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Lee HK, Lee TY, Lee JI, Park KS, Yoon KH. Precise sensorimotor control impacts reproductive fitness of C. elegans in 3D environments. Neuroreport 2024; 35:123-128. [PMID: 38109381 PMCID: PMC10766090 DOI: 10.1097/wnr.0000000000001986] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2023] [Accepted: 11/28/2023] [Indexed: 12/20/2023]
Abstract
The ability of animals to sense and navigate towards relevant cues in complex and elaborate habitats is paramount for their survival and reproductive success. The nematode Caenorhabditis elegans uses a simple and elegant sensorimotor program to track odors in its environments. Whether this allows the worm to effectively navigate a complex environment and increase its evolutionary success has not been tested yet. We designed an assay to test whether C. elegans can track odors in a complex 3D environment. We then used a previously established 3D cultivation system to test whether defect in tracking odors to find food in a complex environment affected their brood size. We found that wild-type worms can accurately migrate toward a variety of odors in 3D. However, mutants of the muscarinic acetylcholine receptor GAR-3 which have a sensorimotor integration defect that results in a subtle navigational defect steering towards attractive odors, display decreased chemotaxis to the odor butanone not seen in the traditional 2D assay. We also show that the decreased ability to locate appetitive stimuli in 3D leads to reduced brood size not observed in the standard 2D culture conditions. Our study shows that mutations in genes previously overlooked in 2D conditions can have a significant impact in the natural habitat, and highlights the importance of considering the evolutionary selective pressures that have shaped the behavior, as well as the underlying genes and neural circuits.
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Affiliation(s)
- Hee Kyung Lee
- Department of Physiology, Yonsei University Wonju College of Medicine
- Mitohormesis Research Center, Yonsei University Wonju College of Medicine
- Department of Global Medical Science, Yonsei University Wonju College of Medicine
| | - Tong Young Lee
- Division of Biological Science and Technology, College of Science and Technology, Yonsei University, Mirae Campus, Wonju, South Korea
| | - Jin I. Lee
- Division of Biological Science and Technology, College of Science and Technology, Yonsei University, Mirae Campus, Wonju, South Korea
| | - Kyu-Sang Park
- Department of Physiology, Yonsei University Wonju College of Medicine
- Mitohormesis Research Center, Yonsei University Wonju College of Medicine
- Department of Global Medical Science, Yonsei University Wonju College of Medicine
| | - Kyoung-hye Yoon
- Mitohormesis Research Center, Yonsei University Wonju College of Medicine
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2
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Oliver D, Ramachandran S, Philbrook A, Lambert CM, Nguyen KCQ, Hall DH, Francis MM. Kinesin-3 mediated axonal delivery of presynaptic neurexin stabilizes dendritic spines and postsynaptic components. PLoS Genet 2022; 18:e1010016. [PMID: 35089924 PMCID: PMC8827443 DOI: 10.1371/journal.pgen.1010016] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Revised: 02/09/2022] [Accepted: 01/03/2022] [Indexed: 12/02/2022] Open
Abstract
The functional properties of neural circuits are defined by the patterns of synaptic connections between their partnering neurons, but the mechanisms that stabilize circuit connectivity are poorly understood. We systemically examined this question at synapses onto newly characterized dendritic spines of C. elegans GABAergic motor neurons. We show that the presynaptic adhesion protein neurexin/NRX-1 is required for stabilization of postsynaptic structure. We find that early postsynaptic developmental events proceed without a strict requirement for synaptic activity and are not disrupted by deletion of neurexin/nrx-1. However, in the absence of presynaptic NRX-1, dendritic spines and receptor clusters become destabilized and collapse prior to adulthood. We demonstrate that NRX-1 delivery to presynaptic terminals is dependent on kinesin-3/UNC-104 and show that ongoing UNC-104 function is required for postsynaptic maintenance in mature animals. By defining the dynamics and temporal order of synapse formation and maintenance events in vivo, we describe a mechanism for stabilizing mature circuit connectivity through neurexin-based adhesion.
