一般（口演）

一般（口演）グリア、ミエリン2

1B-一般2-1 エピジェネティック機構を介した受容体型チロシンキナーゼRor2の発現誘導によるアストロサイトの細胞周期制御遠藤光晴，小林千穂，グリジャハンオブリカスム，南康博神戸大学大学院医学研究科細胞生理学グリア細胞のひとつであるアストロサイトは、脳全体に分布しており、脳機能に重要な役割を担っている。通常アストロサイトは細胞増殖を停止した状態にあるが、脳損傷時には増殖を再開することで損傷後の組織修復に関わることが知られている。しかしながら、アストロサイトの増殖を制御する分子機構については未だ不明な点が多い。我々は、発生過程における組織形成に重要な役割を担うRorファミリー受容体型チロシンキナーゼRor2が、発生期の神経幹細胞に高発現しており、その未分化性の維持に働くことを明らかにしてきた。発生過程と比較して、成獣マウス脳内ではRor2の発現はごく僅かであるが、脳損傷後のアストロサイトではその発現が上昇することを見出した。培養アストロサイトを用いた解析から、Ror2はアストロサイトの増殖促進活性をもつbasic fibroblast growth factor（bFGF）刺激により発現誘導されることが明らかになった。Ror2欠損マウス由来のアストロサイトでは、bFGF刺激による細胞周期のS期への進展が抑制されたことから、Ror2の発現誘導はアストロサイトの細胞周期進行に必要であると考えられる。興味深いことに、bFGFによるRor2の発現誘導は、アストロサイト全集団のうち一部でのみ認められ、これらの細胞が主にS期へと進行することが示された。一方、ヒストン脱アセチル化酵素阻害剤で処理すると、より多くのアストロサイトでbFGF依存的なRor2の発現誘導が認められたことから、Ror2遺伝子の転写活性はエピジェネティック機構により制御されており、活性化状態の細胞でのみbFGF刺激によりRor2が発現誘導され、細胞周期の進展が促進されると考えられる。実際、Ror2を構成的に発現させたアストロサイトではbFGF刺激に応答してS期へと進行する細胞の割合が増加していた。損傷を受けた脳内のアストロサイトでも、同様の機序によりRor2の発現が誘導され、その結果、細胞周期の進展が促進されることが予想され、この点についても議論したい。		1B-一般2-2 Functional role of activated astrocytes for blood-brain barrier breakdown after the brain injury 池島（片岡）宏子^1,2，古川元子²，乾さやか²，今村愛枝²，安井正人² ¹早稲田大学・理工学術院，²慶應義塾大学・医学部・薬理学教室 Astrocytes and microglial cells become active when the brain had injury or inflammation；however, the biological significance is not yet well known. For the brain injury model, we used stab wound injury to the mouse cerebral cortex to examine the functional role of reactive astrocytes and microglia. Stab wound injury induces blood-brain barrier（BBB）breakdown, but it will be recovered in a week. We have previously reported that extracellular matrix molecule tenascin-C（TN-C）might be concerned in activation of astrocytes and have the functional role for recovery from BBB breakdown. In this study, to know the relationship between astrocyte activation and BBB recovery from breakdown after the brain injury, we analyzed IgG leakage using immunofluorescent staining with anti-mouse IgG antibody for evaluation of recovery from BBB breakdown. IgG leakage was mostly high at 1 day after the stab wound injury, but diminished almost by 7 days after that. We used bromo-deoxy uridine（BrdU）incorporation with drinking water for mice to analyze the proliferation rate of astrocytes using anti-BrdU antibody for the brain sections. At the same time, anti-GFAP antibody was used to examine activation of astrocytes by co-immunostaining. The number of GFAP-positive astrocyte was mostly high at day after 3 of injury, and then the activity was decreased by day after 7. RT-qPCR method was performed to study the expression level of the genes related to the BBB integrity and astrocyte activation, and found that most of the genes concerned in BBB integrity were down regulated just after the BBB breakdown, while they recovered to basal level within 7 days. These results suggested that there are some correlation between astrocyte activation and the BBB recovery from breakdown caused by stab wound brain injury.

