神経回路の構築：発生学から再生戦略へ Neural circuit formation: From developmental biology to repair strategy
S1-3-1-1 The role of lysophosphatidylglucoside and its receptor in spinal cord axon tract formation ○Adam T. Guy1, Hiroyuki Kamiguchi1 Lab. for Neuronal Growth Mechanisms, RIKEN Brain Science Institute1 The central nervous system (CNS) is highly enriched in lipids yet classical axon guidance molecules are proteins or their derivatives. We investigated whether certain lipid species can act as intercellular signalling molecules in the developing CNS. We have found that the lysophospholipid lyso-phosphatidylglucoside (LPG), a hydrolytic derivative of the membrane lipid phosphatidyl-β-D-glucoside, is an axon guidance molecule in the spinal cord. In vitro LPG exerted a strong chemorepulsive effect specific to nociceptive sensory afferent axons. Attenuating LPG signalling in vivo using a function-blocking antibody disrupted the longitudinal patterning of nociceptive sensory axons, causing them to spread more dorsally to a domain in which usually proprioceptive axons predominate. We subsequently discovered that the chemorepulsive activity of LPG is mediated by its specific binding to a G protein-coupled receptor we have tentatively named LPGR. Genetic deletion of the LPGR in mice causes nociceptive sensory afferent pathfinding errors in the spinal cord during development. In summary, LPG/LPGR-signalling is a novel axon guidance mechanism required for the correct projection and patterning of nociceptive sensory afferents in developing spinal cord. Given their diversity and abundance in the central nervous system, it is likely other intercellular signals mediated by lipids exist that remain to be discovered.	S1-3-1-2 皮質脊髄路ニューロンの生存を制御するミクログリア由来因子 Layer V cortical neurons require microglial support for survival during postnatal development ○山下俊英1, 藤田幸1, 上野将紀1 ○Toshihide Yamashita1, Yuki Fujita1, Masaki Ueno1 大阪大学大学院医学系研究科分子神経学教室1 Dept. of Molecular Neuroscinece, Grad. Sch. of Med., Osaka University1 Neurons require trophic support during neural circuit formation; however, it remains unclear how the cellular milieu contributes to neuronal survival. Here, we demonstrate that layer V cortical neurons require support from microglia for survival during postnatal development. Specifically, we found that microglia accumulated close to the subcerebral and callosal projection axons in the postnatal brain. Inactivation of microglia by minocycline treatment or transient ablation of microglia in CD11b-DTR transgenic mice led to increased apoptosis, specifically in layer V subcerebral and callosal projection neurons. CX3CR1 in microglia was required for the survival of layer V neurons. Microglia consistently promoted the survival of cortical neurons in vitro. In addition, we identified microglia-derived IGF1 as a trophic factor that maintained neuronal survival. Our results highlighted a novel neuron-glia interaction that was indispensable for network formation during a specific period in the developing brain.
S1-3-1-3 神経系の発生と再生における内在性Nogo受容体アンタゴニストLOTUSの機能 Function of an endogenous Nogo receptor antagonist LOTUS in developing and regenerating brains ○竹居光太郎1 ○Kohtaro Takei1 横浜市立大学医学部生命医科学部門1 Div. of Medical Life Scineces, Yokohama City Univ. School of Medicine1 Neural circuitry formation and functional recovery after injury depends on the molecular control of axonal projection during development and regeneration. By the functional screening, we identified lateral olfactory tract usher substance (LOTUS) and Nogo receptor-1 (NgR1) as a LOTUS-binding protein. NgR1 is well known as a receptor of myelin-derived axon growth inhibitors, such as Nogo, myelin glycoprotein (MAG) and oligodendrocyte myelin glycoprotein (Omgp), which prevent neural regeneration in the adult central nervous system. LOTUS suppresses binding of these NgR1 ligands to NgR1 and their ligands-induced axon growth inhibition.A defasciculated axon bundle and increased axon branching of LOT are observed in single mutants of lotus-deficient mice, whereas these phenotypes was rescued in double mutants of lotus- and ngr1-deficient mice. These findings suggest that endogenous antagonism of LOTUS to NgR1 plays a crucial role in axon bundling and branching of LOT in developing brain. On the other hand, we generated the animal model of spinal cord injury (SCI) in lotus-deficient mice and assessed the locomotor function, since LOTUS was expressed in the spinal cord. The lotus-deficient mice showed remarkably delayed recovery of the locomotor function compared with the wild type mice. LOTUS expression was remained similar level of intact spinal cord for about two weeks after SCI and then down-regulated when recovery is attenuated. These results suggest that endogenous LOTUS may contribute to a partial improvement of nerve regeneration after injury in rodents. Such antagonistic action of LOTUS to NgR1 provides new insight into neural development mechanisms and also therapeutic approaches for brain injury.	