Baritaud, Mathieu et al. (2015) International Worm Meeting "Targeting mitochondria in muscular dystrophies through acting on ROS, mitohormesis and programmed cell death pathways ."

Kretz-Remy, Carole, Pierson, Laura, Baritaud, Mathieu, Walter, Ludivine, Mariol, Marie-Christine, Chazaud, Benedicte, Gieseler, Kathrin, Martin, Edwige

[International Worm Meeting, 2015]

Muscular dystrophies are characterized by muscle weakness and degeneration induced by genetic mutation of muscle structure or signaling components. The development of treatments against dystrophies is challenging, in part due to various primary genetic defects affecting different cellular functions. Nonetheless, many studies observed mitochondrial dysfonctions in muscle pathologies. Moreover, using a worm model of Duchenne Muscular Dystrophy (DMD) our team clearly demonstrated an implication of the mitochondrial key effectors Dynamin Related Protein-1, (DRP-1) and cytochrome c in the early process of muscle degeneration (MD). We are now focusing on Reactive Oxygen Species (ROS) and Programmed Cell Death (PCD) pathways to identify common mitochondrial disorders that contribute to MD in muscular dystrophies. We established different C. elegans models that mimic human muscular dystrophies such as Duchenne and Becker dystrophies, Limb-Girdle, Emery-Dreifuss or congenital muscular dystrophy. We revealed in the C. elegans model for DMD that MD can be reduced by treatments with the mitohormetic compound Paraquat (0,1mM) or the antioxidant compounds NAC and vitamin C. This observation suggested that ROS pathways mediated by mitochondria could be targets to reduce MD. In addition, our preliminary results indicate that these treatments are also efficient against MD in other C. elegans models for human muscular dystrophies. Moreover, using a gain of function mutation in the anti-apoptotic effector ced-9 gene (ortholog of Bcl-2) and RNA interference of key molecular actors of PCD linked to mitochondria: ced-3, ced-4, ced-13 and egl-1, we investigated whether specific mitochondrial PCD pathways are involved in MD. To validate our data obtained in C. elegans, we use human immortalized myoblasts from healthy or DMD patients. Preliminary data indicated that DMD myoblasts proliferate less and have a reduced fusion capacity during myogenic differentiation than myoblasts from healthy patients. Ongoing investigations examine mitochondrial pathways identified in C. elegans by challenging myoblasts for proliferation, cell fusion and oxidative stress sensibility.Our original approach using both worm models and human myoblasts, will allow us to establish whether manipulating mitochondrial pathways, particularly ROS signaling and PCD pathways can reduce progression of MD in muscular dystrophies.

Hongkyun Kim et al. (2002) West Coast Worm Meeting "A Genetic Study of Muscular Dystrophy in C. elegans"

Hongkyun Kim, Steven L McIntire

[West Coast Worm Meeting, 2002]

Muscular dystrophy (MD) is a common genetic disorder characterized by progressive muscle weakness and wasting. Mutations in dystrophin were identified as one cause of this disease in humans. Mutations in the C. elegans homologue of the dystrophin gene, dys-1, cause exaggerated bending of the anterior body during locomotion and muscle degeneration in a sensitized genetic background (1, 2).

Brewer, Jacob et al. (2017) International Worm Meeting "The HSN command neuron co-releases serotonin and NLP-3 neuropeptides to activate egg laying."

Brewer, Jacob, Koelle, Michael

[International Worm Meeting, 2017]

