一般口演
神経発生とグリア発生 / シナプス形成と活動依存的発達
Neurogenesis and Gliogenesis / Synaptogenesis and Activity-Dependent Development
座長：宮田 卓樹（名古屋大学） |
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| 2022年7月2日 14:00～14:15 沖縄コンベンションセンター 会議場B3・4 第6会場
3O06a1-01
自閉症感受性遺伝子AUTS2はマウス大脳皮質において上層神経細胞の産生に関与する
AUTS2 is required for the production of upper-layer neurons in mouse cerebral cortex
*嶋岡 可純(1)、堀 啓(1)、井上 由紀子(1)、郷 康弘(2)、阿部 学(3)、崎村 建司(3)、井上 高良(1)、星野 幹雄(1)
1. 国立精神・神経セ・神経研・病態生化学、2. 生理研・発達生理認知行動発達、3. 新潟大・脳研・基礎神経科学細胞神経生物
*Kazumi Shimaoka(1), Kei Hori(1), Yukiko U Inoue(1), Yasuhiro Go(2), Manabu Abe(3), Kenji Sakimura(3), Takayoshi Inoue(1), Mikio Hoshino(1)
1. Dept. of Biochem. & Cell. Biol., NCNP, Tokyo, 2. Dept. of Brain Sci., Center of Novel Sci. Initiative, NIPS, Okazaki, Aichi, 3. Dept. of Cell. Neurobiol., BRI, Univ. of Niigata
Keyword: Neurogenesis, Upper-layer neuron, intermediate progenitor
Autism susceptibility candidate 2 (AUTS2) has been implicated as the gene associated with numerous psychiatric disorders such as autism spectrum disorders (ASDs), intellectual disabilities (ID) and schizophrenia. In mouse developing CNS, AUTS2 is highly expressed at several brain regions responsible for the higher brain functions such as cerebral cortex and hippocampus. We have previously demonstrated that cytoplasmic AUTS2 regulates the neuronal migration and neurite formation in the developing cerebral cortex. Furthermore, nuclear AUTS2 has been reported to be involved in the transcriptional regulation of multiple genes for neural development by interacting with the Polycomb group protein complex 1 (PRC1). However, there remain many questions about the physiological roles for AUTS2 in the brain development. In this study, we investigated the function of AUTS2 in the cerebral corticogenesis and found that loss of Auts2 leads to the reduction of upper-layer neurons in the cerebral cortex. Moreover, EdU pulse-labeling experiments exhibited that the number of Cux1-positive upper-layer neurons was significantly reduced in the Auts2 mutant mice. Immunohistochemical analysis showed that the number of neural progenitor cells at the ventricular zone and subventricular zone was not altered between wild-type (WT) and Auts2 mutant cortices. Intriguingly, however, the cell cycle length of the intermediate progenitor cells (IPCs) was significantly prolonged in the Auts2 mutants compared to WT mice at embryonic day (E) 15.5, suggesting that the productivity of upper-layer neurons from IPCs was decreased in Auts2 mutant brains. We further performed RNA-seq analysis using IPC-derived RNA samples and identified multiple genes related to neural development that are differentially expressed in Auts2 mutant IPCs. Gene Ontology (GO) analysis revealed that the upregulated genes in Auts2 mutant IPCs were implicated as neural development such as “nervous system development”, “cell differentiation” and “negative regulation of cell proliferation”. Taken together, these results suggest that AUTS2 plays a key role for the cell cycle progression of IPCs and production of late-born neuron by regulating the expression of the genes for neuronal differentiation and/or proliferation of IPCs. | | 2022年7月2日 14:15～14:30 沖縄コンベンションセンター 会議場B3・4 第6会場
3O06a1-02
カドヘリン-6は大脳皮質形成においてニューロン移動を制御する
Cadherin-6 regulates neuronal migration during neocortical development
*廣田 ゆき(1)、齋藤 里香穂(1)、佐野 ひとみ(1,2)、仲嶋 一範(1)
1. 慶應義塾大学医学部解剖学、2. システム・バイオロジー研究機構
*Yuki Hirota(1), Rikaho Saito(1), Hitomi Sano(1,2), Kazunori Nakajima(1)
1. Dept Anat, Keio Univ Sch of Med, Tokyo, Japan, 2. The Systems Biol Inst, Tokyo, Japan
Keyword: CEREBRAL CORTEX, NEURONAL MIGRATION, CADHERIN
Neurons in the neocortex, which greatly develops especially in higher mammals, compose a 6-layered structure parallel to the brain surface. During neocortical development, most of the excitatory neurons are born in the ventricular zone and subventricular zone and migrate radially toward the brain surface. Upon arriving near the outermost part of the cortical plate (CP), they finally migrate in the terminal translocation mode, in which neurons shorten their leading processes while maintaining their tip in the marginal zone (MZ) to pull up their cell bodies to just beneath the MZ. Neurons stop migrating when they reach just beneath the MZ and form a CP in a so-called “inside-out” pattern, that is, the newly arriving neurons pass through their predecessor neurons to settle in the most superficial position in the