Hendricks, Michael et al. (2011) International Worm Meeting "Multiplex sensorimotor encoding in RIA interneurons."

Maffey, Nicolas, Ha, Heon-Ick, Hendricks, Michael, Zhang, Yun

[International Worm Meeting, 2011]

The C. elegans nervous system is a compact, highly interconnected network with considerable overlap between circuits mediating different sensorimotor behaviors. Describing how neurons integrate signals at the physiological level is necessary for understanding neural circuit function and for constructing biologically relevant models of network dynamics. We therefore chose to investigate the physiological properties of the RIA interneuron, which receives convergent polymodal inputs from sensory networks and has reciprocal contacts with motor neurons. Furthermore, RIA is required for experience-dependent modulation of several complex behaviors, suggesting that it is a key component of these networks. Here, we show that RIA simultaneously encodes sensory input and motor activity through physiological partitioning of its single axonal process. Compartmentalized calcium signals in the axon spatially encode motor behavior; simultaneously, sensory inputs are temporally encoded by synchronous calcium transients throughout the axon. We used mutants in specific transmitter systems and transgenic silencing of transmitter release in RIA's synaptic partners to dissect the circuit elements that drive these dynamics. Compartmentalization of the RIA axon and motor mapping require cholinergic input from motor systems, while both glutamatergic and cholinergic transmission are required for normal sensory-evoked responses. Therefore, we propose that RIA modulates locomotory behaviors by integrating motor dynamics with sensory input on a subcellular scale. Our results suggest that information flow in neural circuits can be multiplexed, with individual neurons receiving and distributing signals of different types and modalities via distinct compartments and encoding mechanisms. This provides a physiological basis for understanding sensorimotor integration at the single neuron level and suggests an intriguing new layer of network complexity within the C. elegans nervous system.

Hendricks, Michael et al. (2013) International Worm Meeting "Sensory responses to graded stimuli: a role in bidirectional chemotaxis?"

Samuel, Aravi, Linjiao, Luo, Hendricks, Michael, Zhang, Yun

[International Worm Meeting, 2013]

C. elegans can migrate up or down salt gradients toward a remembered cultivation concentration. Both positive and negative chemotaxis are driven by biased random walks of opposite sign, and the chloride-sensing neuron ASER is required for chemotaxis in both directions. We are interested in how the same neural circuit can mediate opposite behaviors. Responses of ASER, measured with genetically-encoded calcium indicators, have been previously examined in response to large, abrupt step changes in salt concentration. However, during chemotaxis assays, crawling animals experience smooth changes in salt concentration. To better match behavioral conditions, we exposed semi-restrained worms to quasi-linear graded changes in salt concentration that match what is experienced by animals migrating on plates (~50 mM/s). ASER shows sustained activity in response to decreasing salt gradients, however the temporal dynamics of these responses differ depending on whether the animals are being tested above or below their cultivation concentration. ASER exhibits activity during increases in salt concentration only above its cultivation concentration. Thus, ASER responses can represent both the direction of the temporal salt gradient and whether it is "toward" or "away" from a remembered set point. We hypothesize that downstream interneurons differentially integrate or respond to the various activity patterns in ASER.

Ouellette, Marie-Helene et al. (2021) International Worm Meeting "Neurogenetics of modulatory cholinergic signaling in C. elegans interneurons"

Hendricks, Michael, Ouellette, Marie-Helene

[International Worm Meeting, 2021]

We previously identified a small circuit that integrates both sensory and motor input, involving a glutamatergic interneuron (RIA) that receives cholinergic feedback from head motor neurons (SMDs). RIA is functionally and spatially subdivided into compartments corresponding to sensory input and reciprocal motor domains. Motor input, which is mediated specifically through GAR-3 mAChRs, is received in phase with head movement during locomotion, leading to compartmentalized local calcium events and gait regulation. We found that a novel phenotype we named "head lifting" (movement of the worm's anterior section along the Z axis) appears to strongly correlate with disruption of RIA compartmentalization. Head lifting arises from bilateral (DV) activation of head muscles and occurs preferentially at particular points in the locomotion cycle. Here, we characterize this phenotype and use it to probe the genetics of compartmentalized signals in RIA.

Guisnet, Aurelie et al. (2021) International Worm Meeting "A deep learning approach to calcium imaging analysis"

Rivest, Maxime, Guisnet, Aurelie, Hendricks, Michael

[International Worm Meeting, 2021]

Analysis of calcium imaging recordings is tedious, repetitive and time consuming. In this new project, we propose to develop a machine learning-based automated tool for the analysis of recordings from C. elegans neurons, thereby reducing noise, time loss and experimenter bias. We are specifically training our model to segment time-lapse fluorescence recordings of the RIA interneuron in semi-restrained animals. Our tool can segment animals and track their head movements as well as identify the three compartments of the RIA neurite. This prototype tool demonstrates the potential of deep learning to accelerate and improve data acquisition from time-lapse fluorescence recordings and other imaging data.