1B-一般2-3 The role of mechanosensors in oligodendrocyte morphogenesis and maturation 清水健史^1,2，長内康幸¹，田中謙二³，阿部学⁴，夏目里恵⁴，崎村建司⁴，池中一裕^1,2 ¹生理研・分子神経生理，²総研大・生理科学，³慶応大・医学部・精神神経科学，⁴新潟大・脳研・細胞神経生物 Oligodendrocytes（OLs）are glial cells that myelinate neuronal axons in the central nervous system（CNS）. Recent studies have shown that mechanical environment influences behavior and function of various cell types. Externally applied mechanical stimulation can be transduced to intracellular biochemical signals through focal adhesion-related mechanosensors and activate intracellular mechanotransducers. However, molecular mechanisms underlying the mechanical regulation of postnatal OLs remain unclear. We found that knock-down of mechanosensors in OLs affected their morphology and reduced the interactions between OLs and dorsal root ganglion（DRG）neurons in a co-culture system. When oligodendrocyte precursor cells seeded on a silicon chamber were mechanically extended by stretch machine, or shear stress was applied to OLs, these mechanical stresses modulate OL morphology via mechanosensor activity. To investigate whether mechanosensors function in postnatal OLs in vivo, we newly produced mechanosensor knock-in mice using the previously reported FAST system. OL lineage-specific misexpression of the mechanosensor in vivo widely affected OL maturation in the CNS white matter. These results suggest that mechanosensors function in OL morphogenesis and maturation. Mechanical regulation of myelination is a new concept and might provide us with a novel target for the treatment of demyelinating diseases.		1B-一般2-4 Focal accumulation of type 1 inositol 1,4,5-trisphosohate receptor triggers Purkinje axonal swellings in paranodal axo-glial junctional deficient mice. 石橋智子¹，高橋早紀¹，水野珠璃¹，御子柴克彦²，馬場広子¹ ¹東京薬科大学薬学部機能形態学，²理化学研究所脳科学総合研究センター In vertebrates, myelinated axons exhibit a type of remarkably specialized structures that are called paranodal axo-glial junctions（PNJs）. PNJs are essential in the formation and maintenance of clusters of axonal membrane proteins such as Na⁺ and K⁺ channels. There is increasing evidence that myelin sheaths―especially PNJs―contribute to several aspect of axonal homeostasis. Previously we reported that cerebroside sulfotransferase（CST；a sulfatide synthetic enzyme）deficient mice, which partially lack PNJs, show Purkinje axonal swellings, and that type 1 inositol 1,4,5-trisphosphate receptor（IP₃R1）-positive focal accumulations are the earliest finding in these swellings. Massive stack formation of ER membranes is sometimes observed in Purkinje axons from CST-deficient mice, which is similar to findings in IP₃R1 overexpression in vitro. To examine whether IP₃R1 triggers the Purkinje axonal swellings in mutant mice, we investigated cerebella from CST^-/-/IP₃R1^+/- mice. At 18 days of age, calbindin/IP₃R1-positive focal small swellings were already observed in CST^-/-/IP₃R1^+/+ axons. However, there were clearly less axonal swellings in CST^-/-/IP₃R1^+/- mice（compared to CST^-/-/IP₃R1^+/+ mice）, at least until 4 or 5 months of age. CST^-/-/IP₃R1^+/+ mice did not show any other axonal alterations such as disruption of initial segments except for a partial lack of PNJs. These results suggest that the focal accumulation of IP₃R1 triggers Purkinje axonal swellings in PNJ-deficient mice.

1B-一般2-5 Neuroprotective effect of nicotine by inhibiting microglial H⁺ currents via interactions with α7AChR 野田百美，小林亜衣九州大院・薬・病態生理学 Alpha 7 subunits of nicotinic acetylcholine receptors（nAChRs）are expressed in microglia and are involved in the suppression of neuroinflammation. Over the past decade, many reports show beneficial effects of nicotine, though little is known about the mechanism. Here we show that nicotine inhibits lipopolysaccharide（LPS）-induced proton（H⁺）currents and morphological change by using primary cultured microglia. The H⁺ channel currents were measured by whole-cell patch clamp method under voltage-clamp condition. Increased H⁺ current in activated microglia was attenuated by blocking NADPH oxidase. The inhibitory effect of nicotine was due to the activation of α7 nAChR, not a direct action on the H⁺ channels, because the effects of nicotine was cancelled by α7 nAChR antagonists. Neurotoxic effect of LPS-activated microglia due to inflammatory cytokines was also attenuated by pre-treatment of microglia with nictotine. These results suggest that α7 nAChRs in microglia may be a therapeutic target in neuroinflammatory diseases.