「神経科学セミナー」 - 新学術創成研究機構

新学術創成研究機構
革新的統合バイオ研究コア数理神経科学研究ユニット
「神経科学セミナー」
Institute for Frontier Science Initiative
Innovative Integrated Bio-Research Core
Mathematical Neuroscience Unit
<Neuroscience Seminar>
平成２８年２月１２日（金）１６時〜１８時
十全記念スタジオ（宝町医学図書館２階）
Feb. 12th (Fri.), 2016 16:00-18:00
Juzen Studio (Medical School Library)
演者：
今井猛先生
理化学研究所多細胞システム形成研究センター（理研CDB）
筒井秀和先生北陸先端科学技術大学院大学マテリアルサイエンス研究科
吉田知之先生富山大学大学院医学薬学研究部分子神経科学講座
連絡先：新学術創成研究機構佐藤純
TEL: 076-265-2843
E-mail: [email protected]
講演要旨：
1. Temporal odor coding by neuronal oscillations
Dr. Takeshi Imai
(RIKEN CDB)
Sensory information is represented not only as firing rate (rate coding), but also as temporal
patterns (temporal coding) of activity in neurons. In the rodent olfactory bulb, odor produces
rich temporal patterns of activity in mitral/tufted cells and aid sensory discrimination;
however, origins and roles of the temporal patterns remain enigmatic. Here we show that the
precise temporal odor coding requires neuronal oscillations driven by sensory neurons. The
mechanosensitivity in olfactory sensory neurons drove widespread but glomerulus-specific
oscillations locked to sniff cycles in mitral/tufted cells. The odor stimuli produced
glomerulus- and odor-specific phase shifts in oscillations, which were invariant across wide
range of odor concentrations and sniff cycles, contrary to the labile nature of rate coding. The
loss of airflow-driven oscillations impaired stability of the temporal coding. We propose that
the phase odor coding is a robust encoding strategy for maintaining an odor identity under
dynamically fluctuating environment during behavior.
2. Capturing impulses and crystals in live cells
Dr. Hidekazu Tsutsui (JAIST)
The voltage sensor domain is a functional module that undergoes structural transitions in
response to membrane potential changes and regulates its effectors, thereby playing a crucial
role in amplifying and decoding membrane electrical signals. While recent crystallographic
studies have revealed atomic scale snapshots of voltage sensor domains, dynamic aspects
during the transitions have not been fully addressed. We have been interested in both to obtain
insights for the voltage-induced transition mechanisms and to generate protein-based optical
sensors for the detection of cellular electrical activities. In this talk, I will show our recent
results regarding these topics. Also, I will also talk on some interesting phenomena –
spontaneous crystallization of fluorescence proteins in live cells including neurons – which
we encountered unexpectedly through investigating photochemistry in photoconvertible
fluorescence proteins.
3. Regulation of neuronal synapse organizer function
by alternative splicing of microexons
Dr. Tomoyuki Yoshida (University of Toyama)
Neuronal cells in the brain are connected by synapses in a spatiotemporally organized manner
to form the neural networks for higher-order brain functions. Synapse formation is partly
mediated by a small subset of trans-synaptic cell adhesion molecules called synapse
organizers that have ability to induce pre- and postsynaptic differentiation. However,
molecular mechanisms by which synapse organizers ensure the specificity of extremely
diverged but highly organized synaptic connections in the brain remain elusive. We found that
protein tyrosine phosphatase (PTP) δ, one of presynaptic synapse organizers, existed in
multiple variants generated by insertions of 3, 6 and 4 amino-acid residue peptides (termed
mini-exon peptides) in two alternative splicing sites in the extracellular immunoglobulin
(Ig)-like domains. At least 8 splice variants in the Ig-like domains of PTPδ were expressed in
the developing mouse brains and proportions of these splice variants varied in the brain
regions and developmental stages. Furthermore, the excitatory or inhibitory synaptogenic
activities of PTPδ varied depending on the combinations of mini-exon peptides inserted into
the alternative splicing sites. Structural analyses of synapse-organizing complex of PTPδ and
its ligands revealed the role of mini-exon peptides on the ligand recognition and synaptic
differentiation. These results suggest that the choice of mini-exons by alternative splicing may
be determinants for selective pairing between PTPδ variants and their corresponding
postsynaptic ligands to ensure the target specific synapse formation in the brain.

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