男女共同参画推進委員会シンポジウム 「次世代の担い手たちが創る神経科学の新しい潮流」
The Gender Equality Committee Program: Trends in Neuroscience created by young researchers
S3-5-1-1
ゼブラフィッシュ視覚神経回路の光遺伝学的解析
Optogenetic dissection of neural circuits underlying visually-guided reflexive behavior in larval zebrafish

○久保郁1
○Fumi Kubo1, Aristides Arrenberg2, Herwig Baier1
Max Planck Institute of Neurobiology, Germany1, University of Freiburg, Germany2

Vision plays essential roles in controlling animal behaviors enabling animals to produce an appropriate behavior in response to visual information they receive. To understand the neural mechanisms underlying visually-guided behaviors, we have applied optogenetic approaches in larval zebrafish by taking advantage of its optical transparency, genetic tractability and well-characterized behaviors. Retinal ganglion cell axons in larval zebrafish project to ten different visual areas in the brain, referred to as arborization fields (AF) 1-10, many of which have not been functionally characterized. Whole-field visual motion evokes robust eye movements, called the optokinetic response (OKR), involving the slow phase eye movements and saccades. It has been shown that the OKR does not require the optic tectum/AF-10, a major target of the retina, suggesting that this behavior is mediated by other retinal arborization field(s). Using transgenic zebrafish pan-neuronally expressing Halorhodopsin (NpHR) and locally illuminating a small area of the brain using a fine optic fiber, we found that optical silencing of a region that contains AF-9 suppressed the slow phase eye movements of the OKR. Optical stimulation of the AF-9 region using Channelrhodopsin-2 (ChR2) was sufficient to evoke the complete OKR consisting of both the slow phase and saccades, in the absence of visual stimuli. These results suggest that AF-9 is necessary and sufficient for the execution of the OKR.
S3-5-1-2
神経幹細胞分化における発生期酸素濃度の影響とその分子機構
Impact of oxygen levels on fate switching of neural stem cells during corticogenesis

○堅田明子1,2, 佐野坂司1,2, 武藤哲司1, 中島欽一1,2
○Sayako Katada1,2, Tsukasa Sanosaka1,2, Tetuji Mutoh1, Kinichi Nakashima1,2
奈良先端大院・バイオサイエンス・分子神経分化制御1, 九大院・医・応用幹細胞医科学2
Dept Biomedical Sciences, Nara Institute of Science and Technology, Nara1, School of Medicine, Kyusyu University2

Oxygen (O2) is a substrate for energy production and deeply involved in the regulations of cellular metabolism. Although standard cell culture systems are exposed to the environmental O2 level of 21% (normoxia), actual O2 concentration in both developing and adult brains is 1-8% (hypoxia). Accumulating studies have revealed that O2 and its signal transduction pathways control cell proliferation, differentiation, and morphogenesis during the development of various tissues. The mammalian brain cortex comprises deep- and upper-layer neurons (layer V-VI and II-IV, respectively) and glial cells including astrocytes. All these cells are sequentially generated from common multipotent neural stem cells (NSCs) in this order during development. Therefore, NSCs at midgestation produce neither upper-layer neuron nor astrocyte, but mainly differentiate into deep-layer neurons. In addition, it is generally known that this NSC's property change can be recapitulated in the embryonic stem (ES) cell culture systems. Recently, we have shown that the acquisition of astrogenic potential by NSCs is delayed in standard in vitro culture compared to those in vivo, while, in vitro culture under hypoxic condition can restore this impairment. Herein, we further analyze the impact of O2 levels during corticogenesis, i.e. deep- and upper-layer neuron production of NSCs. Mouse ES cells were cultured and induced to neural differentiation under normoxic or hypoxic condition, and the differentiation was evaluated by quantitative PCR and immunocytochemistry. We found that the expression of upper-layer specific neuronal genes in hypoxia culture appeared earlier than that in normoxia. Thus, it is conceivable that O2 levels contribute to appropriate scheduling of not only neuron-glia fate switching but also neuronal subtype specification throughout development.
S3-5-1-3
ショウジョウバエのステロイドホルモン生合成調節機構における生体アミン受容体の役割
The role of neurotransmitter receptors in the regulation of steroid hormone biosynthesis and developmental progression in Drosophila

○島田-丹羽裕子1, 梅井洋介1, マラムジナヤウゲニア1, 丹羽隆介1,2
○Yuko Shimada-Niwa1, Yosuke Umei1, Jevgenija Maramzina1, Ryusuke Niwa1,2
筑波大学 生命環境系1, JST、さきがけ2
Grad. School of Life and Environmental Sciences, Univ. of Tsukuba1, PRESTO, JST, Japan2