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Affiliation(s)
- Devyn Oliver
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, Massachusetts, United States of America
| | - Shankar Ramachandran
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, Massachusetts, United States of America
| | - Alison Philbrook
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, Massachusetts, United States of America
| | - Christopher M. Lambert
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, Massachusetts, United States of America
| | - Ken C. Q. Nguyen
- Department of Neuroscience, Albert Einstein College of Medicine, New York, New York, United States of America
| | - David H. Hall
- Department of Neuroscience, Albert Einstein College of Medicine, New York, New York, United States of America
| | - Michael M. Francis
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, Massachusetts, United States of America
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Ramachandran S, Banerjee N, Bhattacharya R, Lemons ML, Florman J, Lambert CM, Touroutine D, Alexander K, Schoofs L, Alkema MJ, Beets I, Francis MM. A conserved neuropeptide system links head and body motor circuits to enable adaptive behavior. eLife 2021; 10:71747. [PMID: 34766905 PMCID: PMC8626090 DOI: 10.7554/elife.71747] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2021] [Accepted: 11/11/2021] [Indexed: 01/11/2023] Open
Abstract
Neuromodulators promote adaptive behaviors that are often complex and involve concerted activity changes across circuits that are often not physically connected. It is not well understood how neuromodulatory systems accomplish these tasks. Here, we show that the Caenorhabditis elegans NLP-12 neuropeptide system shapes responses to food availability by modulating the activity of head and body wall motor neurons through alternate G-protein coupled receptor (GPCR) targets, CKR-1 and CKR-2. We show ckr-2 deletion reduces body bend depth during movement under basal conditions. We demonstrate CKR-1 is a functional NLP-12 receptor and define its expression in the nervous system. In contrast to basal locomotion, biased CKR-1 GPCR stimulation of head motor neurons promotes turning during local searching. Deletion of ckr-1 reduces head neuron activity and diminishes turning while specific ckr-1 overexpression or head neuron activation promote turning. Thus, our studies suggest locomotor responses to changing food availability are regulated through conditional NLP-12 stimulation of head or body wall motor circuits.
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Affiliation(s)
- Shankar Ramachandran
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, United States
| | - Navonil Banerjee
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, United States
| | - Raja Bhattacharya
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, United States
| | - Michele L Lemons
- Department of Biological and Physical Sciences, Assumption University, Worcester, United States
| | - Jeremy Florman
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, United States
| | - Christopher M Lambert
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, United States
| | - Denis Touroutine
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, United States
| | - Kellianne Alexander
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, United States
| | - Liliane Schoofs
- Department of Biology, University of Leuven (KU Leuven), Leuven, Belgium
| | - Mark J Alkema
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, United States
| | - Isabel Beets
- Department of Biology, University of Leuven (KU Leuven), Leuven, Belgium
| | - Michael M Francis
- Department of Neurobiology, University of Massachusetts Chan Medical School, Worcester, United States
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Abstract
Following the spectacular success of molecular genetics in deciphering the genetic code in the 1960s, several of its leading practitioners felt sufficiently emboldened to use their newly acquired skills to move on and study that most enigmatic of biological organs - the brain. Sydney Brenner's approach was to focus on Caenorhabditis elegans, a nematode that is genetically tractable, has a nervous system that generates a rich repertoire of behaviours yet is small enough to allow anatomical reconstructions with ultrastructural precision. Through force of personality and some inspired pioneering studies, Brenner managed to ignite a bonfire of enthusiasm for this organism, which has resulted in its nervous system becoming the best understood of that in any organism. Initially, many were skeptical that this rather strange structure with just a few hundred neurons would yield insights that were relevant to vertebrate nervous systems. However, fifty years on we know that the basic repertoire of molecular components of worm and human nervous systems are remarkably similar. Furthermore, worms have a similar diversity of these components rather than a primitive sub-set. It appears that the fundamental difference in a vertebrate nervous system is a huge expansion of the neural units that comprise a basic brain such as that exemplified in C. elegans.
