一般口演
シナプス形成と活動依存的発達 / 発達と進化のエピジェネティック制御など
Synaptogenesis and Activity-Dependent Development / Epigenetic Control of Development and Evolution
座長：水野 秀信（熊本大学） |
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| 2022年7月2日 15:00～15:15 沖縄コンベンションセンター 会議場B3・4 第6会場
3O06a2-01
マウス一次視覚野におけるfast-spiking抑制性細胞－錐体細胞間結合の発達
Development of the connections between fast-spiking interneurons and pyramidal neurons in mouse visual cortex
*山本 真理子(1,2)、岩里 琢治(3,4)、吉村 由美子(1,2)
1. 生理研視覚情報処理、2. 総研大院生命科学生理科学、3. 国立遺伝研神経回路構築、4. 総研大院生命科学遺伝学
*Mariko Yamamoto(1,2), Takuji Iwasato(3,4), Yumiko Yoshimura(1,2)
1. Div of Vis Info Proc, NIPS, Okazaki, Japan, 2. Dept Physiol Sci, SOKENDAI, Okazaki, Japan, 3. Lab of Mammalian Neural Circuits, NIG, Mishima, Japan, 4. Dept Genetics, SOKENDAI, Mishima, Japan
Keyword: inhibitory neurons, development, synaptic connections, cortex
Fast spiking (FS) inhibitory neurons in the neocortex are a major source of inhibition that controls the timing of activity of nearby pyramidal (Pyr) neurons. FS cells are often reciprocally connected with surrounding excitatory Pyr neurons. In addition, inhibitory connections originating from FS neurons are stronger in reciprocally connected pairs than one-way inhibitory connected pairs. This study investigated the development of synaptic connections between FS-Pyr neurons in the primary visual cortex. We performed dual whole-cell recordings from FS and Pyr cells in layer 2/3 of visual cortical slices. We used mice at postnatal 11-16 days (P11-16, around eye-opening) and P21-26. We found that the connection probability of both excitatory and inhibitory connections between FS and Pyr cells increased from P11 to P16, resulting in high reciprocity at P14-16. When both eyelids were sutured just before eye-opening until P14-16, the reciprocal pairs increased similar to non-sutured mice, suggesting that the connectivity was developed independently of visual experience. Afterward, the proportion of reciprocal pairs significantly decreased at P21-26, due to decreased excitatory connections. For analysis of synaptic strength, we focused on inhibitory connections. The amplitude of inhibitory postsynaptic currents (IPSCs) increased from P11 to P16, and this increase was maintained until P21-26. Interestingly, the amplitude was similar between reciprocal and one-way connected pairs around eye-opening, whereas that was significantly larger in reciprocal pairs than in one-way connected pairs at P21-26. We next studied the contribution of NMDA receptors (NMDARs) to the development of FS-Pyr neuron connections using P21-26 mice. A GluN1-flox mouse line was used to perform conditional knock-out (cKO) of GluN1, the essential subunit of NMDARs. Cre recombinase was driven by three different promoters in AAVs: CMV for the ubiquitous KO, CaMKIIα for the Pyr neuron-specific KO, and mDlx for the inhibitory neuron-specific KO. None of these cKO of GluN1 affected the connection probability in FS and Pyr neuron pairs. However, the difference in IPSCs amplitude between reciprocal and one-way connected pairs disappeared following CMV and mDlx dependent KO, but not CaMKIIα. Our results suggest that in FS-Pyr neuron pairs, the proportion of reciprocal connections is adjusted during development, and reciprocity-dependent potentiation of IPSCs occurs depending on NMDARs in FS neurons. | | 2022年7月2日 15:15～15:30 沖縄コンベンションセンター 会議場B3・4 第6会場
3O06a2-02
神経過活動は神経細胞の擬似的な有糸分裂期様への再進入と核構造の長期的な変化を誘導する
Neural hyperexcitation induces M-phase reentry and long-term changes in the nuclear structure of neurons.
