the attractant. In addition, we show that experience modulates chemotactic steering by regulating the sensorimotor integration in RIA. Together, our results characterize how sensorimotor integration gives rise to rapid steering decisions during chemotactic movements.

Dana L. Miller et al. (2007) International Worm Meeting "Adaptation to hydrogen sulfide increases thermotolerance and lifespan."

Mark B. Roth, Dana L. Miller

[International Worm Meeting, 2007]

Hydrogen sulfide (H₂S), which is naturally produced in animal cells, has been shown to effect physiological changes that improve the capacity of mammals to survive environmental changes. We have investigated the physiological response of C. elegans to H₂S to begin to elucidate the molecular mechanisms of H₂S action. We show that nematodes exposed to H₂S are apparently healthy and do not exhibit phenotypes consistent with metabolic inhibition. However, we observed that animals exposed to H₂S had increased thermotolerance and lifespan and survived subsequent exposure to otherwise lethal concentrations of H₂S. Increased thermotolerance and lifespan is not observed in the sir-2.1(ok434) deletion mutant exposed to H₂S. However, mutants in the insulin signaling pathway (both daf-2 and daf-16), animals with mitochondrial dysfunction (isp-1 and clk-1) and a genetic model of caloric restriction (eat-2) all exhibit H₂S-induced increased thermotolerance. These data suggest that H₂S activates a pathway including SIR-2.1 that is separate from dietary restriction and insulin signaling that results in increased lifespan. Moreover, these studies suggest that SIR-2.1 activity may translate environmental change into physiological alterations that improve survival. It is interesting to consider the possibility that the mechanisms by which H₂S increases thermotolerance and lifespan in nematodes are conserved, and that studies using C. elegans may help explain beneficial effects observed in mammals exposed to H₂S.

Wang, Lin et al. (2017) International Worm Meeting "Dissecting the roles of the ADAM10 metalloprotease SUP-17 in the BMP signaling pathway in Caenorhabditis elegans."

Liu, Jun, Liu, Zhiyu, Shi, Herong, Wang, Lin

[International Worm Meeting, 2017]

BMPs (Bone Morphogenetic Proteins) belong to the TGFbeta superfamily of ligands, and mediate a highly conserved signal transduction cascade. Upon ligand binding, type II receptors phosphorylate type I receptors, which in turns phosphorylate R-Smads (receptor regulated Smads). Phosphorylated R-Smads then complex with co-Smad (common mediator smad) and enter the nucleus to regulate gene transcription with different co-factors. BMPs play important roles in developmental and physiological processes. Malfunction of the pathway in humans can cause various disorders, such as skeleton diseases, heart diseases and cancers. So it is critical to strictly regulate the level of BMP signaling spatiotemporally. Using a highly specific genetic screen, we have identified several modulators of the BMP pathway in C. elegans. These include the Neogenin homolog UNC-40 [1], two paralogous tetraspanin proteins, TSP-12 and TSP-14, and an ADAM10 metalloproteinase (A Disintegrin and Metalloproteinase 10) SUP-17 [2]. We use the CRISPR/Cas9 system and tagged the endogenous TSP-12, SUP-17 and UNC-40 proteins with different fluorescence tags. We found that TSP-12 is localized to the cell surface and intracellular vesicles, and that TSP-12 can bind to SUP-17 and promote its cell surface localization. We have genetic evidence and preliminary biochemical evidence showing that UNC-40 is one, but not the only, substrate of SUP-17 in BMP signaling. We are currently identifying additional substrate(s) of SUP-17 in BMP signaling. Our work highlights the importance of intracellular signaling and protease processing in the regulation of BMP signaling. [1] Tian C, Shi H, Xiong S, Hu F, Xiong WC, Liu J. The neogenin/DCC homolog UNC-40 promotes BMP signaling via the RGM protein DRAG-1 in C. elegans. Development. 2013;140(19):4070-80. doi: 10.1242/dev.099838. PubMed PMID: 24004951; PubMed Central PMCID: PMCPMC3775419. [2] Wang L, Liu Z, Shi H, Liu J. Two Paralogous Tetraspanins TSP-12 and TSP-14 Function with the ADAM10 Metalloprotease SUP-17 to Promote BMP Signaling in Caenorhabditis elegans. PLoS Genet. 2017;13(1):e1006568. doi: 10.1371/journal.pgen.1006568. PubMed PMID: 28068334; PubMed Central PMCID: PMCPMC5261805.