S1-3-1-4 神経発生と可塑性におけるコンドロイチン硫酸の機能 Roles of chondroitin sulfate in neural development and plasticity ○宮田真路1, 北川裕之1 ○Shinji Miyata1, Hiroshi Kitagawa1 神戸薬科大学生化学研究室1 Dept. of Biochemistry, Kobe Pharmaceutical University1 Cortical circuits are sensitive to experience during a critical period in early life. Plasticity is markedly reduced after the critical period, suggesting the presence of molecular brakes that limit plasticity in adult brain. Chondroitin sulfate (CS), a major component of the brain extracellular matrix, is reported to play a role in closing the critical period. Digestion of CS chains has shown to restore visual cortical plasticity in adult animals, but the underlying mechanisms remain unknown. CS chain is a linear polysaccharide consisting of repeating disaccharide units that can be substituted with sulfate groups at various positions, thereby producing characteristic sulfation patterns. Thus we hypothesized that sulfation patterns of CS chains regulate the critical period plasticity. Using transgenic mouse model overexpressing chondroitin 6-sulfotransferase-1, we found that a developmental increase in the 4-sulfation/6-sulfation (4S/6S) ratio of CS chains leads to the termination of the critical period in the mouse visual cortex. Condensation of CS-proteoglycans into perineuronal nets that enwrapped parvalbumin-expressing interneurons (PV-cells) was prevented by cell-autonomous overexpression of chondroitin 6-sulfation. Mechanistically, the increase in the 4S/6S ratio was required for accumulation of Otx2, a homeoprotein that activates development of PV-cells, and for functional maturation of electrophysiological properties of these cells. Furthermore, we suggest the occurrence of an Otx2-binding domain in CS chains that are enriched near synaptic contacts. Our study reveals a novel mechanism for the critical period plasticity, in which specific sulfation patterns of CS chains regulate the maturation of PV-cells through the incorporation of Otx2. Reference: Miyata, S. et. al. (2012) Nat. Neurosci. 15, 414-422.
S1-3-1-5 Absence of MHC1 or PirB improves recovery from stroke in mice ○Rona Giffard1, Jaimie Adelson2, George Barreto1, Lijun Xu1, Taeho Kim3, Barbara Brott3, Yibing Ouyang1, Thorsten Naserke3, Maja Djurisic3, Xiaoxing Xiong1, Carla Shatz2,3 Dept. of Anesthesia, Stanford University School of Medicine1, Dept Neurobiology, Stanford Univ2, Dept Biology, Stanford Univ3 Stroke is a leading cause of death and a major cause of chronic neurological disability worldwide. Developing a treatment to improve neurological recovery, rather than focus on acute injury, could help more stroke patients. PirB signaling is known to limit neuronal plasticity, so we tested whether its absence would facilitate recovery from stroke. PirB and its ligands, the major histocompatibility class I (MHCI) molecules, are important in immune system function, but also regulate brain plasticity. MHCI molecules are expressed on neurons, and mice lacking MHCI function show increased plasticity in development and adulthood, suggesting this could be a target in stroke. We performed middle cerebral artery occlusion (MCAO) on mice in which either the innate immune receptor PirB, or two of its ligands, H2-Kb and H2-Db were knocked out (KO), and wild type (WT) controls. PirB and ligands Kb and Db were elevated in neurons in wild type mice after MCAO. In KO mice we observed improved neurobehavioral recovery by rotarod and foot fault tests, and reduction in infarct size. We studied injury in isolated hippocampal slices to assess effects on injury in the absence of the immune system. We found significant neuronal preservation in slices from KO mice relative to WT. We then assessed corticospinal tract fibers originating from the undamaged motor cortex and terminating in the red nucleus of the damaged side. We observed both increased length and number of fibers in PirB KO compared to WT. These results demonstrate that PirB signaling is normally increased in the setting of stroke, and that eliminating PirB signaling improves neuronal survival and neurobehavioral function. That the improved function reflects increased plasticity is consistent with the observed increase of corticospinal tract fibers. This work suggests that PirB signaling is a possible new target to improve outcome following stroke, and it may be application to a broad range of stroke patients.

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