Pradhan, Sreeparna et al. (2019) International Worm Meeting "Environmental programming of adult foraging behavior."

Hendricks, Michael, Quilez, Sabrina Rita, Homer, Kai, Pradhan, Sreeparna

[International Worm Meeting, 2019]

Animals tune their foraging strategies by using past experience to estimate current resource availability and distribution. Previous studies have reported plasticity in foraging strategies in C. elegans over short time scales over a few hours in response to environmental fluctuations. Genetic variation between different wild isolates are also known to affect foraging decisions, with the lab wild-type N2 strain being the least exploratory and the wild HW CB4856 strain being the most exploratory. We explored whether foraging behavior can be tuned over the time scale of the lifetime of an individual. Stressful environmental conditions like scarcity of food in early larval stages directly affect C. elegans development inducing entry into the dauer developmental arrest phase. We examined adult foraging strategies in post-dauer animals of different genetic backgrounds. Our results show that HW post-dauers have permanently reduced adult foraging behavior, but this long-term plasticity is absent in the lab adapted N2 strain. We also observed changes in the temporal pattern of food search in HW post-dauers, coupled with a high propensity of reversals and turns. We then investigated the neural correlates of this permanent change in behavior, and simultaneously imaged calcium transients in AVA, AIB and RIM which form a local interneuron circuit controlling reversal output. Our results indicate that post-dauer HWs have higher dynamic activity in this circuit in both presence and absence of food cues. We next examined known polymorphisms between the N2 and HW strains to determine the genetic basis of between-strain differences in long-term plasticity. Our work shows that adult foraging behaviour is tuned by developmental experience and involves altering the dynamics of a core navigation circuit, and this plasticity is dependent on the genetic background and life history of the strain.

Tirera, Fouley et al. (2019) International Worm Meeting "Roles of TCN-1 transmembrane protein in C. elegans osmosensation."

Hendricks, Michael, Penalva, Ylauna, Posner, Rachel, Tirera, Fouley, Tse, Victoria

[International Worm Meeting, 2019]

Maintaining a stable intracellular osmolarity is fundamental for the survival of all organisms. Extracellular osmotic changes perturb cellular functions, thus most organisms adopt physiologic and behavioural responses to adapt to and avoid osmotic stress. In mammals, members of the transient receptor potential vanilloid, also known as TRPV channels, are expressed in the osmosensory brain regions, however the underlying molecular mechanisms are not fully understood. In Caenorhabditis elegans, the OSM-9 TRPV channel is expressed in ASH sensory neurons and is involved in high osmolarity avoidance. On contact with a hyperosmotic stimulus, the nematode generates reversals to escape the high osmolarity region. Additionally, a previous study revealed that through RIM interneuron inhibition, food-deprived worms are willing to cross a high osmolarity barrier to reach an attractant, a food odour. Here we investigated the role of the uncharacterized transmembrane protein TCN-1 in osmosensation. We found that tcn-1 mutants display increased sensitivity to hyperosmotic barriers. Unlike wild type animals, food-deprived tcn-1 mutants will not cross a hyperosmotic barrier to reach an attractive odour, despite exhibiting normal locomotion and chemotaxis in the absence of a barrier. Therefore, our study demonstrates the TCN-1 transmembrane protein plays a role in osmosensation and might contribute to the regulation of intracellular osmolarity.

Owens, Hannah et al. (2021) International Worm Meeting "Characterizing the Role of the Mechanosensitive Ion Channel TACAN in C. elegans Osmosensation"

Davidova, Albena, Hendricks, Michael, Owens, Hannah, Tala Tirera, Fouley, Sharif-Naeini, Reza

[International Worm Meeting, 2021]

Mechanotransduction occurs via ion channels whose gating is controlled by mechanical stimuli. Recently, the transmembrane protein TACAN was identified as a mechanosensitive ion channel crucial for sensing mechanical pain in mice, and TACAN homologs were shown to be highly conserved across other species such as humans and nematodes. The nematode C. elegans is an ideal model organism to study the molecular properties of TACAN, given its mapped connectome, simple behavior, and capacity for genetic manipulations. Our preliminary data suggest that the uncharacterized TACAN homolog in C. elegans is involved in worm mechanosensation, specifically contributing to the detection of osmotic stimuli.

Donato, A. et al. (2015) International Worm Meeting "Molecular and cellular mechanisms regulating axonal compartmentalization in C. elegans RIA interneurons."

Ren, J., Donato, A., Zhang, Y., Hilliard, M. A.