Major depression (MD), one of the most common mental disorders, is highly heritable and is commonly treated with selective serotonin reuptake inhibitors (SSRIs), which increase serotonin signaling in the brain. Yet, genome-wide association studies have failed to definitively implicate genetic defects in serotonin signaling as the cause of MD.1 We are studying the mechanism by which serotonin activates egg laying in C. elegans as a model for understanding the role of serotonin signaling in the activity of neural circuits. The C. elegans egg-laying system is well-suited for studying how serotonin functions in a circuit. The serotonergic HSN motor neurons initiate ~2.5 minute egg-laying active phases that occur every ~20 minutes. The evidence for this is that rhythmic HSN Ca2+ activity measured using a GCaMP reporter always accompanies egg-laying active phases, and optogenetic activation of HSN neurons is sufficient to stimulate activity of the egg-laying circuit.2 Interestingly, while egg laying requires the serotonergic HSNs3 and can be hyperactivated with an SSRI4, mutations knocking out serotonin biosynthesis have only weak effects on egg laying. This puzzling result draws striking parallels with the role of serotonin signaling in MD. We found that the HSNs release a neuropeptide in addition to serotonin to stimulate egg laying. The nlp-3 neuropeptide gene as well as the enzymes necessary for serotonin biosynthesis and release are all expressed in the HSNs. Knocking out either nlp-3 or serotonin biosynthesis caused mild egg-laying defects, but knocking out both caused a strong egg-laying defect that phenocopies that of animals lacking HSNs. Further, we optogenetically stimulated the HSNs and observed that the resulting egg-laying behavior is profoundly dependent on nlp-3, and is completely silenced in animals lacking both NLP-3 neuropeptides and serotonin. We propose that the HSN releases both serotonin and NLP-3 neuropeptides, which act cooperatively in a partially redundant fashion to stimulate egg laying, explaining the absence of strong egg-laying defects in mutants lacking serotonin. Serotonin receptors are found only on the muscles within this circuit, and sensitize them to contract in response to acetylcholine.2 We are currently analyzing the Ca2+ activity in the circuit to determine roles for NLP-3 neuropeptides in circuit activity. Co-release of serotonin and neuropeptides also occurs in the mammalian brain, and by analogy with the worm egg-laying circuit may be an important feature in explaining the absence of a strong genetic link between MD and serotonin. 1Flint and Kindler. Neuron. 2014. 2Collins, et al. eLife. 2016. 3Trent, et al. Genetics. 1983. 4Weinshenker, et al. J. Neurosci. 1995.

Katherine Schouest et al. (2007) International Worm Meeting "Development of a C. elegans model system for genetic and molecular dissection of epigenetic mechanisms underlying trinucleotide expansion disorders."

Charles Spillane, Katherine Schouest, Avril Coghlan

[International Worm Meeting, 2007]

Expansion of nucleotide repeats is now recognized as a cause of at least 20 different developmental and degenerative disorders in humans. Nucleotide-repeat expansion diseases can be classified into 3 main categories. The first disease category consists of loss-of-function recessive mutations due to disruption of gene expression (e.g. Friedrichs ataxia). The second category involves the expansion of nucleotide repeats (e.g. CAG) within exons, which are then translated into poly-amino acid (e.g. polyglutamine) stretches within the corresponding protein (e.g. Huntingtons Disease: HD). The third category involves expansions within non-coding regions of a gene, such as intronic or untranslated regions (e.g. Myotonic Dystrophy: MD). Model organisms are essential for the rapid advancement of genetic research on human diseases. C. elegans has already proven to be a powerful biomedical model in dissecting principles underlying diseases like HD or MD, as well as in revealing potential targets for therapeutic treatment. We are using C. elegans as a model organism to investigate epigenetic phenomena associated with nucleotide repeat disorders and to identify modifiers that regulate the size and rate of the expansions. To identify candidate genes for our research we have screened the C. elegans genome for trinucleotide repeats that have at least 12 trinucleotide repeats and a high level of purity, as these are most likely to undergo expansion or contraction. We have so far identified 20 such repeats located in C. elegans exons and 17 such repeats located within introns. To select one or more variable repeats for further analysis, the polymorphism of these repeats are currently being examined over 48 wild isolates of C. elegans. Once variable repeats have been identified, these alleles will be monitored through multiple generations in control animals and animals depleted of candidate modifiers via RNAi. The project will ultimately facilitate the understanding of the epigenetic phenomena that can cause nucleotide expansion disorders.

Xu, Yan et al. (2013) International Worm Meeting "SYD-1 mediates ventral axon guidance in the HSN neuron of C. elegans."

Xu, Yan, Quinn, Christopher

[International Worm Meeting, 2013]

During development axons navigate towards their targets, giving rise to the neural circuitry that controls behavior. During this navigation process, axons respond to extracellular cues that activate receptors to steer the axon along its trajectory. Guidance receptors are thought to be modular, forming in various combinations that have distinct functions. For instance, the UNC-40 receptor can function alone as a receptor for the UNC-6 guidance cue. Alternatively, UNC-40 and SAX-3 can function together, independently of UNC-6, as a receptor complex for the SLT-1 guidance cue (UNC-40/SAX-3 signaling) [1]. Since these different configurations of UNC-40 have distinct functions, they must have distinct signaling pathways. However, little is known about the pathway that mediates UNC-40/SAX-3 signaling. We have found that UNC-6 independent UNC-40 signaling can be mediated by SYD-1, an intracellular protein that contains a rhoGAP-like domain. We propose that SYD-1 may function with UNC-40 and SAX-3 to mediate UNC-40/SAX-3 signaling to promote the response to the SLT-1 guidance cue. We are currently characterizing the role of SYD-1 in guidance signaling and seeking to determine how it might be regulated to modulate UNC-40/SAX-3 signaling. [1] T.W. Yu et al., Nat. Neurosci. 5:1147-1154 (2002).

