Watteyne, Jan et al. (2021) International Worm Meeting "Untying the Gordian Knot: unravelling spatiotemporal activity in the C. elegans neuropeptide-receptor network"

Cho, Sumin, Vertes, Petra E., Schafer, William R., Ripoll-Sanchez, Lidia, Vandewyer, Elke, Watteyne, Jan, Beets, Isabel

[International Worm Meeting, 2021]

Neuropeptides are important modulators of organismal physiology and behavior. Yet, the rules and constraints by which these modulatory substances achieve both local and widespread physiological effects remain poorly understood. Currently lacking is a comprehensive analysis of the neuropeptide signaling network at an organismal systems level. The C. elegans genome shows a broad diversity of neuropeptide pathways, harboring around 150 genes encoding neuropeptides and a similar number of peptide GPCRs. Using reverse pharmacology, we have systematically mapped the biochemical network of neuropeptide-receptor interactions in the C. elegans nervous system. By screening for neuropeptide-GPCR couples, we identified receptors for all C. elegans RFamide-like peptides (FLPs) and many neuropeptide-like proteins (NLPs). These peptidergic pathways are organized into a dense signaling network including promiscuous neuropeptides and receptors. To further understand the functional organization of peptidergic circuits, we have adopted genetically-encoded sensors for neuropeptide-receptor activation that allow characterizing the spatiotemporal activity patterns of neuromodulatory signaling axes in the network. Using optogenetics, we found that conditional signaling of CAPA-1 neuropeptides, through activation of the neuromedin U receptor NMUR-1, underpins experience-dependent plasticity of salt chemotaxis behavior in C. elegans. CAPA-1 signaling from ASG neurons is specifically required for the retrieval, but not the acquisition, of learned salt avoidance. This highlights temporal aspects of neuropeptide signaling as important organizational motifs within the neuropeptide network, which we are further addressing with activity readouts of neuropeptide-receptor signaling. These findings and tools act as a scaffold to investigate how flexible behaviors emerge from neuromodulatory networks.

Rafi, Ibnul et al. (2019) International Worm Meeting "The neuropeptidergic connectome of Caenorhabditis elegans."

Temmerman, Liesbet, Vertes, Petra, Hobert, Oliver, YANG, Xinyi, Vandewyer, Elke, Schafer, William, Beets, Isabel, Sanchez, Lidia, Chen, Chi, Rafi, Ibnul, Bael, Sven

[International Worm Meeting, 2019]

A "connectome" describes the complete synaptic wiring diagram of a brain. Past and current connectomic efforts are focused on determining the anatomical, i.e. chemical and electrical synaptic connections between neurons in a brain, thereby completely ignoring aspects of neuronal communication that are likely of equal importance but are not captured by anatomical connections: Neuromodulatory communication by neuropeptides and their cognate receptors. Neuropeptidergic communication is usually non-synaptic, i.e. neuropeptides are often released from non-synaptic sites and cognate neuropeptide receptors are often located distal from the source of the cognate neuropeptide. While the importance of a number of neuropeptides and their receptors in controlling behavior are well appreciated, the extent of usage of neuropeptidergic signaling is only beginning to be fully appreciated. Every neuron in an animal nervous system is now thought to express at least one neuropeptide, but the pathways of communication of these neuropeptidergic signals have not been comprehensibly mapped and, hence, our understanding of information flow in the nervous system remains incomplete. A consortium of four laboratories (Hobert, Schafer, Beets, Temmerman Labs) has received NIH funds to establish the first comprehensive neuropeptidergic connectome. We build such a connectome through (1) comprehensively defining ligand/receptor pairs through in vitro receptor activation assays, (2) defining the expression patterns of all neuropeptide and neuropeptide receptor encoding genes, (3) synthesizing these data into a neuropeptidergic network and computationally comparing the topology of this network to the synaptic connectivity network and (4) undertaking a preliminary functional validation of specific nodes and edges of this network. Comparing a neuropeptidergic connectome to that of the completely established synaptic connectome, we expect to describe a "multilayer connectome" with substantially distinct pathways of information flow, as well as distinct and similar topological features.

