シンポジウム
19 メカノニューロバイオロジー 〜力を制するもの脳を制す〜
19 Mechano-neurobiology ~ Those who rule the force would rule the brain~
座長：見學 美根子（京都大学高等研究院）・佐藤 純（金沢大学 新学術創成研究機） |
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| 2022年7月2日 14:03～14:25 ラグナガーデンホテル 羽衣：東 第8会場
3S08a-01
メカノセンサーチャネルPIEZO1が大脳発生を制御する
Mechanosensor channel PIEZO1 regulates cerebral development
*岡本 麻友美(1)、野々村 恵子(2,3)、島村 司(1)、宮田 卓樹(1)
1. 名古屋大学大学院医学系研究科、2. 東京工業大学生命理工学院、3. 自然科学研究機構基礎生物学研究所初期発生部門
*Mayumi Okamoto(1), Keiko Nonomura(2,3), Tsukasa Shimamura(1), Takaki Miyata(1)
1. Grad Sch Med, Nagoya Univ, Nagoya, Japan, 2. Sch Life Sci Tech, Tokyo Tech, 3. Div Embryology, NIBB
Keyword: neural progenitor cells, cerebral development, PIEZO1
Mechanical stimuli control a variety of biological functions, including development and homeostasis. Cerebral tissues are composed of highly dense and dynamic neural progenitor cells, and various types of mechanical forces are expected to be present there. However, it is not well understood whether mechanosensation is involved in cell proliferation/differentiation of neural progenitor cells and cerebral tissue formation/maintenance. In this study, we focused on PIEZO1, a mechanosensor channel involved in force sensing and response among various types of cells. We found that PIEZO1 is expressed at the apical endfeet of neural progenitor cells during cerebral development. In order to ask the importance of PIEZO1 in cerebral development, we generated and analyzed neural progenitor-specific Piezo1 conditional knockout mice. Piezo1-deficient mice showed enlargement of the cerebral ventricle and reduction of the ventricular zone at the embryonic stage. Analysis of Piezo1-deficient mice suggests that PIEZO1 functions in (i) the control of the ventricular surface contractility and (ii) the control of cell production in neural progenitor cells during cerebral development. We will discuss the first evidence for the contribution of PIEZO1 to cerebral development. | | 2022年7月2日 14:25～14:47 ラグナガーデンホテル 羽衣：東 第8会場
3S08a-02
幾何学分割による複眼のタイリング機構
Tiling mechanisms of the compound eye through geometrical tessellation
*佐藤 純(1)、林 貴史(1)、須志田 隆道(2)、秋山 正和(3)、栄 伸一郎(4)
1. 金沢大学、2. サレジオ工業高等専門学校、3. 富山大学、4. 北海道大学
*Makoto Sato(1), Takashi Hayashi(1), Sushida Takamichi(2), Akiyama Masakazu(3), Ei Shi-Ichiro(4)
1. Kanazawa University, 2. Salesian Polytechnic, 3. Toyama University, 4. Hokkaido University
Keyword: tiling, Drosophila, compound eye, Voronoi diagram
Tilling patterns are found in many biological structures such as compound eye, auditory epithelium and microcolumns in the cerebral cortex. Among them, hexagonal tilling is dominant probably because it is superior to the other tilling patterns in terms of physical properties such as structural strength, boundary length and space filling. Additionally, the hexagonal tiling pattern may be beneficial for information processing of neural circuits.
The Drosophila compound eye is made from simple ommatidial units showing regular hexagonal pattern and is an ideal model to understand the mechanism of tiling. Interestingly, it also shows tetragonal or irregular patterns in some mutant backgrounds. Here, we propose a universal mechanism of ommatidial tilling. Voronoi diagram is often used to equally divides multiple areas according to the distance from the center of each area. We found that the wildtype hexagonal pattern and mutant tetragonal pattern perfectly fit with Voronoi diagram. Incorporating the tissue-wide tension along the dorsal-ventral axis observed in vivo, the hexagonal pattern is transformed to the tetragonal pattern.
