Research and publications

• Research projects

  Molecular and cellular pathways controlling nociception and its plasticity
  Status: Ongoing

  Start	01.11.2020
  End	31.10.2024
  Funding	SNSF  Open project sheet
  Nociception is the process of detecting and encoding noxious stimuli in the nervous system. Normal or abnormal activation of nociceptive pathways results in pain sensation, an unpleasant sensory experience linked to actual or potential tissue damage. Pain symptoms in human significantly decrease well-being and are still often not satisfactorily alleviated. Understanding the molecular and cellular processes modulating nociception, and in particular the nociceptive plasticity mechanisms occurring in normal and pathological conditions, may ultimately help to develop better pain management solutions. Progresses on this topic are hindered in mammals by ethical concerns, by the size and the complexity of their nervous system, and by the relative slowness of genetic approaches. Because they circumvent all these limitations, and because their nociceptive molecular pathways are remarkably conserved, invertebrates (such as Caenorhabditis elegans) have recently emerged as efficient complementary research models. The general goal of this project is to shed new light on the mechanisms underlying nociceptive plasticity by using the C. elegans model. The project leverages on robust thermal nociception plasticity paradigms in which innate heat-evoked noxious heat avoidance responses are modulated by repeated heat stimulations or by long-term starvation. We will make an extensive use of automated computer-assisted behavioral analysis platforms, which we have established in our laboratory and that allows high-throughput thermal avoidance analyses. The project has five specific aims: Aim 1 will seek to establish worm models for human pain genes. We will focus on genetic variants recently identified in genome-wide association studies (GWAS) and for which the mechanisms of action in pain pathways are largely unknown. In a previous screen with mutants in worm genes that are orthologous to these human pain genes, we identified 26 mutations that affected thermal avoidance and/or its plasticity. Using a series of heterologous expression and genetic rescue experiments, we plan to determine for which genes the modelling in worms is the most promising. Furthermore, we will characterize these genes and variants in more details, to understand how they control thermal nociception in worms. Aim 2 and 3 will address how Protein Kinase A and Calcineurin signaling each control thermal nociception plasticity. Mutations affecting these pathways in worms cause striking plasticity phenotypes and will be used here as entry points. In particular, we will determine the nature of the enzyme isoforms involved, their place and timing of action in the nervous system, their potential crosstalk with other pathways, and we will identify their downstream targets. To that end, we will engage a combination of approaches including genome editing to ablate specific gene isoforms or regulatory residues, cell-specific rescues and overactivation mutations, biosensors for in situ kinase activity monitoring, and phosphoproteomics. Aims 4 and 5 will address how thermal avoidance behaviors are regulated by neuropeptide communication to and from thermosensory neurons. Aim 4 will focus on how the FLP tonic thermonociceptor neurons can regulate long-term locomotory changes. Aim 5 will focus on how the acute heat-avoidance response triggered by AWC thermosensory neurons is modulated by food availability. For both aims, preliminary screens have identified candidate neuropeptides and receptors. In the present project, we will dissect the neural circuit involved by using tissue-specific gene knockout, functional manipulations with opto- and chemo-genetics, and in vivo calcium imaging. The significance of the project is twofold. First, it will advance our fundamental knowledge of the mechanisms controlling thermal nociception plasticity at the molecular, neuronal, and circuit levels, which will be essential for the development of research using the C. elegans model. Second, since the nociception mechanisms studied here are well conserved in higher organisms, the project will provide determinant insights on potential therapeutic targets in pain management, including by establishing tractable models for recently identified human pain genes, about which much remains to be discovered.