Ripoll-Sanchez, Lidia et al. (2021) International Worm Meeting "Mapping the neuropeptidergic connectome of Caenorhabditis elegans"

Ripoll-Sanchez, Lidia, Hammarlund, Marc, Weinreb, Alexis, Miller III, David M., Beets, Isabel, Watteyne, Jan, Taylor, Seth R., Schafer, William R., Vertes, Petra E., Hobert, Oliver

[International Worm Meeting, 2021]

The synaptically-wired neuronal circuitry is modulated by monoamines and neuropeptides, which act mostly through extrasynaptic volume transmission. This modulation is critical to nervous system function, yet little is known about the structure and function of extrasynaptic signaling networks at a whole-organism level. To this end, we used the recently published single neuron gene expression from the CeNGEN database along with deorphanization data for neuropeptide-activated G-protein coupled receptors (GPCRs) (see Jan Watteyne et al. abstract for this meeting) to generate a draft connectome of neuropeptide signaling networks in C. elegans. We based our network on single-cell neuronal expression patterns of 93 neuropeptide-receptor couples. In our baseline network edges were formed when the sending neuron expressed a given neuropeptide, the receiving neuron expressed the cognate receptor, and both neurons extended overlapping processes in the same neuropil. We also generated an unrestricted network with no spatial restriction on edge formation which allowed for potential long-range signaling. Since all 302 neurons of the adult hermaphrodite express at least one neuropeptide precursor gene and nearly all express at least one neuropeptide GPCR, both the baseline (with 31866 edges) and the unrestricted (with 54267 edges) neuropeptide networks were extremely dense compared to the synaptic connectome (with 2284 edges). In addition to its high density, the neuropeptide connectome differs in significant ways from the synaptic and monoamine signaling networks. For example, whereas the synaptic network consists of a small (11 neurons) core of high-degree hubs and a low-degree periphery, the neuropeptides network is more decentralised with a great number (103 neurons) of very high-degree nodes that form an interconnected rich club. Moreover, in contrast to the monoamine network, which shows very low reciprocity, the neuropeptide connectome shows higher than expected reciprocity, even though the networks formed by individual ligand-receptor couples are not. Finally, although the premotor neurons of the synaptic rich club have high neuropeptide degree, several of the most important nodes in the neuropeptide network are little-studied neurons that may be specialised for peptidergic neuromodulation. In the future, functional studies of these neurons and their role in behaviour may provide new insight into the control of behavioral states.

Martin Gutternigg et al. (2006) European Worm Meeting "Glycosidases of Caenorhabditis elegans involved in N-glycan processing"

Martin Gutternigg, Matthias Hackl, Ute Stemmer, Iain B. H. Wilson, Petra Geier, Gunter Lochnit, Ramona Ranftl, Katharina Paschinger, Verena Jantsch, Dorothea Lubich

[European Worm Meeting, 2006]

Martin Gutternigg, Dorothea Lubich, Matthias Hackl, Katharina Paschinger, Ute Stemmer, Verena Jantsch1, Gnter Lochnit2, Ramona Ranftl, Petra Geier and Iain B. H. Wilson. Recent data indicates that in addition to the Golgi ?-mannosidases, the model nematode Caenorhabditis elegans also possesses, like insects, an N-acetylhexosaminidase activity putatively involved in N-glycan processing in the Golgi. The presence of such an activity is invoked, not just on the basis of the detected enzyme activity, but also to explain the absence of terminal N-acetylglucosamine residues on structures which require the prior action of N-acetylglucosaminyltransferase I during their biosynthesis. In order to understand the genetic basis for these activities, we have cloned cDNAs encoding members of both glycohydrolase families 20 and 38 from the worm. The encoded glycosidases were expressed in the yeast Pichia pastoris as soluble forms lacking putative cytoplasmic and transmembrane domains. Four glycohydrolase family 20 members were shown to cleave p-nitrophenyl-?-N-acetylglucosaminide and/or p-nitrophenyl-?-N-acetylgalactosaminide, but showed contrasting specificities with regard to N-glycan substrates. On the other hand, one glycohydrolase family 38 member was shown to be active using p-nitrophenyl-?-mannoside as a substrate and, in addition, had mannosidase II activity. Analysis of the glycans of the relevant mutant showed large-scale changes in the N-glycosylation spectrum. These, therefore, are the first data on the activity of Caenorhabditis glycosidases towards N-glycan substrates and should aid the further elucidation of N-glycan processing in this organism.