幹細胞・細胞分化2 Stem cells and differentiation 2
O1-6-2-1 神経幹細胞におけるbHLH型転写因子の振動発現 Oscillatory Expression of bHLH Transcriptional Factors in Neural Stem Cells ○今吉格1, 影山龍一郎2 ○Itaru Imayoshi1, Ryoichiro Kageyama2 京都大学 白眉センター・ウイルス研究所1, 京都大学ウイルス研究所2 The Hakubi Center, Institute for Virus Research, Kyoto University1, Institute for Virus Research, Kyoto University2 During neural development and in the adult brain, neural stem cells give rise to appropriate numbers of neurons, astrocytes and oligodendrocytes in the specific timing and places. Many important intrinsic and extrinsic factors regulating the fate determination of neural stem cells have been identified, however, how do these key factors or molecules regulate diverse responses of neural stem cells is not still unclear. In this study, we performed real-time imaging of transcriptional activity and protein dynamics of bHLH factors (Hes1/5, Mash1, Olig2) in cultured neural stem cells. These bHLH factors were dynamically expressed in oscillatory manner by proliferating neural stem cells. Furthermore, FACS sorting and differentiation assay of neural stem cells having various amount of bHLH factors revealed that neural stem cells had the differentiation biases at that time, and that differentiation biases were dynamically changing by oscillatory expression of bHLH factors. These results indicate that neural stem cells are dynamically changing their state by oscillatory expression of fate determinate factors. We propose new neural stem cell regulatory mechanism that oscillatory expression of bHLH transcriptional factors ensures self-renewable and multi-potent ability of neural stem cells.	O1-6-2-2 ゼブラフィッシュ成魚脳内の新生ニューロン移動におけるSdf1/Cxcr4シグナリングの役割 Role of Sdf1/Cxcr4 signaling in the formation of the rostral migratory stream of new neurons along the blood vessels in the adult zebrafish brain ○岸本憲人1, 永井秀人1, 野平翔太1, 澤本和延1 ○Norihito Kishimoto1, Hideto Nagai1, Shota Nohira1, Kazunobu Sawamoto1 名古屋市立大学大学院 医学研究科 再生医学分野1 Department of Developmental and Regenerative Biology, Nagoya City University Graduate School of Medical Sciences1 In the adult mammalian brain, new neurons generated in the ventricular-subventricular zone (V-SVZ) migrate towards the olfactory bulb (OB) through the rostral migratory stream (RMS). We have previously reported that adult zebrafish also possesses a niche for neural stem cells (radial glial cells) at the V-SVZ, in which new neurons migrate into the OB forming a restricted path similar to the RMS along the blood vessels. Here, we studied the cellular and molecular mechanisms underlying the formation and maintenance of the RMS in the adult zebrafish. We found that radial glial cells in the V-SVZ extend their process to the blood vessels located along the outline of the RMS in the adult zebrafish brain. New neurons generated within the V-SVZ initially migrated short distance along radial glial fibers until reaching the blood vessels, before their rostral migration. Sdf1 immunoreactivity was observed along the radial glial fibers and the blood vessels. On the other hand, its receptor, Cxcr4, was detected in the new neurons. Perturbation of the Sdf1/Cxcr4 signaling resulted in a decrease in the number of new neurons that reached the blood vessels, eventually leading to a malformation of the RMS. These results suggest that the Sdf1/Cxcr4 chemokine signaling at the glio-vascular interface in the V-SVZ plays an important role in the formation and maintenance of the RMS in the adult zebrafish brain.
O1-6-2-3 生まれたてのニューロンのapical endfootによるNotchシグナルの調節を介した神経分化ペースのコントロール The apical endfoot of nascent neuron controls the pace of neurogenesis through the regulation of notch signaling ○畠山淳1, 若松義男2, 重本隆一3, 嶋村健児1 ○Jun Hatakeyama1, Yoshio Wakamatsu2, Ryuichi Shigemoto3, Kenji Shimamura1 熊本大学　発生医学研究所　脳発生分野1, 東北大学大学院医学研究科発生発達神経科学分野2, 生理学研究所脳形態解析3 Dept Brain Morpho, IMEG, Kumamoto Univ, Kumamoto1, Div Dev Neurosci, Graduate School of Medicine, Tohoku Univ, Sendai2, Div Cerecral Structure, NAIST, Okazaki3 Development of the vertebrate central nervous system (CNS) requires an exquisite balance between proliferation/self-renewal and differentiation of the neural progenitors. This balance is different spatially, between regions, as well as temporally, with each developmental stage. Notch signaling plays a pivotal role in regulating this balance, yet how signaling cells interact with receiving cells and how this balance is controlled spatially and temporally remain poorly understood. We have shown that the adherens junction facilitates efficient interaction of Notch1 and Dll1 to maintain the undifferentiated state of the neural stem cells in the developing neural tube. In fact, disruption of AJs that are formed between apical endfeet of progenitors and nascent neurons resulted in aberrant and precocious neurogenesis that was preceded by the down-regulation of Notch signaling. Conversely, prolonged retention of the apical endfeet of neurons by stabilizing AJs caused delay in neuron production. Concerning the molecular mechanism by which the neuronal apical endfeet regulate neurogenesis, we provide several lines of evidence that adherens junctions facilitate Notch signaling. Notch1 and Delta-like1 form complex with the constituents of adherens junctions, such as ZO1 and cadherin. Moreover live imaging of a fluorescent tagged-Notch1 protein revealed its translocation from the apical endfeet to the nuclei. Our results indicated that nascent neurons that express the ligands likely activate Notch signaling in neighboring progenitors at the apical endfeet to inhibit neural differentiation. We propose that the apical endfeet of neurons serve as a "pace-controller" for neurogenesis, thereby regulating histogenesis of the CNS tissues.	O1-6-2-4 Evi1 (Prdm3) maintains neuronal stem cell self-replication through epigenetic control over RBP-J recruitment ○Ka Yin Chung1, Tobias Hohenauer1, Adrian W. Moore1 Riken Brain Research Institute1 Development of cell diversity in the nervous system involves precisely regulated events coordinating the proliferation and differentiation of neural progenitor cells. Recently we described members of the evolutionarily conserved Prdm proto-oncogene transcription factor as new candidates to control neurogenesis. Evi1 (Prdm3) was originally identified as an oncogene causing myeloid leukemia in humans and mice. Here we show that Evi1 is expressed in several domains of neural precursors during embryonic neurogenesis, and we specifically investigate Evi1 function in the development of olfactory neurons. Evi1 is expressed in the Notch2/SOX2 positive apical precursor (AP) stem cell population; furthermore in Evi1-/- animals, similar to Notch mutants, AP cells exit the proliferative self replication cycle early leading to an increase in intermediate precursor cells positive for the proneural gene Neurogenin 1 (Ngn1). Among the best characterized Notch targets is Hes1. Hes1 is at the core of the regulatory network induced by Notch signaling to maintain stem cell self-replication. Evi1 binds at the Hes1 promoter in vivo. Evi1 alone does not induce Hes1 expression, but it amplifies the transcriptional induction of Hes1 by NICD. Examination of the histone methylation status across the Hes1 promoter suggests that Evi1 activity creates an 'activatable enhancer' signature at the Hes1 locus. These data suggest that Evi1/Notch co-regulated program enhances stem cell self-replication and cell cycle progression through Hes1.

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