Language：Japanese   Publisher：The Japanese Association for the Study of Taste and Smell  

嗅球の僧帽細胞はそれぞれ1 本の主樹状突起を1 つの糸球体へと接続し、1 種類の嗅覚受容体由来の興奮性入力を受け取る。僧帽細胞は、生後直後には複数の主樹状突起を有するが、その後の発達期に樹状突起の刈り込みを行うこ
とで単一の主樹状突起を確立する。近年、我々の研究によって、この樹状突起刈り込みが自発神経活動に依存して生じること、この過程には「シナプス競合」が関わっており、入力を受けたシナプスを「局所保護」しつつ、それ以外のシナプスを刈り込む「側方抑制」の仕組みによって単一の樹状突起が確立されることが明らかになった。

DOI： 10.18965/tasteandsmell.30.2_101

CiNii Research

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3389/fnana.2021.760063

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.celrep.2021.109276

Language：English   Publishing type：Research paper (scientific journal)  

The glomerular map in the olfactory bulb (OB) is the basis for odor recognition. Once established during development, the glomerular map is stably maintained throughout the life of an animal despite the continuous turnover of olfactory sensory neurons (OSNs). However, traumatic damage to OSN axons in the adult often leads to dysosmia, a qualitative and quantitative change in olfaction in humans. A mouse model of dysosmia has previously indicated that there is an altered glomerular map in the OB after the OSN axon injury; however, the underlying mechanisms that cause the map distortion remain unknown. In this study, we examined how the glomerular map is disturbed and how the odor information processing in the OB is affected in the dysosmia model mice. We found that the anterior-posterior coarse targeting of OSN axons is disrupted after OSN axon injury, while the local axon sorting mechanisms remained. We also found that the connectivity of mitral/tufted cell dendrites is reduced after injury, leading to attenuated odor responses in mitral/tufted cells. These results suggest that existing OSN axons are an essential scaffold for maintaining the integrity of the olfactory circuit, both OSN axons and mitral/tufted cell dendrites, in the adult.

DOI： 10.1523/ENEURO.0242-16.2016

Language：English   Publishing type：Research paper (scientific journal)  

Super-resolution imaging deep inside tissues has been challenging, as it is extremely sensitive to light scattering and spherical aberrations. Here, we report an optimized optical clearing agent for high-resolution fluorescence imaging (SeeDB2). SeeDB2 matches the refractive indices of fixed tissues to that of immersion oil (1.518), thus minimizing both light scattering and spherical aberrations. During the clearing process, fine morphology and fluorescent proteins were highly preserved. SeeDB2 enabled super-resolution microscopy of various tissue samples up to a depth of >100 μm, an order of magnitude deeper than previously possible under standard mounting conditions. Using this approach, we demonstrate accumulation of inhibitory synapses on spine heads in NMDA-receptor-deficient neurons. In the fly medulla, we found unexpected heterogeneity in axon bouton orientations among Mi1 neurons, a part of the motion detection circuitry. Thus, volumetric super-resolution microscopy of cleared tissues is a powerful strategy in connectomic studies at synaptic levels.

DOI： 10.1016/j.celrep.2016.02.057

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.21769/BioProtoc.1042

Language：English   Publishing type：Research paper (scientific journal)  

We report a water-based optical clearing agent, SeeDB, which clears fixed brain samples in a few days without quenching many types of fluorescent dyes, including fluorescent proteins and lipophilic neuronal tracers. Our method maintained a constant sample volume during the clearing procedure, an important factor for keeping cellular morphology intact, and facilitated the quantitative reconstruction of neuronal circuits. Combined with two-photon microscopy and an optimized objective lens, we were able to image the mouse brain from the dorsal to the ventral side. We used SeeDB to describe the near-complete wiring diagram of sister mitral cells associated with a common glomerulus in the mouse olfactory bulb. We found the diversity of dendrite wiring patterns among sister mitral cells, and our results provide an anatomical basis for non-redundant odor coding by these neurons. Our simple and efficient method is useful for imaging intact morphological architecture at large scales in both the adult and developing brains.

DOI： 10.1038/nn.3447

Language：English   Publishing type：Research paper (scientific journal)  

EphA2, a member of the Eph receptor family, is frequently overexpressed in a variety of human cancers, including breast cancers, and promotes cancer cell motility and invasion independently of its ligand ephrin stimulation. In this study, we identify Ephexin4 as a guanine nucleotide exchange factor (GEF) for RhoG that interacts with EphA2 in breast cancer cells, and knockdown and rescue experiments show that Ephexin4 acts downstream of EphA2 to promote ligand-independent breast cancer cell migration and invasion toward epidermal growth factor through activation of RhoG. The activation of RhoG recruits its effector ELMO2 and a Rac GEF Dock4 to form a complex with EphA2 at the tips of cortactinrich protrusions in migrating breast cancer cells. In addition, the Dock4-mediated Rac activation is required for breast cancer cell migration. Our findings reveal a novel link between EphA2 and Rac activation that contributes to the cell motility and invasiveness of breast cancer cells.