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Affiliation(s)
- John White
- Laboratory of Cell and Molecular Biology, University of Wisconsin, Madison, WI, USA
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Structural and developmental principles of neuropil assembly in C. elegans. Nature 2021; 591:99-104. [PMID: 33627875 PMCID: PMC8385650 DOI: 10.1038/s41586-020-03169-5] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2020] [Accepted: 11/12/2020] [Indexed: 01/31/2023]
Abstract
Neuropil is a fundamental form of tissue organization within the brain1, in which densely packed neurons synaptically interconnect into precise circuit architecture2,3. However, the structural and developmental principles that govern this nanoscale precision remain largely unknown4,5. Here we use an iterative data coarse-graining algorithm termed 'diffusion condensation'6 to identify nested circuit structures within the Caenorhabditis elegans neuropil, which is known as the nerve ring. We show that the nerve ring neuropil is largely organized into four strata that are composed of related behavioural circuits. The stratified architecture of the neuropil is a geometrical representation of the functional segregation of sensory information and motor outputs, with specific sensory organs and muscle quadrants mapping onto particular neuropil strata. We identify groups of neurons with unique morphologies that integrate information across strata and that create neural structures that cage the strata within the nerve ring. We use high resolution light-sheet microscopy7,8 coupled with lineage-tracing and cell-tracking algorithms9,10 to resolve the developmental sequence and reveal principles of cell position, migration and outgrowth that guide stratified neuropil organization. Our results uncover conserved structural design principles that underlie the architecture and function of the nerve ring neuropil, and reveal a temporal progression of outgrowth-based on pioneer neurons-that guides the hierarchical development of the layered neuropil. Our findings provide a systematic blueprint for using structural and developmental approaches to understand neuropil organization within the brain.
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Wright EAP, Goltsev AV. Statistical analysis of unidirectional and reciprocal chemical connections in the C. elegans connectome. Eur J Neurosci 2020; 52:4525-4535. [PMID: 33022789 DOI: 10.1111/ejn.14988] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2020] [Revised: 09/14/2020] [Accepted: 09/15/2020] [Indexed: 11/29/2022]
Abstract
We analyze unidirectional and reciprocally connected pairs of neurons in the chemical connectomes of the male and hermaphrodite Caenorhabditis elegans, using recently published data. Our analysis reveals that reciprocal connections provide communication between most neurons with chemical synapses, and comprise on average more synapses than both unidirectional connections and the entire connectome. We further reveal that the C. elegans connectome is wired so that afferent connections onto neurons with large numbers of presynaptic neighbors (in-degree) comprise an above-average number of synapses (synaptic multiplicity). Notably, the larger the in-degree of a neuron the larger the synaptic multiplicity of its afferent connections. Finally, we show that the male forms two times fewer reciprocal connections between sex-shared neurons than the hermaphrodite, but a large number of reciprocal connections with male-specific neurons. These observations provide evidence for Hebbian structural plasticity in the C. elegans.
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Affiliation(s)
- Edgar A P Wright
- Department of Physics & I3N, University of Aveiro, Aveiro, Portugal
| | - Alexander V Goltsev
- Department of Physics & I3N, University of Aveiro, Aveiro, Portugal.,A.F. Ioffe Physico-Technical Institute, St. Petersburg, Russia
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Larson SD, Gleeson P, Brown AEX. Connectome to behaviour: modelling Caenorhabditis elegans at cellular resolution. Philos Trans R Soc Lond B Biol Sci 2018; 373:20170366. [PMID: 30201832 PMCID: PMC6158229 DOI: 10.1098/rstb.2017.0366] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/17/2018] [Indexed: 12/20/2022] Open
Abstract
It has been 30 years since the 'mind of the worm' was published in Philosophical Transactions B (White et al 1986 Phil. Trans. R. Soc. Lond. B314, 1-340). Predicting Caenorhabditis elegans' behaviour from its wiring diagram has been an enduring challenge since then. This special theme issue of Philosophical Transactions B combines research from neuroscientists, physicists, mathematicians and engineers to discuss advances in neural activity imaging, behaviour quantification and multiscale simulations, and how they are bringing the goal of whole-animal modelling at cellular resolution within reach.This article is part of a discussion meeting issue 'Connectome to behaviour: modelling C. elegans at cellular resolution'.
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Affiliation(s)
| | - Padraig Gleeson
- OpenWorm Foundation, Boston, MA, USA
- Department of Neuroscience, Physiology and Pharmacology, University College London WC1E 6BT, UK
| | - André E X Brown
- MRC London Institute of Medical Sciences, London W12 0N, UK
- Institute of Clinical Sciences, Imperial College London, London SW7 2AZ, UK
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