  C16.0013: Linking nociception and gene regulation in C. elegans neuroendocrine cells
  Status: Completed

  Start	01.01.2017
  End	31.03.2019
  Funding	SNSF  Open project sheet
  Nociception is the process of detecting and encoding noxious stimuli in the nervous system. It underlies responses such as pain, an important medical concern. In this project, we use a powerful genetic model, C. elegans, to explore a novel molecular mechanism that tunes nociception. Recently, we have discovered that the C. elegans CREB homolog-1 (CRH-1) transcription factor has an important role in neuroendocrine cells to control thermal nociception and resulting avoidance behavior. This finding offers an entry point to address the link between neuroendocrine functions and nociception, about which we know very little. The objective of the project is to identify the target genes of CRH-1 in neuroendocrine cells of C. elegans. To reach this goal, we engage cell-specific transcriptomics and DamID methods to identify relevant CRH-1 targets. Altogether, the project will provide critical new information on a previously unsuspected signaling mechanism controlling nociception. Since CREB signaling pathway is functionally conserved from C. elegans to human, this research will also provide cues for novel therapeutic strategies in pain management.

  Intracellular Signals Tuning Nociceptors in C. elegans (ItSTINGs)
  Status: Completed

  Start	01.11.2015
  End	30.06.2021
  Funding	SNSF  Open project sheet
  Nociception is the process of detecting and encoding noxious stimuli in the nervous system and underlies responses such as pain, an important medical concern. In this project, we will use a powerful genetic model, C. elegans, to explore novel molecular and cellular mechanisms tuning nociceptor neuron functions. We will focus on the Ca2+/Calmodulin-dependent protein kinase-1 (CMK-1) signaling. We have recently discovered that the basal cytoplasmic activity of CMK-1 in thermal nociceptors acts to maintain their sensitivity to noxious heat, whereas upon prolonged stimulation and desensitization, CMK-1 translocates to the nucleus, where it acts to reduce nociception. The specific goals of the project are: 1) To monitor the spatiotemporal CMK-1 activity pattern in nociceptors in vivo during both transient and long-term noxious heat treatments. To that end, we will engineer a genetically encoded optical CMK-1 activity sensor. 2) To identify upstream regulators of CMK-1 subcellular localization and activation. We will first use transgenic and pharmacological approaches to disrupt candidate Ca2+-signaling components and evaluate their impact on CMK-1 localization, CMK-1 activity, and thermal avoidance behavior. Second, we will perform a large scale RNAi screen to uncover genes required for CMK-1 translocation into the nucleus upon nociceptor desensitization. 3) To characterize the gene expression reprogramming taking place during nociceptor desensitization in response to prolonged stimulation. We will use nociceptor-specific transcript profiling with deep RNA-sequencing. Altogether, this project will combine a set of innovative and ambitious approaches in order to gain critical new information on a recently discovered signaling mechanism that tunes nociceptor functions. Since the Ca2+/Calmodulin-dependent signaling pathway is functionally conserved from C. elegans to human, this research will provide cues for novel therapeutic strategies to produce analgesia.

  Molecular and neural substrates of nociception and aversive behaviors in Caenorhabditis elegans
  Status: Completed