Steroid hormones play crucial role in many aspects of development, growth and reproduction. During insect development, the principal steroid hormone, ecdysone, is synthesized in a special endocrine organ called the prothoracic gland (PG). Ecdysone biosynthesis in PG is controlled in response to several external conditions, such as nutrition, temperature and photoperiod. This adaptive change of ecdysone biosynthesis results in flexible alterations of developmental timing such as molting. However, it remains unclear how external information is transmitted to PG to control ecdysone biosynthesis.
To uncover genes involved in controlling the adaptive regulation of ecdysone biosynthesis, we conducted a transgenic RNAi screen in Drosophila. Knocking down genes encoding certain neurotransmitter receptors in PG caused a decrease in ecdysone biosynthesis and developmental delay. This suggests that the timing of ecdysone biosynthesis in PG is controlled by neurotransmitters that are released from neurons. We identified a neuron that directly innervates PG. Genetic manipulations that inhibits its projection into PG resulted in a delay in pupariation. Dendrites of these neurons extend toward the subesophagal ganglion, known as the insect feeding center, implying that these neurons may receive signals related to food. Furthermore, the projection of the neurons to PG was affected by nutrient condition. We propose that environmental conditions are reflected on the developmental timing by a neuronal control, through neurotransmitters and their receptors.
S3-5-1-4
シナプス形成における補体ファミリー分子とグルタミン酸受容体のクロストーク
Cross talk between C1q family molecules and glutamate receptors in synapse formation

○松田恵子1, 柚崎通介1
○Keiko Matsuda1, Michisuke Yuzaki1
慶應義塾大学医学部1
Dept of Physiol, Sch of Med, Keio Univ1

For the appropriate synapse function, specialized pre- and postsynaptic regions must be precisely apposed to each other across a synaptic cleft. This step starts from recognition of target cells, leading to bidirectional differentiation. A growing number of molecules have been identified to function in synapse formation. In addition to receptor-type cell adhesion molecules, several secreted molecules have been shown to serve as synaptic organizers.C1q is the target recognition protein of the classical complement pathway in the immune response. Several C1q family members, especially the Cbln and C1q-like subfamilies, are highly and predominantly expressed in the central nervous system. We recently showed that Cbln1 is released from presynaptic neurons and regulates the integrity and functional plasticity of parallel fiber (PF)-Purkinje cell (PC) synapses in the cerebellum. Interestingly, mice lacking the glutamate receptor delta 2 (GluD2), a member of ionotropic glutamate receptor family, show strikingly similar phenotypes to mice lacking Cbln1. Indeed, GluD2 turned out to be the receptor for Cbln1 expressed in the postsynaptic PC dendrites. In addition, Cbln1 binds to the presynaptic receptor neurexin (Nrx), simultaneously. This tripartite Nrx-Cbln1-GluD2 synaptic organizer induces bidirectional synaptic differentiation and is absolutely required for the formation and maintenance of in PF-PC synapses in vivo. Cbln1 and other Cbln family members also exert unique functions in specific brain regions outside the cerebellum. Especially, Cbln1 and Cbln4 are expressed in the entorhinal cortex, which sends axons to the middle part of the molecular layer in the dentate gurus and CA1 stratum lacunosum moleculare in the hippocampus. We will discuss general roles of Cbln family proteins in the formation and maintenance of synapses in various brain regions.
S3-5-1-5
Spatiotemporal Gene Expression in Neurons
○Dan Ohtan Wang1
京都大学物質-細胞統合システム拠点(iCeMS)1
Institute for Integrated Cell-Material Sciences (iCeMS) Kyoto University1

mRNA localization and regulated translation can spatially restrict gene expression to each of the thousands of synaptic compartments formed by a single neuron, thereby vastly increasing the computational capacity of the brain. We have previously demonstrated that secondary structures of cis-elements in the UTRs can serve as synaptic localization signals thereby direct localization of mRNA to synapses. At synapses, learning-related stimuli activate local translation of specific transcripts, which contributes to persistent refinement of circuit connectivity. The remarkable specificity of local translation at synapses suggests robust molecular regulatory mechanisms. To study the dynamics of RNA regulation in neurons in order to understand spatiotemporal gene expression regulation mechanisms, we are currently developing imaging methods based on light-up probe technologies that allow us to monitor dynamic behaviors of mRNA in multiple living cellular contexts.


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