Neuron
Volume 80, Issue 4, 20 November 2013, Pages 920-933
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Article
Locomotor Rhythm Generation Linked to the Output of Spinal Shox2 Excitatory Interneurons

https://doi.org/10.1016/j.neuron.2013.08.015Get rights and content
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Highlights

  • The transcription factor Shox2 defines a subset of spinal excitatory neurons

  • Shox2 neurons define distinct microcircuits in the spinal locomotor network

  • Subsets of Shox2 neurons are involved in rhythm generation

Summary

Locomotion is controlled by spinal networks that generate rhythm and coordinate left-right and flexor-extensor patterning. Defined populations of spinal interneurons have been linked to patterning circuits; however, neurons comprising the rhythm-generating kernel have remained elusive. Here, we identify an ipsilaterally projecting excitatory interneuron population, marked by the expression of Shox2 that overlaps partially with V2a interneurons. Optogenetic silencing or blocking synaptic output of Shox2 interneurons (INs) in transgenic mice perturbed rhythm without an effect on pattern generation, whereas ablation of the Shox2 IN subset coinciding with the V2a population was without effect. Most Shox2 INs are rhythmically active during locomotion and analysis of synaptic connectivity showed that Shox2 INs contact other Shox2 INs, commissural neurons, and motor neurons, with preference for flexor motor neurons. Our findings focus attention on a subset of Shox2 INs that appear to participate in the rhythm-generating kernel for spinal locomotion.

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The authors contributed equally to this paper