[International Worm Meeting, 2015]

Neurons are highly compartmentalized cells consisting of three main structural and functional domains, cell body (soma), axon, and dendrites. In the last decade, increasing experimental evidence has revealed that additional levels of compartmentalization are in place within the processes, providing higher computational potential than previously thought. However, little is known on the molecular and cellular mechanisms that regulate the establishment of these subcellular compartments during development and their maintenance during the lifetime of the animals. A recent study from Yun Zhang's laboratory has shown that the unipolar RIA interneurons display distinct compartmentalized activity in different axonal domains. Remarkably, calcium activity in specific axonal domains is correlated with the direction of the dorsal-ventral head bending and the compartmental activity regulates the amplitude of the head bending (Hendricks et al., 2012). These results reveal the properties and function of RIA axonal compartmentalization. Here, we propose to elucidate the underlying molecular and cellular mechanisms. First, we tested the hypothesis that the functional compartmentalization of RIA results from compartmentalized localization of the muscarinic acetylcholine receptor GAR-3. Previously, it has been shown that the axonal compartmentalized activity of RIA requires the synaptic output of the cholinergic head motor neurons SMDD/V and the function of GAR-3 in RIA (Hendricks et al., 2012). Thus, we analysed the distribution of the GAR-3 receptor in RIA, and found that its localisation is diffused and does not correlate with compartmentalized calcium activity, suggesting different underlying mechanisms. Second, we tested the hypothesis that specific localization of mitochondria in RIA may regulate RIA compartmental activity by buffering calcium waves in certain axonal domains. We found that mitochondria distribution in RIA is not consistent with a potential role in generating calcium compartmentalisation in this cell. Finally, using the GFP reconstruction across synaptic partners (GRASP) (Feinberg et al., 2008), we have specifically labelled the synaptic contacts between SMDs and RIAs, which will allow us to investigate if the calcium compartmentalisation is governed by the precise synaptic organisation in the RIA axon and how changing in the synaptic organisation can affect neuronal activity and therefore the animal behaviour. .

Michael Hoffmann et al. (2006) European Worm Meeting "The Planar Cell Polarity Protein VANG-1 interferes with Intercalation Events during Epithelial Morphogenesis In C. elegans"

Michael Hoffmann, Christoph Segbert, Olaf Bossinger, Gisela Helbig

[European Worm Meeting, 2006]

Michael Hoffmann, Christoph Segbert, Gisela Helbig and Olaf Bossinger. C. elegans VANG-1 is the only homolog of the Drosophila planar cell polarity (PCP) protein Strabismus/Van Gogh. We originally identified VANG-1 as a putative binding partner of DLG-1 (Discs large), a MAGUK protein that acts as a molecular scaffold for the establishment of the apical junction in all epithelia of the C. elegans embryo. The phenotype observed in vang-1 mutant embryos show intercalation defects during epithelial morphogenesis of the intestine and the hypodermis. Similar phenotypes arise in lin-17 (frizzled) mutants or after RNAi against dsh-2 (dishevelled), indicating core components of the PCP pathway in other systems to be involved in cell intercalation in the C. elegans embryo. In addition, VANG-1 and DSH-2 do colocalize and the asymmetric distribution of VANG-1 in epithelia depends on DSH-2. Taken together these results suggests that planar cell polarity might exist in C. elegans.

Miyanishi, Yosuke et al. (2011) International Worm Meeting "Functional imaging of neuronal activity for 2-nonanone stimulation."

Nakai, Junichi, Kimura, Kotaro, Miyanishi, Yosuke

[International Worm Meeting, 2011]

To better understand the neural basis that regulates a worm's sensory behavior and its modulation by learning, we are studying avoidance behavioral responses to 2-nonanone. We previously reported that the avoidance behavior to 2-nonanone is enhanced, rather than reduced, after preexposure to the odor, and this enhancement is acquired as a non-associative dopamine-dependent learning (Kimura et al., J. Neurosci., 2010; Fujita and Kimura, this abstract). In addition, we observed that worms respond to a spatial gradient of 2-nonanone (Yamazoe and Kimura, CE Neuro, 2010), which cannot be simply explained by the pirouette or weathervane strategies. 2-nonanone is mainly sensed by the AWB neurons, which have been shown to exhibit odor-OFF response in aqueous step stimulation with 2-nonanone (Troemel et al., Cell 1997; Ha et al., Neuron 2010). To understand how the neuronal circuits of worms regulate the characteristic 2-nonanone behavioral response, we are monitoring calcium changes in the AWB and downstream neurons using G-CaMP 4 (Shindo et al., PLoS ONE, 2010). We thank Drs. S. Oda, K. Yoshida, and Y. Iino (U. Tokyo) for suggestions on microfluidics; M. Hendricks and Y. Zhang (Harvard) for aqueous 2-nonanone stimulation; and E. Busch and M. de Bono (MRC) for gaseous microfluidic stimulation.