シンポジウム（Symposium）

Symposium Exploring the origin of brain and central nervous system through monitoring the neural activity of the whole animal シンポジウム個体レベルでの脳神経の活動イメージングから探る脳神経系の起源

7月27日（土）8:47～9:08　第1会場（朱鷺メッセ　4F　国際会議室） 3S01m-1 刺胞動物ヒドラの行動解析と神経活動の可視化から示唆される中枢神経系の起源 Hiroshi Shimizu（清水裕）¹，Yukihiko Noro（野呂行彦）²，Katsuhiko Mineta（峯田克彦）¹，Takashi Gojobori（五條堀孝）¹ ¹アブドラ国王科学技術大学 ²早稲田大学理工学術院　先端理工学部　生命医科学科 It is accepted that Central Nervous System (CNS) appeared as the result of evolution of body plan from radial to bilateral symmetry provoking the concentration of neurons along the midline forming ganglia. According to this view, nerve net in phylum Cnidaria that includes Hydra represents typical ancient system that was yet to develop CNS both functionally and anatomically. Indeed the nervous system of Hydra is characterized by its diffuse structure termed nerve net that has no concentration forming ganglia. From analysis of locomotory behavior of Hydra, we obtained evidence that a portion of nervous system is furnished with basic functions of CNS e.g. to receive sensory information as input while to send out locomotory signals as output. Unlike generally assumed, the population of neurons identified was distributed in the peduncle region which is located on the opposite side from the head. To monitor the neural activity of a whole Hydra polyp during locomotion, we constructed transgenic strains of Hydra by use of GCaMP6 method. Hydra is known to use multiple peptides as neurotransmitters and each of the peptides is synthesized in subpopulation of neurons in the animal showing distinct patterns of distribution. It is therefore a possibility that each of the transmitters have different regulatory functions in locomotion and other behaviors. A technical disadvantage of dealing with locmotory behavior of Hydra is that it is dynamic and spans in three-dimensional space. This constitutes obvious obstacle because precise monitoring of the neural activity requires that the tissue be fixed in a narrow space under the microscope to be in focus. We overcame this difficulty by constructing miniature Hydras to let the behavior occur in narrow space. Results obtained by the GCaMP6 procedure demonstrated that during overall locomotion the neural activity is the highest in the peduncle region of polyp thus in consistency with the evidence obtained by behavioral analysis.		7月27日（土）9:08～9:33　第1会場（朱鷺メッセ　4F　国際会議室） 3S01m-2 Breaking the Neural Code of a Cnidarian Rafael Yuste（Yuste Rafael） Columbia University Our goal is to ""break the code"" of the nervous system of the cnidarian Hydra vulgaris by imaging the activity of all of its neurons (Dupre and Yuste, 2017)and muscles (Szymanski and Yuste, 2019) while quantitatively measuring its behavior (Han et al., 2018) and building a computationally model of the animal that is explanatory and predictive. Hydra has one of the simplest nervous systems in the animal kingdom and therefore one that can be systematically analyzed and perhaps completely understood (Bosch et al., 2017). Principles learnt could be applied generally to other nervous systems. Bosch, T.C., Klimovich, A., Domazet-Loso, T., Grunder, S., Holstein, T.W., Jekely, G., Miller, D.J., Murillo-Rincon, A.P., Rentzsch, F., Richards, G.S., et al. (2017). Back to the Basics: Cnidarians Start to Fire. Trends Neurosci 40, 92-105.Dupre, C., and Yuste, R. (2017). Non-overlapping Neural Networks in Hydra vulgaris. Curr Biol 27, 1085-1097. Han, S., Taralova, E., Dupre, C., and Yuste, R. (2018). Comprehensive machine learning analysis of Hydra behavior reveals a stable basal behavioral repertoire. Elife 7. 10.7554/eLife.32605 Szymanski, J., and Yuste, R. (2019). Cellular multifunctionality in the muscle activity of Hydra vulgaris. (submitted).