  Start	01.09.2014
  End	31.08.2018
  Funding	SNSF  Open project sheet
  Background: How animals sense environmental and internal cues, integrate information in the nervous system, and produce appropriate physiological and behavioral responses are fundamental questions in neurosciences. Nociception, the sensation of noxious stimuli, is an important process underlying aversive behaviors and the sensation of pain. Pain is a major patient concern in disease and there is an essential need for novel therapeutic solutions in pain management. Pain and temperature sensation are related processes. For example, the Transient Receptor Potential Vanilloid (TRPV) proteins form heat-gated channels with thermoreceptive and nociceptive functions. Any advance in our understanding of the molecular substrates, cellular processes, or emergent properties of the neural circuits involved in noxious stimuli detection and signal processing may help developing better pain killer drugs. Progresses on this topic are hindered in mammals by the size and complexity of the nervous system and could benefit from the use of simpler model organisms. General goal and experimental model: The long-term goal of our research is to shed new light on the mechanisms of temperature and pain sensation and associated behaviors, with the use of the Caenorhabditis elegans model organism. There is a remarkably good conservation of the genes regulating neural function between worms and humans (e.g. TRPV channel genes). Innate avoidance behaviors in response to noxious heat provide a readout of worm thermal nociception. Further advantages of this model organism include the availability of a complete nervous system wiring diagram and of efficient genetic techniques to monitor and manipulate single neuron activity. These features make C. elegans an ideal model to deepen our understanding of the processes at the molecular, cellular, neural circuit, and behavioral levels. Previous and current work: Previously, we established C. elegans as a powerful model to study thermal nociception and noxious heat-evoked aversive behaviors. First, we investigated the genetic basis of those processes. We developed new behavioral assays to (i) measure noxious heat avoidance performances and (ii) screen for defective mutants. By testing available mutations in candidate genes, we found that noxious heat avoidance is controlled by both TRPV-dependent and TRPV-independent pathways in C. elegans. Through a forward genetic screen, we isolated several new mutants defective in noxious heat avoidance and we are mapping those mutations using Whole Genome Sequencing. So far, most identified mutations in worm affect genes that have human orthologs, which highlights the interest of understanding how they function. Second, we established a computer-assisted platform for the quantitative analysis of behavior. We showed that noxious heat evoked-behaviors integrate multiple behavioral components and are subject to strong modulatory mechanisms, with some evidences for the implication of serotonin and insulin signaling. Third, by using the known connectivity diagram of C. elegans nervous system and combining results of mutant behavior quantification and cell specific rescue of mutations, we assembled a working model of the circuit implicated in noxious-heat evoked behaviors. As a whole, this work has established efficient tools for the analyses of thermal nociception and aversive behaviors and provided several entry points to further delve into the molecular and cellular mechanisms. Research objectives and experimental approaches: The present research project builds on our previous work in C. elegans to expand the research on the molecular and neural bases of nociception and aversive behaviors. The specific goals of the present project are to: A. Characterize the genes required for thermal nociception and avoidance behaviors B. Determine the role of food, insulin, and serotonin signaling in controlling heat avoidance C. Understand the functioning logic of the heat avoidance neural circuit D. Develop a “forward optogenetic” pipeline to generalize the screening of neuro-modulators Several approaches were engaged, including: • Computer-assisted analyses of behavior • Epistasis analysis to evaluate gene interactions • GFP reporter, cell specific rescue, and cell-specific RNAi to determine where different genes are acting • Optogenetics to artificially manipulate neuron activation and genetic ablation of neurons for functional evaluation • Calcium imaging with genetically encoded calcium indicators to monitor how neurons are activated by noxious stimuli in vivo and how their activation is altered by genetic mutations. Significance: The significance of the project is threefold. First, it will provide a comprehensive fundamental knowledge of the mechanisms controlling noxious heat aversive behaviors at the molecular, neuronal, and neural circuit levels. Second, it will establish an innovative and more universal method to screen for regulatory components functioning in specific neural pathways controlling behaviors. Third, the proposed approach could provide insights on potential therapeutic targets in pain management since the nociception mechanisms studied might well be conserved in higher organisms.

  Genetic Analysis of Temperature and Pain Sensation in Caenorhabditis elegans (follow-up)
  Status: Completed

  Start	01.12.2013
  End	31.08.2014
  Funding	SNSF  Open project sheet
  Genetic Analysis of Temperature and Pain Sensation in Caenorhabditis elegans (follow-up)

  Genetic Analysis of Temperature Sensation and Nociception in Caenorhabditis elegans
  Status: Completed

  Start	01.02.2012
  End	28.02.2014
  Funding	Europe  Open project sheet

  Genetic Analysis of Temperature and Pain Sensation in Caenorhabditis elegans
  Status: Completed

  Start	01.12.2010
  End	30.11.2013
  Funding	SNSF  Open project sheet
  Genetic Analysis of Temperature and Pain Sensation in Caenorhabditis elegans

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