一般口演
軸索輸送と細胞骨格 / 髄鞘機能
Axonal Transport and Cytoskeleton / Myelin Mechanisms
座長：見學 美根子（京都大学高等研究院） |
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| 2022年7月2日 17:10～17:25 沖縄コンベンションセンター 会議場B2 第5会場
3O05e2-01
若年性遺伝子BEX1は一次線毛の形成に必須である
BEX1, a juvenility-associated gene, is essential for ciliogenesis.
*森 雅樹(1,2)
1. 国立循環器病研究センター研究所、2. 滋賀医科大学 神経難病研究センター
*MASAKI MORI(1,2)
1. National Cerebral and Cardiovascular Center Research Institute, 2. Shiga University of Medical Science
Keyword: Juvenility, primary cilia, BEX1, Intrinsically disordered protein (IDP)
Children’s nervous systems possess numerous advantages that adults’ do not. These advantages include properties of organ size control, maturation, learning, recovery and so on. The underlying mechanism for the children’s advantages is not fully understood. We identified juvenility-associated genes (JAGs) as building blocks for the children’s inherent properties. In this study, we show a new role for BEX1, a JAG, that was widely expressed in juvenile organs. Subcellular localization studies reveal BEX1 localizes to the basal body in a cell density-dependent manner and is indispensable for primary cilia formation. Bex1 knockout mice exhibit loss of primary cilia at retinal pigment epithelium (RPE) and striatum. The Bex1 mutant mice present ciliopathy phenotypes including malformation of RPE, polycystic kidney disease and cerebellar hypoplasia. The constellation of the symptoms implied the manifestations were similar to those observed in Joubert syndrome. Circular dichroism and nuclear magnetic resonant (NMR) spectroscopies reveal that BEX1 harbor the properties of being an intrinsically disordered protein (IDP). NMR spectroscopies revealed that BEX1 protein bound to GTP, the energy substrate for tubulin polymerization. Recombinant BEX1 protein is capable of forming the biomolecular concentrates that facilitate tubulin polymerization in the reconstituted system. Thus, we demonstrate that BEX1 possess physicochemical properties as IDP and provides a reaction field at the ciliary bases that is indispensable for ciliogenesis. | | 2022年7月2日 17:25～17:40 沖縄コンベンションセンター 会議場B2 第5会場
3O05e2-02
Structural perspective of ankyrin-mediated complex assembly in neuronal polarity maintenance and synaptic transmission
*Wang Chao(1)
*Chao Wang(1)
1. University of Science and Technology of China, Hefei, China
Keyword: Ankyrins, Neuronal polarity, Axon initial segment, protein structure
Ankyrin-G (AnkG), a highly enriched scaffold protein in the axon initial segment (AIS) of neurons, functions to maintain axonal polarity and the integrity of the AIS. AnkG interacts with diverse proteins including voltage-gated ion channels, cell adhesion molecules, cytoskeleton proteins and regulatory proteins, and serves as the main organizer at the AIS. The AIS is responsible for action potential generation and critical for neuronal polarity establishment and maintenance. Dysfunction of ankyrin-mediated protein complex is closely related to severe psychiatric disorders in human. In this talk, I will focus on the mechanisms of ankryin complex assembly from a biochemist and structural perspective. AnkG regulates selective intracellular cargo sorting at the AIS via interaction with dynein regulator Ndel1. Our solve crystal structure of Ankyrin/Ndel1 complex provided the molecular details of the interaction and we showed the cargo sorting is disrupted by introducing an inhibitory peptide blocking AnkG/Ndel1 complex, shedding lights on maintenance of axonal polarity. AnkG can strongly interact with GABARAP, a protein known to support GABAA receptors on the cell membrane. Using a giant AnkG-derived peptide to disrupt GABARAP/ GABAA receptor complex, we demonstrated that mIPSC amplitudes are decreased in brain slice. We solved GABARAP–GABAA receptor crystal structure and further showed GABARAP functions to stabilize GABA receptors via a trafficking pathway rather than by blocking endocytosis. We also investigate the interaction between AnkG and Nfasc-186, a cell adhesion molecule enriched at the AIS. We successfully solve the complex structure of AnkG/Nfasc-186 and uncover the binding mechanisms. | | 2022年7月2日 17:40～17:55 沖縄コンベンションセンター 会議場B2 第5会場
3O05e2-03
中枢神経系の髄鞘形成不全を呈するTeneurin-4欠損マウスでの小径軸索メンテナンス機構
The Maintenance of Small Caliber Axons in Teneurin-4 Deficient Mice with the Congenital Hypomyelination in the CNS
*鈴木 喜晴(1)、高橋 りこ(1)、齋藤 日菜子(1)、細田 ゆき奈(1)、林 千香子(1)
1. 東京医科歯科大学
*Nobuharu Suzuki(1), Riko Takahashi(1), Hinako Saito(1), Yukina Hosoda(1), Chikako Hayashi(1)
1. Tokyo Medical and Dental University
Keyword: Myelin, Axon, Oligodendrocyte