Abergel, Z. et al. (2017) International Worm Meeting "Adaptation of the nematode C. elegans to hypoxia and reoxygenation stress reveals an unexpected function of the neuroglobin GLB-5 in innate immunity."

Zuckerman, B., Zelmanovich, V., Abergel, Z., Abergel, R., Gross, E., Smith, Y., Romero, L., Livshits, L.

[International Worm Meeting, 2017]

Deprivation of oxygen (hypoxia) followed by reoxygenation (H/R stress) is a major component in several pathological conditions such as vascular inflammation, myocardial ischemia, and stroke. However how animals adapt and recover from H/R stress remains an open question. Previous studies showed that the neuroglobin GLB-5(Haw) is essential for the fast recovery of the nematode Caenorhabditis elegans (C. elegans) from H/R stress. Here, we characterize the changes in neuronal gene expression during the adaptation of worms to hypoxia and recovery from H/R stress. Our analysis shows that innate immunity genes are differentially expressed during both adaptation to hypoxia and recovery from reoxygenation stress. Moreover, we reveal that the prolyl hydroxylase EGL-9, a known regulator of both adaptation to hypoxia and the innate immune response, inhibits the fast recovery from H/R stress through its activity in the O2-sensing neurons AQR, PQR, and URX. Finally, we show that GLB-5(Haw) acts in AQR, PQR, and URX to increase the tolerance of worms to bacterial pathogenesis. Together, our studies suggest that innate immunity and recovery from H/R stress are regulated by overlapping signaling pathways.

Harnagel, Audrey et al. (2021) International Worm Meeting "Identifying Triggers for Pathogen Learning in C. elegans"

Harnagel, Audrey, Bargmann, Cori

[International Worm Meeting, 2021]

The ability to discriminate between nutritious and harmful food is essential to survival. As a result, learned avoidance to harmful food sources is conserved from invertebrates to humans. The mechanisms enabling the nervous system to associate sensory cues from a food source with an internal state of sickness to trigger aversive memory formation remain elusive. After prolonged exposure to pathogenic food, C. elegans can learn to avoid the pathogen upon subsequent encounter1. This learned aversion requires infection; non virulent forms of bacteria are not sufficient for memory formation. In response to exposure to pathogenic food, serotonin is induced in a pair of sensory neurons called ADF and remodels downstream circuits2. Learned aversion to pathogen requires serotonin signaling from ADF, suggesting that ADF serves as a site of integration for detecting bacterial cues and internal sickness caused by the pathogen. We seek to understand how internal state changes the coupling between sensory activation and serotonin release in ADF neurons. As a first step, we are using calcium imaging to examine ADF responses to bacterial cues in both naive and pathogen-exposed animals. ADF responds robustly to conditioned media from both pathogenic and non-pathogenic bacteria in a dose-dependent fashion, and ADF activity can be modulated by previous odor history. We are screening mutants using these quantitative parameters to assess ADF responses to direct chemosensory stimuli, indirect signaling from other sensory neurons, and signaling from non-neuronal tissues indicating bacterial infection. Our goal is to uncover cell-biological mechanisms through which ADF neurons mediate learned pathogenic behavior in C. elegans. 1. Zhang, Y., Lu, H., & Bargmann, C.I. (2005). Pathogenic bacteria induce aversive olfactory learning in Caenorhabditis elegans. Nature, 438(7065), 179. 2. Morud, J., Hardege, I., Liu, H., Wu, T., Basu, S., Zhang, Y., & Schafer, W. (2020). Deoprhanisation of novel biogenic amine-gated ion channels identifies a new serotonin receptor for learning. bioRxiv. doi: https://doi.org/10.1101/2020.09.17.301382.

