Mario de Bono (2003) International Worm Meeting "Evolutionary and behavioural perspectives on nematode aggregation"

Mario De Bono

[International Worm Meeting, 2003]

Aggregation behaviour has been reported in many species of nematodes, including vertebrate gut parasites such as Trichostrongylus colubriformis1(Strongylida), plant parasites such as Tylenchorhynchus martini2 (Tylenchida) and free-living species such as C. elegans3(Rhabditida). This prompted us to look for aggregation behaviour in other nematode species. Under our standard assay conditions, wild isolates of C. remanei (n=6 isolates) all aggregated to similar extents as social isolates of C. elegans. In contrast, most C. briggsae isolates (n=8) showed only weak aggregation behaviour, and one isolate, AF16(Gujarat), behaved like a C. elegans solitary feeder. The Caenorhabditis sp. CB5161 also behaved like a solitary feeder. Interestingly, all these strains encode NPR-1 215F, the NPR-1 isoform associated with social feeding in C. elegans. This suggests that the genetically dominant npr-1 215V allele arose in C. elegans by a gain-of-function change. It also suggests that other changes, either in npr-1 or in other genes, account for natural variation in aggregation behaviour in these strains. Outside Caenorhabditis, I have seen aggregation behaviour in Rhabditis blumi (DF5010), Rhabditella axei (DF5006), Pellioditis typica (DF5025) and Pelodera teres (EM437). Further work is needed to establish if these behaviours are homologous or the result of convergent evolution. However one possibility is that the ability to aggregate is ancient in nematodes. This would be consistent with our genetic studies, which suggest remarkable complexity in the regulation of aggregation behaviour4,5. To gain insights into how C. elegans aggregate, we are filming social and solitary animals and quantitatively comparing their behaviours as they feed and encounter each other on the E. coli lawn. Since E. coli may not be an important source of food for C. elegans in the wild, we have also examined behaviour on soil bacteria more likely to be a dietary staple of the worm, including Pseudomonas paucimobilis, P. chlororaphis, P. putida, P. fluorescens, Agrobacterium radiobacter, Burkholderia cepacia, and B. subtilis. Social strains aggregated on all these bacterial species, whereas solitary animals did not. 1 Jenkins et al., 1986; Parasitology 93: 531-537; 2 McBride and Hollis 1966, Nature 211, 545-546; 3 Randy Cassada, WBG 9(3) 29; 4 de Bono et al., 2002, Nature 419: 899-903; 5 Coates and de Bono, Nature 419: 925-929.

Zarkower D et al. (1994) Worm Breeder's Gazette "mab-3 YAC Rescue"

De Bono M, Hodgkin JA, Zarkower D

[Worm Breeder's Gazette, 1994]

mab-3 YAC rescue David Zarkower, Mario de Bono, and Jonathan Hodgkin MRC Laboratory of Molecular Biology, Cambridge, England

Mario de Bono et al. (2001) International C. elegans Meeting "Activity of nociceptive neurons is required for social behaviour in C. elegans"

Cori Bargmann, Mario De Bono, David Tobin

[International C. elegans Meeting, 2001]

