scholarly journals A Neuromechanical Model of Multiple Network Rhythmic Pattern Generators for Forward Locomotion in C. elegans

2021 ◽  
Vol 15 ◽  
Author(s):  
Erick Olivares ◽  
Eduardo J. Izquierdo ◽  
Randall D. Beer
Keyword(s):  
Nerve Cord ◽  
Ventral Nerve Cord ◽  
Stretch Receptor ◽  
Rhythmic Pattern ◽  
Pacemaker Neurons ◽  
C Elegans ◽  
Forward Locomotion ◽  
Pattern Generators ◽  
Multiple Network ◽  
A Chain

Multiple mechanisms contribute to the generation, propagation, and coordination of the rhythmic patterns necessary for locomotion in Caenorhabditis elegans. Current experiments have focused on two possibilities: pacemaker neurons and stretch-receptor feedback. Here, we focus on whether it is possible that a chain of multiple network rhythmic pattern generators in the ventral nerve cord also contribute to locomotion. We use a simulation model to search for parameters of the anatomically constrained ventral nerve cord circuit that, when embodied and situated, can drive forward locomotion on agar, in the absence of pacemaker neurons or stretch-receptor feedback. Systematic exploration of the space of possible solutions reveals that there are multiple configurations that result in locomotion that is consistent with certain aspects of the kinematics of worm locomotion on agar. Analysis of the best solutions reveals that gap junctions between different classes of motorneurons in the ventral nerve cord can play key roles in coordinating the multiple rhythmic pattern generators.

scholarly journals A neuromechanical model of multiple network rhythmic pattern generators for forward locomotion in C. elegans

2019 ◽  
Author(s):  
Erick Olivares ◽  
Eduardo J. Izquierdo ◽  
Randall D. Beer
Keyword(s):  
Nerve Cord ◽  
Ventral Nerve Cord ◽  
Stretch Receptor ◽  
Rhythmic Pattern ◽  
Pacemaker Neurons ◽  
C Elegans ◽  
Forward Locomotion ◽  
Pattern Generators ◽  
Multiple Network ◽  
A Chain

AbstractMultiple mechanisms contribute to the generation, propagation, and coordination of the rhythmic patterns necessary for locomotion in Caenorhabditis elegans. Current experiments have focused on two possibilities: pacemaker neurons and stretch-receptor feedback. Here, we focus on whether it is possible that a chain of multiple network rhythmic pattern generators in the ventral nerve cord also contribute to locomotion. We use a simulation model to search for electrophysiological parameters of the anatomically constrained ventral nerve cord circuit that, when embodied and situated, can drive forward locomotion on agar, in the absence of pacemaker neurons or stretch-receptor feedback. Systematic exploration of the space of possible solutions reveals that there are multiple configurations that result in locomotion that is consistent with certain aspects of the kinematics of worm locomotion on agar. Analysis of the best solutions reveals that gap junctions between different classes of motorneurons in the ventral nerve cord can play key roles in coordinating the multiple rhythmic pattern generators.

scholarly journals Potential role of a ventral nerve cord central pattern generator in forward and backward locomotion in Caenorhabditis elegans

2018 ◽  
Vol 2 (3) ◽  
pp. 323-343 ◽  
Author(s):  
Erick O. Olivares ◽  
Eduardo J. Izquierdo ◽  
Randall D. Beer
Keyword(s):  
Nerve Cord ◽  
Ventral Nerve Cord ◽  
Computational Models ◽  
Neural Circuit ◽  
Central Pattern Generators ◽  
C Elegans ◽  
Segmentation Analysis ◽  
Pattern Generators ◽  
Neural Unit

C. elegans locomotes in an undulatory fashion, generating thrust by propagating dorsoventral bends along its body. Although central pattern generators (CPGs) are typically involved in animal locomotion, their presence in C. elegans has been questioned, mainly because there has been no evident circuit that supports intrinsic network oscillations. With a fully reconstructed connectome, the question of whether it is possible to have a CPG in the ventral nerve cord (VNC) of C. elegans can be answered through computational models. We modeled a repeating neural unit based on segmentation analysis of the connectome. We then used an evolutionary algorithm to determine the unknown physiological parameters of each neuron so as to match the features of the neural traces of the worm during forward and backward locomotion. We performed 1,000 evolutionary runs and consistently found configurations of the neural circuit that produced oscillations matching the main characteristic observed in experimental recordings. In addition to providing an existence proof for the possibility of a CPG in the VNC, we suggest a series of testable hypotheses about its operation. More generally, we show the feasibility and fruitfulness of a methodology to study behavior based on a connectome, in the absence of complete neurophysiological details.

scholarly journals Functionally asymmetric motor neurons coordinate locomotion of Caenorhabditis elegans

