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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