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Sculpting the neuronal intracellular environment: from single molecule behavior to local signal integration
Sculpting the neuronal intracellular environment: from single molecule behavior to local signal integration

開催日 2014/9/12
時間 9:00 - 11:00
会場 Room B(501)
Chairperson(s) 合田 裕紀子 / Yukiko Goda (理化学研究所 脳科学総合研究センター シナプス可塑性・回路制御研究チーム / RIKEN, Brain Science Institute, Japan)
瀬藤 光利 / Mitsutoshi Setou (浜松医科大学 解剖学講座 細胞生物学分野 / Department of Cell Biology and Anatomy Hamamatsu University School of Medicine, Japan)

Calcium signaling in dendrite development and remodeling

  • S2-B-1-3
  • 榎本 和生 / Kazuo Emoto:1 
  • 1:東京大学大学院理学系研究科 / Graduate School of Science, The University of Tokyo, Japan 

Nervous system development relies on a balance between progressive and regressive events. After progressive events such as axon/dendrite outgrowth and synapse formation, neurons refine their connections through regressive events such as pruning of axons and dendrites. Of these two, dendrite pruning is less well understood. In the vertebrate nervous system, developmental dendrite pruning has been described extensively in both retinal ganglion cells in the retina and mitral cells in the olfactory bulb, in which neurons prune their dendrites, without loss of themselves, to eliminate unwanted connections that are initially formed during development. Thus, proper dendrite pruning critically depends on local activation of the elimination machinery in unwanted dendrites, but our understanding of locally acting mechanisms involved in this process remains incomplete.
We have been working on how neurons can selectively eliminate unnecessary dendritic branches using Drosophila sensory neurons as a model system, and found that compartmentalized calcium transients in dendritic branches act as temporal and spatial cues to trigger pruning. By performing long-term in vivo imaging, we show that calcium transients occur in dendritic branches, but not in the soma or axon which exhibits no pruning, at ~3 hours prior to branch elimination. The compartmentalized calcium transients are induced in part by a local increase of dendritic excitability, which thereby activates calcium influx via voltage-gated calcium channels (VGCCs); blockade of VGCC activity impairs dendrite pruning. Further genetic analyses suggest that the calcium-activated protease calpain functions downstream of the calcium transients to promote dendrite pruning. Our findings reveal the importance of compartmentalized sub-dendritic calcium signaling in spatio-temporally selective elimination of dendritic branches.

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