TOP ＞ Symposia

Symposia Next generation symposium by alumni of the Educational Seminars for Young Researchers ①【mechanisms and molecules】／若手育成セミナー出身者による次世代シンポジウム①【メカニズム・分子】 1S9-1 Decoding the brain development and neurodevelopmental disorders from the molecules Noriyoshi Usui1,2,3，Genevieve Konopka3，Hideo Matsuzaki1,2 1Division of Development of Mental Functions, Research Center for Child Mental Development, University of Fukui，2Division of Developmental Higher Brain Functions, Department of Child Development, United Graduate School of Child Development, Osaka University, Kanazawa University, Hamamatsu University School of Medicine, Chiba University and University of Fukui，3Department of Neuroscience, University of Texas Southwestern Medical Center The evolution of the human brain has led to an increased vulnerability to both neurodevelopmental and psychiatric disorders such as autism and schizophrenia. These disorders include phenotypes such as dysfunction in language and communication. It is therefore interesting that the implementation of spoken language in humans is perhaps the one of unique evolved characteristic of humans compared to other primates. However, while the molecular mechanisms underlying higher brain functions circuitry such as creativity, cognition and language in humans have likely expanded upon evolutionarily conserved circuitry most of these mechanisms and circuitry remain unknown. We are taking several approaches to identify the genes and molecular pathways important for both the evolution of these brain phenotypes as well as how they are disrupted in neurodevelpmental disorders. Here we show and discuss our latest findings of a single gene FOXP1 as an example how we can apply to the studies of brain development and neurodevelopmental disorders by focusing on the molecules. 1S9-2 Glia-mediated ischemic tolerance Yuri Hirayama1,2，Schuichi Koizumi1 1Dept. Neuropharmacol., Interdisciplinary Grad. Sch. Med., Univ. Yamanashi，2Dept. Pharmacy, Univ. Yamanashi Hospital Brain ischemic tolerance is an endogenous neuroprotective mechanism, whereby an experience of non-lethal ischemic episode (preconditioning; PC) produces resilience to subsequent lethal ischemia. We previously showed that PC caused activation of astrocytes and a subsequent upregulation of P2X7 receptors, activation of which resulted in ischemic tolerance via upregulation of HIF-1α in astrocytes. P2X7 receptor is expressed in resting microglia and is upregulated upon stimulation with PC. However, such microglial P2X7 receptor was not involved in ischemic tolerance. Here, we show that astrocytes have a unique mechanism of P2X7 receptor activation by PC, thereby leading to ischemic tolerance. Firstly, using a MCAO model of mice combined with microdialysis, we measured the extracellular ATP levels after PC. Although P2X7 receptor requires relatively higher extracellular ATP concentrations for its activation, the PC-evoked increase in ATP was not enough to activate P2X7 receptor. It has been reported that NAD at lower ATP concentration, which is released in response to ischemia, could activate P2X7 receptor via ART2-catalyzed ADP-ribosylation. Thus, secondly, we tested effect of NAD on astrocytic P2X7 receptors, and found that NAD increased HIF-1α in WT astrocytes but not in P2X7 receptor-deficient astrocytes in vitro. We also analyzed expression of ART2 in glial cells, and found that ART2 is expressed and upregulated by PC in astrocytes, but not in microglia. Taken together, our findings suggest that thanks to expression and upregulation of ART2, astrocytes could activate P2X7 receptors by their unique mechanisms, i.e., NAD/ART2/P2X7 signal pathways. This would allow astrocytes to induce ischemic tolerance without increasing higher extracellular ATP concentration by PC. 1S9-3 Discovery of Long-Range Inhibitory Signaling to Ensure Single Axon Formation Tetsuya Takano，Kozo Kaibuchi Dept Cell Pharmacology, Nagoya Univ Grad Sch Medicine, A long-standing question in neurodevelopment is how neurons develop a single axon and multiple dendrites from common immature neurites. Long-range inhibitory signaling from the growing axon is hypothesized to prevent outgrowth of other immature neurites and to differentiate them into dendrites, but the existence and nature of this inhibitory signaling remains unknown. Here, we demonstrate that axonal growth triggered by neurotrophin-3 (NT-3) remotely inhibits neurite outgrowth through long-range Ca2+ waves, which are delivered from the growing axon to the cell body. These Ca2+ waves increase RhoA activity in the cell body through calcium/calmodulin-dependent protein kinase I (CaMKI). Optogenetic control of Rho-kinase combined with computational modeling reveals that active Rho-kinase diffuses to growing other immature neurites and inhibits their outgrowth. Mechanistically, CaMKI phosphorylates a RhoA-specific GEF, GEF-H1, whose phosphorylation enhances its GEF activity. Thus, our results reveal that long-range inhibitory signaling mediated by Ca2+ waves is responsible for neuronal polarization. 1S9-4 Functional analyses of a novel mitochondrial fusion inhibitor MiFI in Pakinson’s disease models. Naoki Inoue1,2，Sae Ogura1，Norihito Shintani1，Hitoshi Hashimoto1,3,4 1Lab. Mol. Neuropharmacol., Grad. Sch. Pharmaceut. Sci., Osaka Univ.，2IPBS, Inst. for Academic Initiative, Osaka Univ.，3United Grad. Sch. Child Dev., Osaka Univ.，4Inst. Datability Sci., Osaka Univ. Parkinson’s disease (PD) is the most common motor system disorder due to the specific loss of the nigrostriatal dopaminergic neurons. Although the etiology of PD remains elusive, evidences for mitochondrial dysfunction and excessive generation of reactive oxygen species (ROS) have been increasingly convincing in both of the toxin and genetic PD models. For instance, inhibitors of mitochondrial respiration such as rotenone and 1-methyl-4-tetramethyl-p-phenylenediamine (MPTP) are well known to produce parkinsonian behavior with ROS-related striatal dopamine deficiency. Recent studies have also shown that PD-linked genetic mutations decrease the mitochondrial respiration, which propose mitochondrial dynamics, as a potential therapeutic target for PD. Mitochondria are highly dynamic organelles, and their function as well as morphology are properly regulated by fusion-fission cycles. However, its roles in the dopaminergic neurodegeneration remains poorly understood. We recently identified a novel 13-kDa protein down-regulated in pancreatic islets exposed to oxidative stress, and characterized it as a novel mitochondrial fusion inhibitor (MiFI). Here, we present our in vitro and in vivo data indicating the possible relation between MiFI and PD. The effects of lentiviral MiFI overexpression and suppression on the rotenone-induced cytotoxity were evaluated in dopaminergic SH-SY5Y cells. Phenotypic changes of MiFI knockout mice generated by CRISPR/Cas9 system were assessed with the MPTP-induced acute PD model. Our current results unravel the molecular pathogenesis of PD. Further analyses of MiFI function will identify the molecular basis of mitochondrial dynamics that contributes to drug discovery for PD.