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Elife. 2018 Sep 11;7. pii: e34997. doi: 10.7554/eLife.34997.

Functionally asymmetric motor neurons contribute to coordinating locomotion of Caenorhabditis elegans.

Author information

1
Buchmann Institute for Molecular Life Sciences, Goethe University, Frankfurt, Germany.
2
Institute for Biophysical Chemistry, Goethe University, Frankfurt, Germany.
3
Cluster of Excellence Frankfurt Macromolecular Complexes, Goethe University, Frankfurt, Germany.
4
Department of Biology, Functional Genomics and Proteomics Unit, Katholieke Universiteit Leuven, Leuven, Belgium.
5
International Max Planck Research School in Structure and Function of Biological Membranes, Frankfurt, Germany.

Abstract

Locomotion circuits developed in simple animals, and circuit motifs further evolved in higher animals. To understand locomotion circuit motifs, they must be characterized in many models. The nematode Caenorhabditis elegans possesses one of the best-studied circuits for undulatory movement. Yet, for 1/6th of the cholinergic motor neurons (MNs), the AS MNs, functional information is unavailable. Ventral nerve cord (VNC) MNs coordinate undulations, in small circuits of complementary neurons innervating opposing muscles. AS MNs differ, as they innervate muscles and other MNs asymmetrically, without complementary partners. We characterized AS MNs by optogenetic, behavioral and imaging analyses. They generate asymmetric muscle activation, enabling navigation, and contribute to coordination of dorso-ventral undulation as well as anterio-posterior bending wave propagation. AS MN activity correlated with forward and backward locomotion, and they functionally connect to premotor interneurons (PINs) for both locomotion regimes. Electrical feedback from AS MNs via gap junctions may affect only backward PINs.

KEYWORDS:

C. elegans; Ca2+ imaging; behavioral analysis; gap junctions; locomotor circuit; neuroscience; optogenetics

PMID:
30204083
PMCID:
PMC6173582
DOI:
10.7554/eLife.34997
[Indexed for MEDLINE]
Free PMC Article

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