Beets, Isabel et al. (2015) International Worm Meeting "Large-scale deorphanization of C. elegans neuropeptide receptors."

Watteyne, Jan, Caers, Jelle, Van Sinay, Elien, Beets, Isabel, Peymen, Katleen, Schoofs, Liliane, Baytemur, Esra

[International Worm Meeting, 2015]

Neuropeptides are key modulators of adaptive behaviors and represent one of the largest groups of neural messengers, with over 250 bioactive peptides predicted in C. elegans. Most of them are thought to act by binding of G protein-coupled receptors (GPCRs). Despite the broad diversity of neuropeptides and their physiological effects, a handful of neuropeptide-specific receptors have been characterized and the majority of peptide GPCRs remain orphan receptors, i.e. have no known ligand.We are therefore undertaking a large-scale deorphanization initiative - the Peptide-GPCR project - that aims to match all predicted peptide GPCRs of C. elegans to their cognate neuropeptide ligand(s). Using an in vitro reverse pharmacology approach, more than 150 peptide GPCR candidates are expressed in a heterologous cellular system and screened with a library of all known and predicted C. elegans peptides of the established NLP and FLP families. Activation of each receptor is measured by a calcium reporter read out. We have found several novel and evolutionary conserved neuropeptidergic systems including signaling pathways related to mammalian neuromedin, neuropeptide FF, and neuropeptide Y systems. Our results provide insight into neuropeptide signaling networks, and present a scaffold for further unravelling how neuropeptidergic states modulate adaptive behaviors and physiology. Peptide GPCRs are screened randomly, but community members are invited to help us prioritize candidates and steer the project's progression via http://worm.peptide-gpcr.org.

Colavita A et al. (1997) International C. elegans Meeting "Suppressors of Ectopic UNC-5 Expression Identify a Novel TGF-b Involved in Axon Guidance in C. elegans."

Zheng H, Culotti JG, Krishna S, Padgett RW, Colavita A

[International C. elegans Meeting, 1997]

UNC-5 encodes a transmembrane receptor that guides migrating cells and pioneer axons away from ventral sources of secreted UNC-6 netrin guidance molecules in C. elegans. When ectopically expressed in the touch receptor neurons, which don!t normally respond to UNC-6, UNC-5 is able to confer UNC-6 responsiveness to their growth cones. This result forms the basis of a screen to look for mutations in components of the UNC6/UNC-5 signaling cascade - defects in components of this pathway should suppress the ability of ectopic UNC-5 to steer growth cones in response to UNC-6. This screen yielded mutants of 8 genes, one of which, unc-129, is a new uncoordinated mutant with axon guidance defects like those of unc-5 and unc-6 mutants. unc-129 was found to encode a novel member of the TGF-b family of secreted signaling proteins. unc-129-reporter transgenes are expressed in motorneurons and in dorsal muscles. Promoter bashing results indicate that the muscle expression is required for motor axon guidance; we are not yet certain whether motorneuron expression is also required. Ectopic expression of this TGF-b indicates that its spatial patterning is important for guiding cell and growth cone migrations. We are examining whether unc-129 acts on the UNC-6/UNC-5 signaling cascade as anticipated by the rationale for the suppressor screen, or whether it acts by an independent mechanism.

Dolinski CM et al. (1997) International C. elegans Meeting "PHYLOGENETIC IMPLICATION OF BUCCAL CAPSULE DEVELOPMENT IN SOME BACTERIAL FEEDING NEMATODES"

Baldwin JG, Dolinski CM, Thomas WK

[International C. elegans Meeting, 1997]

Bacterial feeding nematodes including Zeldia punctata (Rhabditida: Nematoda), and Caenorhabditis elegans differ profoundly in feeding adaptations and specifically in the rhabdions (cuticular thickenings), and associated cells lining in the buccal capsule. We are carrying out a range of tests to determine what rhabdions are evolutionarly homologous between the two species. Reconstruction of the buccal capsule and procorpus (pharynx) with transmission electron microscopy indicates that the lining of the buccal capsule of Z. punctata includes four sets of muscular radial cells ma, mb, mc, md in contrast the same region in C. elegans which has two sets of epithelial radial cells (e1, e3) and two sets of radial muscle cells (m1, m2). In Z. punctata ma is a set of three radial muscle cells each with 2 nuclei. In C. elegans m1 has the identical arrangement. Similarly, in Z. punctata mb is a set of 3 muscle cells each with one nucleus, similar to m1 in C. elegans. These findings could contradict all previous hypotheses of homology, and suggest instead that ma and mb in Z. punctata are homologous respectively with m1 and m2 in C. elegans. Ongoing additional tests of homology include comparative cell lineages and screening mutants to recognize genes involved in buccal capsule expression.