David S Peal et al. (2001) International C. elegans Meeting "Chemical and Genetic Inhibition of Sulfation in C. elegans"

David S Peal, Laura L Kiessling

[International C. elegans Meeting, 2001]

In order to examine the process of sulfation in C. elegans, sulfation was inhibited chemically using sodium chlorate, and genetically using the process of RNA-mediated interference (RNAi). Sodium chlorate inhibition during early larval stages resulted in a dose-dependant developmental delay. BLAST searches of characterized sulfotransferases against the worm genome resulted in the identification of 4 putative sulfotransferases: C34F6.4 and F08B4.6 (previously identified: [1] and [2]), F40H3.5, and Y34B4A.e. RNAi of the putative N-deacetylase/N-sulfotransferase F08B4.6 resulted in "stacking" of eggs in the gonad, along with eggs laid at the 2- and 4-celled stage. RNAi of the putative hexuronic 2-O sulfotransferase C34F6.4 resulted in a shortened, bulbous gonad. These initial results indicate that sulfation may be important during development of C. elegans. [1] Shworak, NW, Liu, J, Fritze, LMS, Schwartz, JJ, Zhang, L, Logeart, D, Rosenberg, RD. JBC 272: 28008-19 (1997). [2] Kobayashi, M, Sugumaran, G, Liu, J, Shworak, NW, Silbert, JE, Rosenberg, RD. JBC 274: 10474-80 (1999).

Gary Schindelman et al. (2002) West Coast Worm Meeting "Characterization of the sperm transfer step of male mating behavior of Caenorhabditis elegans ."

Gary Schindelman, Allyson J Whittaker, Shahla Gharib, Paul W Sternberg

[West Coast Worm Meeting, 2002]

C. elegans male mating behavior involves the proper execution of a series of sub-behaviors culminating in the transfer of sperm to the hermaphrodite (Liu, KS and Sternberg, PW. 1995. Neuron 14:79-89). These sub-behaviors are: Response to hermaphrodite, backing, turning, vulval location, spicule insertion and sperm transfer. We are analyzing the genetic control of this stereotyped behavior as it may provide insight into sensory perception and nervous system function.

Rasika Kalamegham et al. (2004) East Coast Worm Meeting "EGL-26 belongs to the NlpC/P60 superfamily of putative enzymes and is closely related to a mammalian acyl transferase"

Wendy Hanna-Rose, Rasika Kalamegham

[East Coast Worm Meeting, 2004]

egl-26 was identified in a genetic screen to uncover mutants with vulval morphology defects. In egl-26 mutants the morphology of a single vulval toroid (vulF) is abnormal and a proper connection to the uterus is not made leading to the egg-laying defect. EGL-26 is a member of the NlpC/P60 superfamily of enzymes, which is characterized by a Histidine containing domain and a Cysteine containing domain (H-box and NC domain, respectively). EGL-26 along with other eukaryotic proteins belongs to a distinct subclass of NlpC/P60-related putative enzymes. The mammalian proteins lecithin: retinol acyltransferase or LRAT and H-ras revertant 107 or H-Rev107 are the most closely related to EGL-26. Both LRAT and H-Rev107 contain putative transmembrane domains in addition to the H-box and NC domains. Although EGL-26 contains no putative transmembrane domains, it is localized at the apical membrane of cells where it is expressed. Proper localization of LRAT within the retinal pigment epithelium is essential for its function. Significantly, an S-F substitution at amino acid 275 of EGL-26 found in the egl-26 (n481) allele causes mislocalization of an EGL-26::GFP fusion leading to general cytoplasmic expression as opposed to normal apical membrane localization. The corresponding Serine residue is conserved in both LRAT and H-Rev107. We are attempting to analyze the relationship between the mammalian proteins and EGL-26 by attempting a rescue of egl-26 mutants by expression of either LRAT or H-Rev107 or both. We plan to test the importance of membrane localization by restoring membrane localization to EGL-26n481 via addition of alternative membrane localization signals.