2018 ◽  
Author(s):  
Oleg Tolstenkov ◽  
Petrus Van der Auwera ◽  
Jana F. Liewald ◽  
Wagner Steuer Costa ◽  
Olga Bazhanova ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Gap Junctions ◽  
Motor Neurons ◽  
Nerve Cord ◽  
Ventral Nerve Cord ◽  
Body Wave ◽  
Central Pattern Generators ◽  
Physiological Data ◽  
C Elegans ◽  
Pattern Generators

SummaryInvertebrate nervous systems are valuable models for fundamental principles of the control of behavior. Ventral nerve cord (VNC) motor neurons in Caenorhabditis elegans represent one of the best studied locomotor circuits, with known connectivity and functional information about most of the involved neuron classes. However, for one of those, the AS motor neurons (AS MNs), no physiological data is available. Combining specific expression and selective illumination, we precisely targeted AS MNs by optogenetics and addressed their role in the locomotion circuit. After photostimulation, AS MNs induce currents in post-synaptic body wall muscles (BWMs), exhibiting an initial asymmetry of excitatory output. This may facilitate complex regulatory motifs for adjusting direction during navigation. By behavioral and photo-inhibition experiments, we show that AS MNs contribute to propagation of the antero-posterior body wave during locomotion. By Ca2+-imaging in AS MNs and in their synaptic partners, we also reveal that AS MNs play a role in mediating forward and backward locomotion by integrating activity of premotor interneurons (PINs), as well as in coordination of the dorso-ventral body wave. AS MNs do not exhibit pacemaker properties, but potentially gate VNC central pattern generators (CPGs), as indicated by ceasing of locomotion when AS MNs are hyperpolarized. AS MNs provide positive feedback to the PIN AVA via gap junctions, a feature found also in other locomotion circuits. In sum, AS MNs have essential roles in coordinating locomotion, combining several functions, and emphasizing the compressed nature of the C. elegans nervous system in comparison to higher animals.HighlightsA class of motor neurons with unidentified function – AS cholinergic motor neurons - was characterized in C. elegans.AS neurons show asymmetry in both input and output and are specialized in coordination of dorso-ventral undulation bends.AS neurons mediate antero-posterior propagation of the undulatory body wave during locomotion.AS neurons integrate signals for forward and reverse locomotion from premotor interneurons and may gate ventral nerve cord central pattern generators (CPGs) via gap junctions.

scholarly journals Mutations Affecting Nerve Attachment of Caenorhabditis elegans

Genetics ◽  
2001 ◽  
Vol 157 (4) ◽  
pp. 1611-1622 ◽  
Author(s):  
Go Shioi ◽  
Michinari Shoji ◽  
Masashi Nakamura ◽  
Takeshi Ishihara ◽  
Isao Katsura ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Nerve Cord ◽  
Ventral Nerve Cord ◽  
Body Wall ◽  
The Body ◽  
Genetic Loci ◽  
Muscle Attachment ◽  
C Elegans ◽  
Ventral Cord ◽  
Excretory Canal

Abstract Using a pan-neuronal GFP marker, a morphological screen was performed to detect Caenorhabditis elegans larval lethal mutants with severely disorganized major nerve cords. We recovered and characterized 21 mutants that displayed displacement or detachment of the ventral nerve cord from the body wall (Ven: ventral cord abnormal). Six mutations defined three novel genetic loci: ven-1, ven-2, and ven-3. Fifteen mutations proved to be alleles of previously identified muscle attachment/positioning genes, mup-4, mua-1, mua-5, and mua-6. All the mutants also displayed muscle attachment/positioning defects characteristic of mua/mup mutants. The pan-neuronal GFP marker also revealed that mutants of other mua/mup loci, such as mup-1, mup-2, and mua-2, exhibited the Ven defect. The hypodermis, the excretory canal, and the gonad were morphologically abnormal in some of the mutants. The pleiotropic nature of the defects indicates that ven and mua/mup genes are required generally for the maintenance of attachment of tissues to the body wall in C. elegans.

scholarly journals From head to tail: a neuromechanical model of forward locomotion in Caenorhabditis   elegans

2018 ◽  
Vol 373 (1758) ◽  
pp. 20170374 ◽  
Author(s):  
Eduardo J. Izquierdo ◽  
Randall D. Beer
Keyword(s):  
Caenorhabditis Elegans ◽  
Biomechanical Model ◽  
Neural Model ◽  
Cellular Level ◽  
The Body ◽  
Rhythmic Pattern ◽  
Unknown Parameters ◽  
Forward Movement ◽  
C Elegans ◽  
Forward Locomotion