Garriga, G. et al. (2019) International Worm Meeting "Quantitative study of dopaminergic phenotypes via computer-aided video analysis."

Nelms, B., Garriga, G.

[International Worm Meeting, 2019]

Dopamine is an important neurotransmitter that regulates a myriad of brain functions ranging from motor control to memory and learning. Dysregulation of dopamine is associated with multiple disorders including Parkinson's disease (PD), attention deficit hyperactivity disorder (ADHD), addiction, and schizophrenia, among others. In order to better understand dopamine function at the molecular level, we are investigating the roles and regulation of dopaminergic genes using Caenorhabditis elegans (C. elegans) as a model system. We are conducting swimming induced paralysis (SWIP) assays using a computer-aided video analysis system, allowing us to collect more nuanced data to uncover new phenotypes and discover roles for genes involved in dopaminergic signaling. We have selected eight genes to focus on in this study. Each of these eight genes is highly enriched in dopamine neurons, based on RNASeq data from our laboratory, and mutant strains for these genes show accelerated swimming-induced paralysis when compared to the wild-type strain, N2, a phenotype characteristic of hyperdopaminergic signaling. Based on our computer-aided video analysis, we propose to gain more insight into specific rates and patterns of paralysis of these mutant strains in an effort to identify novel genes critical for dopaminergic functioning. Funding support from NSF CREST Grant #HRD1547757, NIH BD2K R25 Grant #1R25MD010396-01, and DOE Title VII Grant MD-HBCU #P382G090004.

Nakano, Shunji et al. (2015) International Worm Meeting "The C. elegans MAST Kinase Acts through Stomatin to Regulate Thermotaxis Behavior."

Sano, Ayana, Nakano, Shunji, Mori, Ikue, Ikeda, Muneki, Higashiyama, Tetsuya, Suzuki, Takamasa, C. Giles, Andrew

[International Worm Meeting, 2015]

C. elegans can sense and remember the environmental temperature and navigate themselves toward that temperature when placed on a thermal gradient. Although previous studies identified genes and neural circuits involved in thermotaxis, how C. elegans achieves this complex behavior still remains elusive. To further reveal the mechanisms underlying thermotaxis, we undertook a genetic screen to look for mutants defective in thermotaxis. We found that a null mutation in the gene kin-4, which encodes the C. elegans homolog of MAST (Microtubule Associated Serine Threonine) kinase, caused a cryophilic phenotype. Expression of kin-4 in the AFD thermosensory neuron rescued this defect. We also found that nj89, another isolate recovered from our screen, caused a thermophilic defect and suppressed the kin-4 mutant phenotype. nj89 is a gain-of-function mutation of mec-2, which encodes a stomatin-like membrane-associated protein previously shown to bind to microtubules and a DEG/ENaC (Degenerin/Epithelial Na Channel). To identify the behavioral components defective in these mutants, we set up a high-throughput tracking system to record thermotaxis behavior. Wild-type animals modulate the frequencies of omega and reversal turns. They also bias the angle of shallow turns to steer toward the cultivation temperature. We found that kin-4 and mec-2 mutants are defective in regulating reversal turn frequencies . Our results suggest a novel signal transduction pathway in which KIN-4/MAST kinase regulates MEC-2/Stomatin. Since both a mammalian MAST kinase and MEC-2 are known to associate with microtubules, KIN-4 might bind to microtubules and regulate the activity of MEC-2. Furthermore, given that MEC-2 modulates ENaC activity and that some ENaCs respond to temperature change, the KIN-4/MEC-2 pathway might regulate ENaC activity and control a process in the AFD sensory neuron, such as temperature sensing. Further study will assess whether ENaCs act with KIN-4/MEC-2 during thermotaxis and identify the molecular and neural mechanisms by which KIN-4/MEC-2 controls thermotaxis behavior.