Schwartz, Hillel et al. (2013) International Worm Meeting "Developing Heterorhabditis nematodes as an experimental system for the study of mutualistic symbiosis."

Schwartz, Hillel, Sternberg, Paul

[International Worm Meeting, 2013]

Entomopathogenic nematodes of the genus Heterorhabditis are insect killers that live in mutually beneficial symbiosis with pathogenic Photorhabdus bacteria. Photorhabdus is rapidly lethal to insects and to other nematodes, including C. elegans, but is required for Heterorhabditis growth in culture and for the insect-killing that defines the entomopathogenic lifestyle. The symbiosis between Heterorhabditis and Photorhabdus offers the potential to study the molecular genetic basis of their cooperative relationship. We developing tools to make such studies more feasible: we have been studying multiple nematodes of the genus Heterorhabditis and developing tools for the molecular genetic analysis of Heterorhabditis bacteriophora. Many species of Heterorhabditis and variants of Photorhabdus have been isolated; some pairings show specificity in their ability to establish a symbiotic relationship. To better understand these interactions and other variations in the lifestyles of Heterorhabditis, we have sequenced H. indica, H. megidis, H. sonorensis, and H. zealandica; a H. bacteriophora genome sequence is available. A comparison of these closely related species may help us to identify mechanisms that regulate the response to bacterial interactions and to find variations that correlate with differences in lifestyle or bacterial compatibility. In addition to genomics, we are developing H. bacteriophora as a laboratory organism. H. bacteriophora grows well on plates, has been reported to be susceptible to RNAi and transgenesis, and can develop as a selfing hermaphrodite, and so should be a powerful system for the molecular genetic study of the aspects of biology to which it is uniquely well suited, most prominently symbiosis. This potential is severely diminished by inconvenient sex determination: the self-progeny of hermaphrodites are mostly females with some males; at low density, their progeny are almost exclusively females. We have screened for and isolated a constitutively hermaphroditic mutant for use in molecular genetic studies of symbiosis. This mutant also offers the opportunity to explore the basis of hermaphrodite sex determination in H. bacteriophora.

Schwartz H et al. (2010) Aging, Metabolism, Stress, Pathogenesis, and Small RNAs, Madison, WI "Towards a SNP map for Heterorhabditis bacteriophora"

Sternberg P, Schwartz H

[Aging, Metabolism, Stress, Pathogenesis, and Small RNAs, Madison, WI, 2010]

Heterorhabditis bacteriophora is a species of insect-parasitic nematode that lives in mutually beneficial symbiosis with pathogenic Photorhabdus luminescens bacteria. P. luminescens bacteria are lethal to insects and to other nematodes, including the soil nematode Caenorhabditis elegans, but are required for H. bacteriophora growth. The symbiosis between H. bacteriophora and P. luminescens therefore offers the potential to study the molecular genetic basis of their cooperative relationship. We are interested in developing tools to make such studies more feasible; in particular, we propose to generate tools for genetic mapping in H. bacteriophora. We will test independent isolates of H. bacteriophora to ensure that the isolates are cross-fertile. We will then examine the abilities of these isolates to grow on and to become infected with different wild-type and mutant Photorhabdus bacteria. From these tests we will select an isolate on which we will use next-generation high-throughput sequencing technology for the purpose of refining the existing draft genome sequence and for the creation of a SNP map. We anticipate that this SNP map will enable us and the wider insect-parasitic nematode community to identify induced mutations and natural variations affecting the interactions between H. bacteriophora nematodes and pathogenic Photorhabdus bacteria.