In the CNS, the axonal tracts with various caliber sizes are myelinated by oligodendrocytes and rapidly conduct action potential. In addition, myelin metabolically supports axonal homeostasis, therefore, defects of myelination result in axonal degeneration and loss. In demyelinating and dysmyelinating diseases, such as multiple sclerosis and leukodystrophy, smaller caliber axons are more vulnerable with the defects of myelin, and axonal loss is eventually observed. The mutant mouse line, whose expression of the transmembrane protein teneurin-4 (Ten-4) is knocked out, displays CNS hypomyelination particularly in small axons regions, including the corticospinal tract (CST) and the fasciculus gracilis (FG), due to the absence of a subpopulation of oligodendrocytes that myelinate small caliber axons. Since Ten-4 deficient (-/-) mice survive longer than a year, they are a good model to monitor axonal change after the myelination defect. In the present study, we analyze the characteristics of the small caliber axons in Ten-4 -/- mice with several different ages.We first performed an immunohistochemical analysis of neurofilament (NF) and SMI-32, a marker for axon degeneration, in the spinal cords of 1-year-old (1y) mice. We found diffused staining of NF and increased signal of SMI-32 in Ten-4 -/- CST and FG, compared with the areas of wild-type (WT) mice. In addition, activation of microglia and astrocytes was observed in the Ten-4 -/- CST and FG tissues. We next carried out the same immunohistochemical experiment using the spinal cord tissues of 7-week-old (7w) and 7-day-old (7d) mice. As a result, similar but milder defects in the marker staining were detected in 7w mouse CST and FG tissues and there were no differences between WT and Ten-4 -/- spinal cords of 7d mice. These results indicated that axon degeneration occurred after the myelination defect, which was initiated around a week after birth, in the CST and FG of Ten-4 -/- mice. We further performed an electron microscopy analysis of 1y Ten-4 -/- mouse tissues and unexpectedly found that small diameter axons still existed in the CST and FG whereas they were not myelinated. The small axons tightly contacted between them in the Ten-4 -/- CST and FG, which increased the density of the axons in comparison with WT. In order to identify the proteins that promoted survival of the small caliber axons, we collected the dorsal column tissues from 1y WT and Ten-4 -/- mice and tested a shotgun-mass spectrometry analysis. From the comprehensive experiment, we obtained three proteins: a cell adhesion molecule, a molecular chaperone, and an enzyme in energy metabolism. In vitro functional analysis using specific activators or inhibitors revealed that these proteins regulated the maintenance of axons. These proteins may act as a survival factor in the unmyelinated small axons and be useful for the development of therapeutic reagents for the related diseases. | | 2022年7月2日 17:55～18:10 沖縄コンベンションセンター 会議場B2 第5会場
3O05e2-04
Rnd2によるミエリン形成過程の制御
Rnd2 regulates myelination by oligodendrocytes depending on myelinating period
*宮本 幸(1,2)、鳥居 知宏(3)、寺尾 美穂(4)、高田 修治(4)、加藤 裕教(5)、山内 淳司(2)
1. 国立成育医療研究センター 薬剤治療研究部、2. 東京薬科大学 生命科学部 分子神経科学研究室、3. 同志社大学 脳科学研究科、4. 国立成育医療研究センター システム発生・再生医学研究部、5. 京都大学 大学院生命科学研究科
*Yuki Miyamoto(1,2), Tomohiro Torii(3), Miho Terao(4), Shuji Takada(4), Hironori Katoh(5), Junji Yamauchi(2)
1. Department of Pharmacology, National Research Institute for Child Health and Development, 2. Laboratory of Molecular Neuroscience and Neurology, Tokyo University of Pharmacy and Life Sciences, 3. Graduate School of Brain Science, Doshisha University, 4. Department of Systems BioMedicine, National Research Institute for Child Health and Development, 5. Graduate School of Pharmaceutical Sciences, Kyoto University
Keyword: oligodendrocytes, myelination, small GTPases
In the central nervous system, oligodendrocyte precursor cells differentiate into oligodendrocytes to wrap their plasma membranes around neuronal axons, generating mature neural networks with myelin sheaths in spatial and temporal patterns. Mature myelin sheaths protect axons from various external stresses, including physical and physiological stresses, and insulate them to increase nerve conduction velocity. Although we know of various extrinsic and intrinsic cues such as growth factors, cell adhesion molecules, and protein kinases that mediate cellular morphology and gene expression, thereby regulating the spatial and temporal patterns of oligodendrocyte myelination, the overall picture of the myelination mechanism remains to be thoroughly clarified. Here, we describe the biphasic roles of Rnd2, an atypical branch of the Rho family GTPase, in oligodendrocyte myelination during development in mice. Compared with littermate controls, oligodendrocyte-specific Rnd2 knockout mice exhibit decreased myelin thickness at the onset of myelination whereas the knockout does increased thickness in the later period. Rho kinase and its substrate Mbs, the signaling unit that negatively regulates oligodendrocyte myelination, are phosphorylated at the onset of myelination, while their smaller proportions are phosphorylated in the later period. In addition, we confirm the biphasic role of Rnd2 through experiments with oligodendrocyte-specific Rnd2 transgenic mice. Therefore, we conclude that Rnd2 positively regulates myelination in the early myelinating period and negatively regulates myelination in the later period, demonstrating the presence of a unique modulator that plays different roles depending on the myelination period. | |
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