How does ommatidial shape obey the geometrical Voronoi patterns? To answer this question, we focused on mutant eyes, in which the tilling pattern becomes stochastic. Surprisingly, such a stochastic ommatidial pattern also fit with Voronoi diagram except for occasional mismatching found in smaller and larger ommatidia. The growth of ommatidia, which is largely affected by the number of cells within individual ommatidia, may play critical roles. We therefore incorporated the differential growth of ommatidia into Voronoi diagram. Compared with standard Voronoi diagram, we found that weighted Voronoi diagram, in which the concentric growth rate is proportional to the ommatidial size, nicely fit with the stochastic mutant pattern. Thus, physical stretch of the eye tissue and geometrical tessellation through the concentric growth of ommatidia co-operatively determine ommatidial tiling patterns. | | 2022年7月2日 14:47～15:09 ラグナガーデンホテル 羽衣：東 第8会場
3S08a-03
脳組織において神経細胞移動を駆動するメカノセンシング／レスポンスの分子機構
Molecular mechanisms of mechano-sensing / -response for neuronal migration in 3D brain tissue
*中澤 直高(1)、Grenci Gianluca(2)、野々村 恵子(3)、栗栖 純子(1)、見學 美根子(1,4)
1. 京都大 物質-細胞統合システム拠点、2. シンガポール国立大 メカノバイオロジー研究所、3. 東京工業大 生命理工学院、4. 京都大学大学院 生命科学研究科
*Naotaka Nakazawa(1), Gianluca Grenci(2), Keiko Nonomura(3), Junko Kurisu(1), Mineko Kengaku(1,4)
1. iCeMS, Kyoto Univ, Kyoto, Japan, 2. Mechanobiology Institute, NUS, Singapore, 3. Tokyo Institute of Technology, Tokyo, Japan, 4. Grad Sch Biostudy, Kyoto Univ, Kyoto, Japan
Keyword: Neuronal migration, Mechano-sensing, Actomyosin, Mechano-response
The migration of newly born neurons in the neural tissue is a critical step during brain cortex development. Neurons sometimes migrate in confined spaces surrounded by the extracellular matrices (ECM) and other cells in the brain tissues. Such confinement induces mechanical stress to the cells, which results in the induction of mechano-responses. However, how these responses contribute to brain tissue development is largely elusive. Our recent studies using high-resolution time-lapse microscopy have revealed dynamic nuclear motions and shape changes during neuronal migration in confined spaces in the emerging cerebellar cortex (Wu et al., 2018). In the cerebellar granule cells on a flat surface, F-actin and Myosin II motors localize at the nuclear front and generate the traction force for nuclear translocation (Umeshima et al., 2018). On the other hand, previous studies using olfactory bulb interneurons and inhibitory interneurons from the medial ganglionic eminence have shown the accumulation of F-actin and Myosin II at the nuclear rear during migration in 3D environment. Unlike the previous view that the distinct cell types adopt differential mechanisms of nuclear migration, we hypothesized that the mechanical stress from the extracellular environment may trigger different modes of neuronal migration. To test this hypothesis, we have developed culture substrates with a microchannel device which enable recapitulation of neuronal migration in confined interstitial spaces in the developing neural tissue. Our data suggest that cerebellar granule cells switch its migration modes by activating actomyosin in distinct subcellular compartments in response to mechanical stress in opened and confined spaces. Further, neuronal migration in 3D is initiated by activating a mechano-sensitive channel triggered by mechanical stress on the cell soma. Our findings indicate that mechano-sensing / -response mechanisms are critical for neuronal migration in confined spaces during brain development. | | 2022年7月2日 15:09～15:31 ラグナガーデンホテル 羽衣：東 第8会場
3S08a-04
Mechanical actions of dendritic-spine enlargement and the discovery of the PREST mechanism in the presynaptic terminals in the CNS.