Wild isolates of C. elegans show one of two foraging behaviours. Solitary strains, like N2, feed alone. By contrast social strains aggregate and feed together (R. Cassada, wbg 9(3): 29; Hodgkin and Doniach, 1997; de Bono and Bargmann 1998). This natural variation in behaviour is principally due to differences at the npr-1 locus. npr-1 encodes a 7 TM receptor of the neuropeptide Y family, and null mutants at this locus display strong social behavior. To explore the signals required for social behaviour, we asked whether social strains aggregate in the absence of food. We find that even when dispersal is prevented, natural social isolates and npr-1(null) mutants do not aggregate without food. To ask whether all food sources induce social behaviour, we grew npr-1 mutants on a variety of soil bacteria. When grown on NGM, all bacteria tested induce aggregation. Surprisingly however, if bacteria are grown on simple carbon sources aggregation is strongly suppressed, regardless of the bacterial strain tested. To gain insights into the neuronal circuitry regulating aggregation we looked for mutations that abolish social behaviour. Mutations in ocr-2 and osm-9 , genes that encode subunits of a capsaicin receptor-like channel, completely abolish social behaviour. OCR-2 and OSM-9 are co-expressed in 6 pairs of neurons. We expressed the OCR-2 subunit in each of these neurons in an ocr-2; npr-1 background. We find that expression of OCR-2 in ASH or ADL, but not other neurons, is sufficient to restore social behaviour. Two other genes that suppress social behavior are odr-4 and odr-8 . odr-4 encodes a novel transmembrane protein required for localizing odorant receptors to the cilia of sensory neurons. Expression of ODR-4 in ADL, but not in any other neuron tested, restores social behaviour to odr-4; npr-1 animals. The ADL and ASH neurons have been shown to mediate avoidance behaviour. Their involvement suggests that a repulsive cue plays a role in social behaviour, and the requirement for odr-4 suggests that a G protein-coupled receptor senses this cue. The carbon source experiments suggest that the bacterial food itself is a source of a repulsive cue. A role for repulsive cues in social behaviour was originally suggested by Davis and Avery (WBG 11(5): 69). E. coli is also a source of attractive cues, particularly water-soluble cues, which may also impinge on the social response. Together these results suggest that social behaviour is induced partly in response to aversive stimuli sensed by ADL and ASH.

Mario de Bono et al. (2002) European Worm Meeting "Antagonistic signalling pathways in neurons exposed to the body fluid regulate social feeding in C. elegans"

Mario De Bono, Juliet Coates

[European Worm Meeting, 2002]

Wild isolates of C. elegans can feed either alone or in groups. This natural variation in behaviour is associated with a single residue difference in NPR-1, a predicted neuropeptide receptor related to NPY receptors. NPR-1 suppresses social feeding, since null mutations in npr-1 make wild solitary feeders social feeders. A functional NPR-1::GFP fusion protein under the control of the npr-1 promoter is expressed in about 20 neuron types. To identify the neurons where NPR-1 acts to suppress social feeding we expressed NPR-1::GFP in subsets of these neurons using heterologous promoters. Expression of the NPR-1 isoform associated with solitary feeding in the neurons AQR, PQR and URX is sufficient to suppress social feeding. Targetted expression of an activated K+ channel in the same neurons also suppresses social feeding. AQR, PQR and URX are unusual neurons in C. elegans, being in direct contact with the body fluid of the animal. NPR-1 activity in these neurons may suppress social feeding by antagonising signalling through a cGMP-gated ion channel encoded by tax-2 and tax-4. Mutations in tax-2 or tax-4 disrupt social feeding, and tax-4 is required in several neurons for social feeding, including one or more of AQR, PQR and URX. One possibility is that NPR-1 antagonises cGMP ion channel activity in AQR, PQR, and URX by hyperpolarizing these neurons. Such an inhibitory role of npr-1 would be analogous to the activity of mammalian NPY receptors, that hyperpolarise hippocampal neurons, and proopiomelanocortin-containing anorexigenic neurons in the hypothalamus. Our data suggest a model in which the AQR, PQR and URX neurons integrate antagonistic signals in the body fluid to regulate social versus solitary feeding.

Sokolowski MB (2002) Nature "Neurobiology: social eating for stress."

Sokolowski MB

[Nature, 2002]

Behavioral ecologists have shown that many animals form social groups in conditions. Neurobiological evidence for this behaviour has now been discovered in the nematode worm, Caenorhabditis elegans. On pages 899 and 925 of this issue, de Bono et al. and Coates and de Bono present striking results on the genetic, molecular and neural mechanisms underlying nematode social feeding. These discoveries provide tantalizing insights into the effects of stress in social groupings.

Mitchell A (1998) Nature "Behavioural genetics. Worming out social secrets."

Mitchell A

[Nature, 1998]

Some species of the nematode worm (Caenorhabditis elegans) are sociable diners, clumping together to share a meal, yet others are more solitary. Why? According to a report by de Bono and Bargmann, these differences can be explained by a change of just one amino acid in a putative neuropeptide receptor.