CP. These neuronal migration and birthdate-dependent positioning (layer formation) are highly regulated by multiple signaling cascades, including the cell adhesion molecules. Cadherins, a large family of cell adhesion molecules, play important roles in cell migration, cell sorting and tissue separation by forming specific homophilic and heterophilic adhesion. Various cadherins are expressed in the developing brain, but in what aspect of development each cadherin is involved remains poorly understood. We searched for the cadherins expressed in migrating neurons in the developing neocortex using scRNA-seq databases and an atlas of mRNA expression in the brain. We then investigated their expression patterns in the developing neocortex in detail using fluorescent in situ HCR and focused on the Cdh6, which is expressed in the neurons migrating in the intermediate zone (IZ) and CP. The function of Cdh6 on migrating neurons was evaluated via RNA interference, and the results indicated that the knockdown (KD) of Cdh6 expression impaired neuronal migration in the IZ. Cdh6 is known to bind to integrin through the arginine-glycine-aspartic acid (RGD) motif and controls integrin-mediated adhesion in some cancer cells. Rescue experiments showed that migration defects caused by Cdh6 KD was restored by the expression of a KD-resistant form of wild-type Cdh6, but not by Cdh6 with a mutated RGD motif. These results suggest that Cdh6 controls the radial migration of neurons via interaction with integrins. | | 2022年7月2日 14:30～14:45 沖縄コンベンションセンター 会議場B3・4 第6会場
3O06a1-03
脳室内腔マクロファージが一部のミクログリアの供給源になる可能性
The possobility that border-associated macrophage in the ventricle can be a source of subpopulation of microglia
*服部 祐季(1)
1. 名古屋大学
*Yuki Hattori(1)
1. Nagoya University
Keyword: MICROGLIA, MACROPHAGE, DEVELOPING BRAIN, MIGRATION
Microglia, the resident immune cells of the central nervous system, have multiple functions in the embryonic brain. Although microglia are a scarce population during the embryonic stage, these cells can extensively survey the brain primordium and associate with surrounding neural lineage cells. Thus, these cells perform various functions, such as promoting differentiation of neural progenitors and modulating the wiring and positioning of neurons. Previous fate-mapping studies revealed that microglia originate from early erythromyeloid progenitors (EMPs) in the extraembryonic yolk sac at E7-8 in the developing mouse brain. These cells invade the CNS and colonize the cerebral parenchyma at E9 before blood-brain barrier formation. Once microglia are seeded in the brain parenchyma, these cells expand their population through migration and proliferation until the postnatal stage. On the other hand, border-associated macrophages (BAMs), the cells positioned in the ventricular lumen, meninges and choroid plexus, are derived from EMPs in the yolk sac as same as microglia. These two cell types exhibit different gene expression patterns and function at the specific region respectively. A recent study reported that the fate of these cells is determined when they are still present in the yolk sac during the early embryonic stage. However, our preliminary data raised the possibility that BAMs have a plasticity and transform into microglia. We found that almost all of the cells positive for CX3CR1, a common marker for microglia and macrophage, in the pallium were P2RY12+CD206low(microglia-like cells) at embryonic day (E) 14, whereas some P2RY12-CD206highcells (BAM-like cells) were distributed in the brain parenchyma at E12 and E13. Moreover, slice culture-based live imaging and in vivo observation using two-photon microscopy of CX3CR1-GFP+ cells showed that intraventricular BAMs, which were attached to the ventricular surface, frequently entered the cerebral parenchyma at E12. This infiltration was rarely observed after E13. These results suggest that BAMs, which enter the brain parenchyma from the ventricle, might transform into microglia by the environmental signals from the surrounding cells in the early embryonic stage. In this presentation, I would like to discuss these possibilities and the molecular mechanism underlying the entry of BAMs into the pallium. | | 2022年7月2日 14:45～15:00 沖縄コンベンションセンター 会議場B3・4 第6会場
3O06a1-04
臨界期アストロサイトは、ミクログリアによる貪食を制御することで大脳皮質神経回路を形成する
Astrocytes tune microglial engulfment of inhibitory synapses during postnatal development, which fates a lifelong cortical circuits.