7月27日（土）9:33～9:56　第1会場（朱鷺メッセ　4F　国際会議室） 3S01m-3 線虫の全脳イメージングから神経回路の情報処理を探る Yu Toyoshima（豊島有）¹，Hirofumi Sato（佐藤博文）¹，Manami Kanamori（金森真奈美）¹，Stephen Wu（Wu Stephen）²，Moon-Sun Jang（Jang Moon-Sun）¹，Yuko Murakami（村上悠子）³，Suzu Oe（大江紗）³，Terumasa Tokunaga（徳永旭将）⁴，Osamu Hirose（広瀬修）⁵，Sayuri Kuge（久下小百合）³，Takayuki Teramoto（寺本孝行）³，Yuishi Iwasaki（岩崎唯史）⁶，Ryo Yoshida（吉田亮）²，Takeshi Ishihara（石原健）³，Yuichi Iino（飯野雄一）¹ ¹東京大院理生物科学 ²情報・システム研究機構統計数理研究所 ³九州大理生物 ⁴九州工業大学情報工学研究院システム創成情報工学研究系 ⁵金沢大理工研究域生命理工学系 ⁶茨城大学工学部機械システム工学科 Recent advances in microscopy techniques enable whole-brain activity imaging in living animals including worms, flies, and small fishes. Among them, the nematode C. elegans has a unique property that all 302 neurons and their structural connectivity were identified by electron microscopy reconstruction. Such detailed knowledge opens up unique opportunities in neuroscience at both single-cell and network levels. We have intensively developed microscopy methods for whole-brain activity imaging of C. elegans. Time-lapse 3D images of the head region of living animals were obtained by using a custom spinning disk microscope. Genetically encoded calcium indicator YC2.60 were expressed with RFP in all neuronal nuclei. The nuclei were accurately detected and tracked by image analysis methods we developed. Annotating neuron identity is required to compare neural activities between different animals. We systematically identified neurons in the head region of 311 adult worms using 35 kinds of cell-specific promoters and created a dataset of the positions of the neurons. The large positional variations disrupt position-based annotation, and we utilize cell-specific promoter-driven fluorescence as a landmark. Integrating these technique enables us to obtain whole-brain neuronal activity data with annotation. Most of neurons showed synchronized activity independently of external stimuli. To interpret the complex activities, we employed independent component analysis and found that independent components reflecting activities of sensory and motor neurons were shared between animals. Additionally, we applied cross-embedding analysis and confirmed that a part of sensory neurons including the salt-sensing ASER neuron can predict the timing of stimulation compared to control, indicating that these neurons encode information of external stimuli. We found that a part of interneurons and motor neurons can predict the movement compared to the control, indicating that these neurons encode information of motor output. We also found some neurons have predictability for both stimulation and movement, suggesting that the neurons may convert sensory information to motor output. Through these analyses, we have elucidated the mechanisms of the neural information processing.		7月27日（土）9:56～10:19　第1会場（朱鷺メッセ　4F　国際会議室） 3S01m-4 ショウジョウバエ運動回路の胚発生: 同調神経活動の出現と感覚フィードバックの役割 Akinao Nose（能瀬聡直）^1,2，Xiangsunze Zeng（曽祥孫澤）¹，Tappei Kawasaki（川崎達平）¹，Kengo Inada（稲田健吾）³，Hokto Kazama（風間北斗）³ ¹東京大院新領域創成科学複雑理工 ²東京大院理物理 ³理研CBS 知覚神経回路機構 Animals' behavioral patterns form in a gradual manner during late embryogenesis as the innervation of the somatic musculature and connectivity within the central nervous system develop. Initial uncoordinated or premature motor activity emerges while the animals are still in the womb or egg and reflects the onset of functional locomotor circuits. For instance, in the spinal cord of vertebrates, initial bursts occur in local groups of neurons and induce contractions of the target muscles. It has been proposed that such premature motor activities, via sensory feedback of the muscular movement, instruct the formation of functional locomotor circuits. However, little is known about the underlying circuit mechanism and molecular basis. In this study, we use peristaltic locomotion of larval Drosophila as a model to investigate the emergence of coordinated neural population activities and the role of proprioceptive experience in development of locomotor circuits. We carry out calcium imaging of the isolated central nervous system to study the development of the central pattern generators (CPGs) that drive peristaltic locomotion. We find that motor activity initially appears sporadically in one or a few cells, then develops into premature waves that travel a few segments and finally matures to form complete waves towards the end of embryogenesis. We also show that in nompC or tmc mutants, which lack sensory feedback of muscular movement, the CPGs fail to develop properly. Our results of dye-coupling also suggest that gap-junctional transmission in a target interneuron of the proprioceptor is required for proper function of the CPGs. Based on these and other results, we will discuss how gap junctions and sensory feedback might regulate the development of the functional locomotor circuits from the behavioral and physiological perspectives.

7月27日（土）10:19～10:42　第1会場（朱鷺メッセ　4F　国際会議室） 3S01m-5 ゼブラフィッシュ捕獲行動を司る機能的神経回路の可視化 Akira Muto（武藤彩）国立遺伝研個体遺伝初期発生 In the feeding behavior of diurnal animals, visual recognition of food or prey plays an essential role in the generation of motivation for prey capture. This motivationalfeeding behavior is under regulation of the hypothalamus. Because fish larvae receive no parental care, this visually-driven feeding behavior needs to be hard-wired, and also should be adaptive to ever-changing feeding environments. To understand relationships between cognitive brain function and behavior, we study prey capture in zebrafish as a model system. Our approach is to combine visualization of neuronal activity and behavioral observation in zebrafish larvae. Neuronal activity in specific populations of cells can be monitored with a genetically encoded calcium probe, GCaMP, which is specifically expressed using a genetic method, Gal4-UAS system. By employing this methodology, neuronal activity during visual perception of prey has been demonstrated to be present on a visuotopic map of the optic tectum. How does visual perception of prey lead to feeding behavior? How is the hypothalamic feeding center involved in this neuronal pathway? To answer these questions, we performed real-time imaging of neuronal activity using freely-behaving or constrained zebrafish. We identified a nucleus in the pretectal area as a prey detector, which responded to prey or prey-like visual stimuli. By Ca imaging and laser ablation experiments, we further showed that the pretecto-hypothalamic circuit is essential for feeding behavior. Based on our results, we conclude that the pretecto-hypothalamic circuit plays a crucial role to convey visual information to the feeding center. This pathway possibly converts visual food detection into feeding motivation in zebrafish. By conducting calcium imaging of genetically specified neurons during feeding behavior, we aim to understand cognitive brain function in this goal-directed, motivational behavior. References: Muto et al., Proc Natl Acad Sci U S A. 2011 Mar 29;108(13):5425-30. Muto et al., Curr Biol. 2013 Feb 18;23(4):307-11. Muto et al., Nat Commun. 2017 Apr 20;8:15029.