*村野 友幸(1)、萩原 英雄(1)、加藤 薫(2,3,4)、波平 昌一(2)、宮川 剛(1)
1. 藤田医科大学総合医科学研究所、2. 産業技術総合研究所 バイオメディカル研究部門、3. 産業技術総合研究所 人工知能研究センター、4. 筑波大学 グローバル教育院 ヒューマニクス学位プログラム
*Tomoyuki Murano(1), Hideo Hagihara(1), Kaoru Katoh(2,3,4), Masakazu Namihira(2), Tsuyoshi Miyakawa(1)
1. Institute for Comprehensive Medical Science, Fujita Health University, 2. Biomedical Research Institute, National Institute of Advanced Industrial Science and Technology, 3. Artificial Intelligence Research Center, National Institute of Advanced Industrial Science and Technology, 4. Ph.D. Program in Humanics, School of Integrative and Global Majors, University of Tsukuba
Keyword: dentate gyrus, epigenetics, cell cycle reentry
Neural excitation induces dynamic changes in gene expression patterns and the three-dimensional structure of the genome. These changes are plastic in the normal adult brain, but they are in chronic abnormal states in the brains of patients with various neuropsychiatric disorders, such as schizophrenia and Alzheimer's disease. Neuronal hyperexcitation is one of the main etiological factors of these neuropsychiatric disorders and is believed to contribute to the chronic changes in gene expression and genomic structure of neurons, but it is not clear how they cause these changes. This study shows that hyperexcitation causes global changes in gene expression patterns and the genomic structure of neurons of the dentate gyrus. These changes were transient and reversible after three consecutive days of intermittent stimulation, while they persisted for more than two weeks after ten days of stimulation. Ten days of stimulation also induced abnormal nuclear structures in neurons resembling the M phase in dividing cells, such as disruption of the nuclear envelope, increased histone H3 phosphorylation, and enlargement of condensed chromatin regions. These changes were blocked when the expression of cyclin B, a key molecule for entry into the M phase in dividing cells, was deleted by in vivo genome editing. Furthermore, the activity-dependent expression of immediate early genes, such as c-fos and c-jun, was reduced in neurons even after two weeks from ten days of stimulation. These results indicate that neural hyperexcitation, especially when chronically repeated, leads to “M phase reentry” of neurons and chronic changes in gene expression and the three-dimensional nuclear structure. Our results provide insight into the molecular mechanisms underlying the chronic alternation of neurons induced by neural hyperexcitation and may contribute to developing new treatments for neuropsychiatric disorders that target nuclear changes in neurons. | | 2022年7月2日 15:30～15:45 沖縄コンベンションセンター 会議場B3・4 第6会場
3O06a2-03
活動依存的なゴルジ体局在変化による大脳皮質神経細胞の樹状突起精緻化
Activity-regulated positioning of the Golgi apparatus facilitates dendritic refinement in the developing mouse barrel cortex
*中川 直樹(1,2)、岩里 琢治(1,2)
1. 国立遺伝学研究所 神経回路構築研究室、2. 総合研究大学院大学 生命科学研究科 遺伝学専攻
*Naoki Nakagawa(1,2), Takuji Iwasato(1,2)
1. Laboratory of Mammalian Neural Circuits, National Institute of Genetics, Japan, 2. Department of Genetics, The Graduate University for Advanced Studies, SOKENDAI, Japan
Keyword: Golgi apparatus, activity-dependent development, dendritic refinement, barrel cortex
The neuronal activity-dependent refinement of dendrites is a developmental process essential for sculpting functional connectivity in the brain. However, it remains unclear how neuronal activity-evoked signals are transformed into the dendritic remodeling. Here, we show that the Golgi apparatus plays an instructive role in the activity-dependent dendritic refinement of neocortical neurons. In the neonatal mouse barrel cortex, driven by thalamic inputs, layer 4 excitatory neurons (barrel cells) refine their basal dendrites to acquire asymmetric geometries toward the barrel center, where the termini of corresponding thalamocortical axons form a cluster. We found that, corresponding to the time window of the dendritic refinement, the Golgi apparatus in barrel cells showed dramatic positional changes. The Golgi was localized predominantly in the apical dendrite at postnatal day 1 (P1), started to be observed in the soma at P3, and almost completely exited from the apical dendrite by