Valperga, Giulio et al. (2021) International Worm Meeting "Experience-dependent gene expression changes across a defined neural circuit in C. elegans"

de Bono, Mario, Beets, Isabel, Valperga, Giulio

[International Worm Meeting, 2021]

Neurons adapt to sensory experience through mechanisms that couple neural activity to gene expression changes. To what extent this mechanism alters behavioral programs, and how activity-dependent changes are coordinated across a neural circuit, is unclear. In C. elegans prolonged exposure to low oxygen (O2) levels reprograms O2-escape behavior, sculpts responses to other sensory cues and alters stimulus-evoked Ca2+ responses. To characterize the molecular changes that underpin this plasticity, we use cell-type-specific RNA sequencing to profile separate components of the O2-circuit in animals grown at either high (21%) or low (7%) O2. In each profiled component, we identify hundreds of experience-regulated genes, including neuropeptides, neuropeptide receptors, transcription factors and gap junctions. We show that experience-dependent regulation of these genes is contingent on O2-evoked activity within the O2-circuit. Across the circuit, transcriptional programs initiated by low O2 are mostly different between O2-sensing neurons and downstream interneurons. Despite these differences, we identify a large number of neuropeptide genes that show activity-regulated gene expression in both neural classes including short uncharacterised peptides which are likely to be secreted. Blocking peptidergic signalling from the RMG interneurons prevents animals to fully reprogram their O2-escape behavior. By comparison, blocking synaptic communication or peptidergic signalling in O2-sensing neurons has relatively little effect on the experience-dependent plasticity of O2-responses. These findings suggest a model where information about O2 experience is broadcasted from interneurons using neuropeptides to reprogram downstream circuits and behavior. This mechanism could help shed light on how activity-dependent changes are coordinated across neural circuits.

Laurent, Patrick et al. (2009) International Worm Meeting "Complex properties of C. elegans oxygen sensing neurons shape different behavioural responses to oxygen."

Murphy, Robin, Busch, Karl Emanuel, de Bono, Mario, Laurent, Patrick

[International Worm Meeting, 2009]

Aggregating wild C. elegans mount complex behavioural responses to ambient oxygen. These include responses to increases as well as decreases in oxygen, transient responses coupled to d[O2]/dt, persistent behavioural changes coupled to [O2] and changes in tuning of the responses depending on experience, context, or genetic background. Here we combine calcium imaging and mutant studies to link these varied behavioural features to different properties of oxygen sensing neurons. We show that some oxygen-sensing neurons exhibit biphasic calcium responses to a rise in O2. These consist of transient spike of high calcium when O2 levels rise followed by a plateau of elevated calcium. The plateaux are apparently coupled to [O2] and can last > 30 minutes - as long as [O2] remains high. This perduring signaling implies different states for the nervous system of animals kept at different oxygen tensions. Consistent with this, feeding animals kept in 21% O2 continue roaming while [O2] remains high (> 30 minutes) and remain in a dwelling state while oxygen is at 7% (> 30 minutes). In wild aggregating strains tuning of both behavioural and neural responses involve multiple oxygen sensors including soluble guanylate cyclases and a novel neural globin, glb-5, which can bind O2 itself. GLB-5 appears to act antagonistically to the soluble guanylate cylcases GCY-35 and 36 to tune the responses to a narrow range of oxygen close to 21% (1,2,3). Both behavioural and neural responses to O2 can be reprogrammed by experience. When cultivated in 7% oxygen, N2 animals shift the dynamic range of their responses towards lower [O2]. Similarly, the dynamic range of calcium responses in oxygen sensing neurons is shifted to lower [O2]. Interestingly, in strains that bear the glb-5 allele found in aggregating wild strains, this plasticity is substantially reduced. In this way these animals maintain tuning close to 21% oxygen - the O2 tension found at earth''s surface - irrespective of experience. We speculate that this tuning constancy may allow C. elegans to recognize the surface. Antagonistically acting sensors may represent a general mechanism to achieve tuning constancy in cases where this is important, such as when monitoring physiological parameters with narrow bounding limits such as [O2], and pH. 1) Soluble guanylate cyclases act in neurons exposed to the body fluid to promote C. elegans aggregation behavior. Cheung BH, Arellano-Carbajal F, Rybicki I, de Bono M. Curr Biol. 2004 Jun 22;14(12):1105-11. 2) Oxygen sensation and social feeding mediated by a C. elegans guanylate cyclase homologue. Gray JM, Karow DS, Lu H, Chang AJ, Chang JS, Ellis RE, Marletta MA, Bargmann CI. Nature. 2004 Jul 15;430 317-22.