With 302 neurons and a near-complete reconstruction of the neural and muscle anatomy at the cellular level, Caenorhabditis elegans is an ideal candidate organism to study the neuromechanical basis of behaviour. Yet despite the breadth of knowledge about the neurobiology, anatomy and physics of C. elegans , there are still a number of unanswered questions about one of its most basic and fundamental behaviours: forward locomotion. How the rhythmic pattern is generated and propagated along the body is not yet well understood. We report on the development and analysis of a model of forward locomotion that integrates the neuroanatomy, neurophysiology and body mechanics of the worm. Our model is motivated by experimental analysis of the structure of the ventral cord circuitry and the effect of local body curvature on nearby motoneurons. We developed a neuroanatomically grounded model of the head motoneuron circuit and the ventral nerve cord circuit. We integrated the neural model with an existing biomechanical model of the worm's body, with updated musculature and stretch receptors. Unknown parameters were evolved using an evolutionary algorithm to match the speed of the worm on agar. We performed 100 evolutionary runs and consistently found electrophysiological configurations that reproduced realistic control of forward movement. The ensemble of successful solutions reproduced key experimental observations that they were not designed to fit, including the wavelength and frequency of the propagating wave. Analysis of the ensemble revealed that head motoneurons SMD and RMD are sufficient to drive dorsoventral undulations in the head and neck and that short-range posteriorly directed proprioceptive feedback is sufficient to propagate the wave along the rest of the body. This article is part of a discussion meeting issue ‘Connectome to behaviour: modelling C. elegans at cellular resolution’.

Morphology of programmed cell death in the ventral nerve cord of Caenorhabditis elegans larvae

Development ◽  
1982 ◽  
Vol 67 (1) ◽  
pp. 89-100
Author(s):  
Alison M. G. Robertson ◽  
J. N. Thomson
Keyword(s):  
Cell Death ◽  
Caenorhabditis Elegans ◽  
Programmed Cell Death ◽  
Ultrastructural Study ◽  
Nerve Cord ◽  
Ventral Nerve Cord ◽  
Condensed Chromatin ◽  
C Elegans ◽  
Programmed Death ◽  
Selection Of

In the nematode C. elegans, cells undergoing programmed death in the developing ventral nerve cord were identified by Nomarski optics and prepared for ultrastructural study at various times after their birth in mitosis. The sequence of changes observed suggests that the hypodermis recognizes the dying cell before completion of telophase. The dying cell is engulfed and digestion then occurs until all that remains within the hypodermal cytoplasm is a collection of membranous whorls interspersed with condensed chromatin-like remnants. The process shares several features with apoptosis, the mode of programmed cell death observed in vertebrates and insects. The selection of cells for programmed death appears not to involve competition for peripheral targets.

scholarly journals The C. elegans CDK8 Mediator module regulates axon guidance decisions in the ventral nerve cord and during dorsal axon navigation

2013 ◽  
Vol 377 (2) ◽  
pp. 385-398 ◽  
Author(s):  
Andreas Steimel ◽  
Jinkyo Suh ◽  
Angela Hussainkhel ◽  
Samineh Deheshi ◽  
Jennifer M. Grants ◽  
...  
Keyword(s):  
Axon Guidance ◽  
Nerve Cord ◽  
Ventral Nerve Cord ◽  
C Elegans

scholarly journals A terminal selector prevents a Hox transcriptional switch to safeguard motor neuron identity throughout life

eLife ◽  
2020 ◽  
Vol 9 ◽  
Author(s):  
Weidong Feng ◽  
Yinan Li ◽  
Pauline Dao ◽  
Jihad Aburas ◽  
Priota Islam ◽  
...  
Keyword(s):  
Ion Channels ◽  
Motor Neurons ◽  
General Principle ◽  
Nerve Cord ◽  
Ventral Nerve Cord ◽  
Neurotransmitter Receptors ◽  
Dual Function ◽  
C Elegans ◽  
Neuronal Identity ◽  
Transcriptional Switch

To become and remain functional, individual neuron types must select during development and maintain throughout life their distinct terminal identity features, such as expression of specific neurotransmitter receptors, ion channels and neuropeptides. Here, we report a molecular mechanism that enables cholinergic motor neurons (MNs) in the C. elegans ventral nerve cord to select and maintain their unique terminal identity. This mechanism relies on the dual function of the conserved terminal selector UNC-3 (Collier/Ebf). UNC-3 synergizes with LIN-39 (Scr/Dfd/Hox4-5) to directly co-activate multiple terminal identity traits specific to cholinergic MNs, but also antagonizes LIN-39’s ability to activate terminal features of alternative neuronal identities. Loss of unc-3 causes a switch in the transcriptional targets of LIN-39, thereby alternative, not cholinergic MN-specific, terminal features become activated and locomotion defects occur. The strategy of a terminal selector preventing a transcriptional switch may constitute a general principle for safeguarding neuronal identity throughout life.

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