P5. At P5, the Golgi showed strongly biased distribution in the soma toward the barrel center and was partially deployed into the longest, barrel center-oriented basal dendrite. These laterally polarized distributions of the Golgi apparatus mostly disappeared by P15 when the dendritic refinement was largely completed. Disruption of the polarized Golgi distribution by overexpressing a Golgi structural protein GRASP65 perturbed the barrel center-oriented dendritic patterning. This Golgi manipulation also impaired the firing specificity of barrel cells to the principal whisker stimulation. Genetic ablation of functional NMDA receptors (NMDARs), which mediate the dendritic refinement in barrel cells, attenuated the Golgi polarity. These findings reveal the developmental dynamics of the Golgi apparatus and their functions in the dendritic refinement. Regulated by NMDAR-mediated activity, the specific Golgi localization may contribute to selective extension and stabilization of dendrites that have wired with correct presynaptic targets. | | 2022年7月2日 15:45～16:00 沖縄コンベンションセンター 会議場B3・4 第6会場
3O06a2-04
Specific Lobular and Stripe Topography in the mouse Lateral Cerebellar nucleus
*Richard Nana Abankwah Owusu Mensah(1), Gideon Anokye Sarpong(3), Luo Yuanjun(1), Sugihara Izumi(1,2)
1. Graduate School of Medical and Dental Sciences, Tokyo Medical and Dental University, Tokyo, Japan, 2. Center for Brain Integration Research, Tokyo Medical and Dental University, Tokyo, Japan, 3. Neurobiology Research Unit, OIST Graduate University, Okinawa, Japan
Keyword: Lateral Cerebellar Nucleus, Purkinje cells, zebrin II, Stripe Topography
Objective: The lateral cerebellar nucleus (LN) receives innervation from hemispheric Purkinje cells and projects to brain regions responsible for various motor and cognitive functions, establishing its central role in the modulation of these activities by the cerebellum. Compared to the transversely-lobulated and longitudinally-striped compartmentalization of the cerebellar cortex, no equivalent spatial organization has been clarified in the LN. In this study, we tried to clarify the topographic spatial organization in the LN, by mapping termination areas of labeled Purkinje cell axons originating from different lobules and different stripes systematically in the mouse.
Methods: After craniotomy, dextran amine conjugated with Alexa Fluor 546, anterograde and retrograde tracers (about 10 nl) were injected into Purkinje cell layers of specific stripes in the hemisphere of anesthetized Aldoc-Venus mice. After a survival of 7 days, serial sections were cut from the dissected brain and images digitalized. We identified the injection site in lobules and longitudinal zebrin stripes, which are visualized in Aldoc-Venus mice. Purkinje cell axon termination areas were mapped in the cerebellar nuclei and then reconstructed in the three-dimensional model to compare their positions in the LN. In addition, we mapped retrogradely labeled neurons in the inferior olive to confirm the topographic relationship.
Results: So far, we mapped 62 cases of injections into the neighboring major hemispheric lobules; simple lobule, crus I, crus II, and paramedian lobule. Simple lobule, crus II and paramedian lobules projected to partly overlapping areas in the dorsal part of the LN. Crus I projected to the ventral part of the lateral nucleus. In both groups, the most lateral zebrin-positive (Z+) stripe (stripe 6+//7+) projected to the rostral part of the LN, while the next most lateral Z+ stripe (5+//6+) projected to the caudal part of the LN.
Discussion: The results indicated that the LN has a patterned lobular and stripe topographic arrangement. The results also indicated that crus I has a distinct neuronal connection pattern from the neighboring hemispheric lobules. This occurrence aligns with the idea that crus I is the particular hemispheric lobule more involved in cognitive function in the rodent cerebellum, presumably equivalent to crus I and crus II in the human and primate cerebellum. Consequently, the results suggest that the ventral part of the mouse LN may be more involved in cognitive function than the dorsal part. | |
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