Soltesz, Z. et al. (2011) International Worm Meeting "Carbon dioxide avoidance is mediated by a diverse set of sensory neurons in C. elegans."

Soltesz, Z., de Bono, M., Bretscher, A. J.

[International Worm Meeting, 2011]

Monitoring carbon dioxide levels has a twofold importance for many living organisms: CO2 can act as a sensory cue for food or other animals, while regulating internal CO2 levels is an important part of homeostasis. C. elegans relies on diffusion for gas exchange, and avoids CO2 levels as low as 1%. We are interested in the neural and molecular mechanisms underlying the C. elegans CO2 avoidance behaviour. Mutants defective in the tax-4 or tax-2 genes, which encode the a and b subunits, respectively, of a cGMP-gated ion channel, showed reduced CO2 avoidance in behavioural assays1,2. By expressing tax-2 cDNA from neuron-specific promoters in tax-2 mutants to rescue the avoidance behaviour, and by imaging neurons using the genetically encoded calcium indicator YC3.60, we have shown that sensory neurons previously implicated in oxygen, temperature, and salt-sensing, including BAG, AFD and ASE, are CO2 sensors as well3. We have observed both persistent and transient cell-intrinsic calcium-responses in several sensory neurons, suggesting that CO2 stimuli could modulate neural activity in C. elegans in a complex manner. We are therefore investigating how CO2 stimuli can affect neural processing in downstream neurons. 1 Andrew Jonathan Bretscher, Karl Emanuel Busch, and Mario de Bono, A carbon dioxide avoidance behavior is integrated with responses to ambient oxygen and food in Caenorhabditis elegans. PNAS 105(23):8044-8049 2 Elissa A. Hallem and Paul W. Sternberg, Acute carbon dioxide avoidance in Caenorhabditis elegans. PNAS 105(23):8038-8043 3 Andrew Jonathan Bretscher, Eiji Kodama-Namba, Karl Emanuel Busch, Robin Joseph Murphy, Zoltan Soltesz, Patrick Laurent and Mario de Bono, Temperature, Oxygen, and Salt-Sensing Neurons in C. elegans Are Carbon Dioxide Sensors that Control Avoidance Behavior. Neuron 69(6):1099-1113.

De Bono M et al. (1998) Cell "Natural variation in a neuropeptide Y receptor homolog modifies social behavior and food response in C. elegans."

Bargmann CI, De Bono M

[Cell, 1998]

Natural isolates of C. elegans exhibit either solitary or social feeding behavior. Solitary foragers move slowly on a bacterial lawn and disperse across it, while social foragers move rapidly on bacteria and aggregate together. A loss-of-function mutation in the npr-1 gene, which encodes a predicted G protein-coupled receptor similar to neuropeptide Y receptors, causes a solitary strain to take on social behavior. Two isoforms of NPR-1 that differ at a single residue occur in the wild. One isoform, NPR-1 215F, is found exclusively in social strains, while the other isoform, NPR-1 215V, is found exclusively in solitary strains. An NPR-1 215V transgene can induce solitary feeding behavior in a wild social strain. Thus, isoforms of a putative neuropeptide receptor generate natural variation in C. elegans feeding behavior.AD - Howard Hughes Medical Institute, Department of Anatomy, The University of California, San Francisco 94143-0452, USA.FAU - de Bono, MAU - de Bono MFAU - Bargmann, C IAU - Bargmann CILA - engSI - GENBANK/U49944PT - Journal ArticleCY - UNITED STATESTA - CellJID - 0413066RN - 0 (Helminth Proteins)RN - 0 (Receptors, Neuropeptide Y)RN - EC 3.6.1.- (GTP-Binding Proteins)SB - IM