DOI： 10.1083/jcb.201005141

Language：English   Publishing type：Research paper (scientific journal)  

In early cortical development, neural progenitor cells (NPCs) expand their population in the ventricular zone (VZ), and produce neurons. Although a series of studies have revealed the process of neurogenesis, the molecular mechanisms regulating NPC proliferation are still largely unknown. Here we found that RhoG, a member of Rho family GTPases, was expressed in the VZ at early stages of cortical development. Expression of constitutively active RhoG promoted NPC proliferation and incorporation of bromodeoxyuridine (BrdU) in vitro, and the proportion of Ki67-positive cells in vivo. In contrast, knockdown of RhoG by RNA interference suppressed the proliferation, BrdU incorporation, and the proportion of Ki67-positive cells in NPCs. However, knockdown of RhoG did not affect differentiation and survival of NPC. The RhoG-induced promotion of BrdU incorporation required phosphatidylinositol 3-kinase (PI3K) activity but not the interaction with ELMO. Taken together, these results indicate that RhoG promotes NPC proliferation through PI3K in cortical development.

DOI： 10.1091/mbc.E09-03-0200

Language：English   Publishing type：Research paper (scientific journal)  

Plexins are receptors for axonal guidance molecules known as semaphorins. We recently reported that the semaphorin 4D (Sema4D) receptor, Plexin-B1, induces axonal growth cone collapse by functioning as an R-Ras GTPase activating protein (GAP). Here, we report that Plexin-B1 shows GAP activity for M-Ras, another member of the Ras family of GTPases. In cortical neurons, the expression of M-Ras was upregulated during dendritic development. Knockdown of endogenous M-Ras-but not R-Ras-reduced dendritic outgrowth and branching, whereas overexpression of constitutively active M-Ras, M-Ras(Q71L), enhanced dendritic outgrowth and branching. Sema4D suppressed M-Ras activity and reduced dendritic outgrowth and branching, but this reduction was blocked by M-Ras(Q71L). M-Ras(Q71L) stimulated extracellular signal-regulated kinase (ERK) activation, inducing dendrite growth, whereas Sema4D suppressed ERK activity and down-regulation of ERK was required for a Sema4D-induced reduction of dendrite growth. Thus, we conclude that Plexin-B1 is a dual functional GAP for R-Ras and M-Ras, remodelling axon and dendrite morphology, respectively.

DOI： 10.1038/embor.2009.63

Language：English   Publishing type：Research paper (scientific journal)  

Dendrite development is required for establishing proper neuronal connectivity. Rho-family small GTPases have been reported to play important roles in the regulation of dendritic growth and morphology. However, the molecular mechanisms that control the activities of Rho GTPases in developing dendrites are not well understood. In the present study we found Dock4, an activator of the small GTPase Rac, to have a role in regulating dendritic growth and branching in rat hippocampal neurons. Dock4 is highly expressed in the developing rat brain, predominantly in hippocampal neurons. In dissociated cultured hippocampal neurons, the expression of Dock4 protein is up-regulated after between 3 and 8 days in culture, when dendrites begin to grow. Knockdown of endogenous Dock4 results in reduced dendritic growth and branching. Conversely, overexpression of Dock4 with its binding partner ELMO2 enhances the numbers of dendrites and dendritic branches. These morphological effects elicited by Dock4 and ELMO2 require Rac activation and the C-terminal Crk-binding region of Dock4. Indeed, Dock4 forms a complex with ELMO2 and CrkII in hippocampal neurons. These findings demonstrate a new function of the Rac activator Dock4 in dendritic morphogenesis in hippocampal neurons.

DOI： 10.1002/jnr.21763

Language：English   Publishing type：Research paper (scientific journal)  

ELMO is an upstream regulator of the Rho family small GTPase Rac. We investigated the distributions of mRNAs of two subtypes of ELMO, ELMO1 and ELMO2, in the developing mouse brain. Both ELMO1 and ELMO2 mRNAs are widely distributed in the developing mouse brain, but they were expressed in different neuronal populations in the cerebral cortex, thalamus, and cerebellum. Thus, ELMO1 and ELMO2 may play different roles during brain development.

DOI： 10.1016/j.brainres.2005.12.085

Event date： 2020.1

Language：Japanese   Presentation type：Symposium, workshop panel (public)  

Venue：福岡市 (福岡国際会議場・福岡サンパレス ホテル＆ホール・マリンメッセ福岡)   Country：Japan  

Event date： 2023.11

Language：English   Presentation type：Oral presentation (general)  

Venue：岡山大学、岡山市   Country：Japan  

Event date： 2023.10 - 2023.11

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡国際会議場、福岡市   Country：Japan  

Event date： 2023.8 - 2023.4

Language：English  

Venue：仙台市　仙台国際センター   Country：Japan  

Event date： 2023.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：兵庫県神戸市   Country：Japan  

Event date： 2021.7 - 2022.7

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2020.9

Language：Japanese  

Venue：WEB開催   Country：Japan  

Event date： 2020.1

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：福岡市東区　(九州大学歯学部研究棟)   Country：Japan  

Event date： 2018.1

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：北九州市小倉北区 (北九州国際会議場)   Country：Japan  

Language：Japanese  

Language：Japanese  

Language：English  

Language：English  

Language：English  

DOI： 10.1101/2022.10.20.512984

Language：English  

DOI： 10.1101/2020.10.30.358861

Language：English  

DOI： 10.1101/625616

Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (scientific journal)