*Hasan Ucar(1,2), Satoshi Watanabe(1,3), Jun Noguchi(1,3), Sho Yagishita(1,2), Noriko Takahashi(1,4), Haruo Kasai(1,2)
1. Laboratory of Structural Physiology, Center for Disease Biology and Integrative Medicine, Faculty of Medicine, The University of Tokyo, 2. International Research Center for Neurointelligence (WPI-IRCN), UTIAS, The University of Tokyo, 3. Department of Ultrastructural Research, National Institute of Neuroscience, National Center of Neurology and Psychiatry, 4. Department of Physiology, Kitasato University School of Medicine
Keyword: PREST (pressure sensation and transduction), glutamate release, synaptic plasticity, presynaptic terminal
Dendritic spines in the CNS enlarge during learning. However, within the compact brain tissue with the tight synaptic clefts, the spine enlargement may have mechanical effects on the presynaptic terminals. In this work, we studied this novel phenomenon and we have identified a mechanosensory and transduction mechanism where presynaptic activity is enhanced by sensing the mechanical pressure emerging from spine enlargement.
We used the Schaffer collateral (SC) innervating CA1 pyramidal neurons in hippocampal slice cultures and we have found that fine and transient pushing of the boutons (0.1 µm) by a glass pipette markedly promoted the evoked neurotransmitter release and vesicle binding in the presynaptic terminals. To our surprise, both effects persisted over 20 min. Here, transmitter release was measured by presynaptic expression of iGluSnFR, and vesicle binding was estimated by the assembly of soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins, whose Förster resonance transfer (FRET). between Syntaxin1A and VAMP2. was measured with fluorescence lifetime imaging (FLIM).
The presynaptic FRET increase was independent of cytosolic Ca2+, but dependent on the assembly of SNARE proteins and polymerization of actin fibers in the boutons. Importantly, a low hypertonic sucrose solution caused facilitatory effects on both the FRET and evoked release without inducing spontaneous release, making a striking contrast with a high hypertonic sucrose solution which induces exocytosis by itself.
Finally, we identified synapse candidates between SC and CA1 pyramidal neurons by overlapping optical signals of boutons (expressing trans-SNARE or iGluSnFR probe) and dendritic spines (filled by Alexa-dye by whole-cell patch-clamping). In this experiment set, the spine enlargement induced by two-photon glutamate uncaging enhanced evoked release and FRET when the spines pushed the boutons by their elongation. This enhancement was not observed with enlarging spines without an elongation. In summary, we have found a PREST (Pressure Sensation and Transduction) mechanism in the boutons which enables boutons to sense mechanical forces for enhancing evoked release by increasing the ternary-SNARE formation. And we suggest that the spine enlargement, in addition to its roles in the well-recognized postsynaptic mechanisms, can potentiate the synaptic transmission by direct mechanical coupling of the presynaptic terminal. | | 2022年7月2日 15:31～15:53 ラグナガーデンホテル 羽衣：東 第8会場
3S08a-05
ヒトの神経分化におけるメカニカルファクターの意義を解明するには？
How can we elucidate the significance of mechanical factors in human neural differentiation?
*小曽戸 陽一(1)
*Yoichi Kosodo(1)
1. Korea Brain Research Institute
Keyword: Mechanotransduction, Neural differentiation, Stiffness, Biomaterial
The mechanical properties of the extracellular microenvironment, including its stiffness, play a crucial role in stem cell fate determination. In the case of developing brain, we have demonstrated that spatiotemporal diversities in stiffness exist in mammalian cortex (Iwashita et al, 2014; Iwashita et al, 2020) and hippocampus (Ryu et al, 2021). Nevertheless, it remains largely unclear how stiffness regulates stem cell fate towards specific neural lineages, especially in human. Uncovering the role of stiffness to regulate human neural lineage would bring us fruitful knowledge not only in the aspect of developmental neurobiology but also therapeutic strategy for neural regeneration. Toward the aim, we have designed a reconstitution assay system to be employed for neural differentiation from human pluripotent stem cells by establishing a culture substrate using tilapia collagen (Iwashita et al, 2019). By adding crosslinkers, we successfully obtained gels that are similar in stiffness to living brain tissue (150-1500 Pa). Subsequently, we examined the capability of the gels serving as a substrate for stem cell culture and the effect of stiffness on human neural lineage, identifying that exposure to gels with a higher stiffness during the early period of neural induction promoted the production of dorsal cortical neurons. For further understandings, we are currently developing quantitative approaches to evaluate neural differentiation status. Together, our attempts will elucidate the significant role of the extracellular mechanical factors for human neural lineage specifications. | | | |
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