FY2019 Annual Report

Neural Circuit Unit
Professor Yutaka Yoshida

Abstract

The Neural Circuit Unit is interested in understanding the neural circuits underlying locomotor and skilled motor behaviors in mammals, and the precise signaling by spinal motor neurons required for coordinating the upwards of fifty different muscle groups in our limbs to create movement.  The motor neuron pools projecting axons to specific muscles are located in clusters within the ventral spinal cord, which are regulated by synaptic inputs from three main pathways: local interneuron circuits, proprioceptive sensory feedback, and descending fibers from the brain, including the corticospinal tract.  The Unit primarily focuses on formation, function, and regeneration of descending and sensory-motor circuits.

1. Staff

• Yutaka Yoshida, Professor
• Kumiko Saitou, Postdoctoral Scholar
• Akihiro Furuya, Postdoctoral Scholar
• Nedjeljka Ivica, Postdoctoral Scholar
• Tomoe Owan, Research Unit Administrator

2. Collaborations

2.1 Evolutionarily distinct, species-specific motor circuits

• Description: Comparison of mRNAs in neurons within motor circuits between rodents and primates
• Type of collaboration: Joint research
• Researchers:
  • Professor Masahiko Takada, the Primate Research Institute of the Kyoto University

2.2 To understand how motor circuits are activated during motor behaviors

• Description: Measuring of neural activity during motor behaviors
• Type of collaboration: Joint research
• Researchers:
  • Professor Kenichi Ohki, University of Tokyo

3. Activities and Findings

Although we showed some cellular and molecular mechanisms underlying monosynaptic connections between motor neurons and corticospinal neurons in mice and primates (Gu et al., Science, 2017), corticospinal circuits also differ anatomically between primates and mice.  In primates, corticospinal axon bundles are located only in the ventral and lateral funiculi and extensive corticospinal axon collaterals are observed in the ventral spinal cord, whereas the CS axon bundles of mice, including those of the PlexA1 mutants, are primarily located in the dorsal funiculus.  In addition, amount of corticospinal axons in the ventral spinal cord seems to be different between PlexA1 mutant mice and primates.  Thus, other molecules in addition to PlexA1 must be involved in driving species-specific differentiation in CS circuitry.  We are in the process of collecting mRNAs from mouse and primate corticospinal neurons for single cell RNA-seq to determine how many classes of corticospinal neurons exist in mice and primates.  In addition, we plan to compare mRNAs from the mouse and primate corticospinal neurons to determine how evolutionally-different CS circuits developed.  Then we will determine expression patterns of genes that are differentially expressed in corticospinal neurons between mice and primates by in situ hybridization. These analyses will reveal how corticospinal circuits are differentially formed and function between mice and primates. 

4. Publications

Nothing to report

5. Intellectual Property Rights and Other Specific Achievements

Nothing to report

6. Meetings and Events

Nothing to report

7. Other

Nothing to report.