*檀上 洋右(1,2)、篠﨑 陽一(1,2)、出羽 健一(3)、Kenji Kobayashi(1,2)、瀬川 高弘(4)、繁冨 英治(1,2)、小泉 修一(1,2)
1. 山梨大・院医・薬理学、2. 山梨GLIAセンター、3. グリア神経回路動態研究・理研、4. 山梨大・院医・総合分析
*Yosuke Danjo(1,2), Youichi Shinozaki(1,2), Ken-Ichi Dewa(3), Kenji Kobayashi(1,2), Takahiro Segawa(4), Eiji Shigetomi(1,2), Schuichi Koizumi(1,2)
1. Dept Neuropharmacol, Interdiscip Grad Sch Med, Univ Yamanashi, Yamanashi, Japan, 2. Yamanashi GLIA Center, Univ Yamanashi, Yamanashi, Japan, 3. Glia-Neuron Circuit Dynamics, RIKEN Center for Brain Science, Saitama, Japan, 4. Cent Life Sci Res., Univ. Yamanashi, Yamanashi, Japan
Keyword: Astrocyte, Microglia, Engulfment, Synapse
Glial cells are essential for the organization of synaptic connections and healthy brain development. They control the excitatory / inhibitory synaptic balance and assemble neural circuity by synaptic formation and elimination. We have recently revealed that astrocytes form excitatory synapses in the adult injured brain through mGluR5 signaling. However, in the healthy brain, astrocytic mGluR5 is expressed in the only limited time-window of the postnatal developmental stage. Therefore, we investigated whether and how astrocytic mGluR5 destines the subsequent synaptic assembly using astrocyte-specific mGluR5 KO mice (astro-mGluR5 cKO). Unexpectedly, the number of excitatory synapses did not alter much in astro-mGluR5 cKO, instead, the number of inhibitory synapses decreased significantly in astro-mGluR5 cKO throughout ages. Interestingly, this decrease was due to phagocytosis by microglia, not by astrocytes. In fact, microglia frequently engulfed inhibitory synaptic elements in the critical period in astro-mGluR5 cKO. Although astrocytic mGluR5 expression was a transient event limited in the critical period, its deficient affected the rest of the life, and in fact, behavioral dysfunction was observed in adult astro-mGluR5 cKO mice. Next, we explored mechanisms underlying astrocytic mGluR5 deficiency-mediated microglial engulfment. We screened several astrocyte-related molecules and focused on IL7 as a candidate for such a molecule, because it dramatically decreased in astro-mGluR5 cKO. In fact, treatment of microglia with IL7 decreased expression of several engulfment-related genes. Hence, we conclude that astrocytes organize inhibitory network in the critical period by tuning microglial phagocytic activity via IL7-mediated mechanisms. It should be noted that although mGluR5 is only transiently expressed in astrocytes in the critical period, its function greatly affects the inhibitory neuronal networks throughout life. | |
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