シンポジウム32
精神神経疾患研究への展開を見据えた時空間的な遺伝子発現制御研究の最先端 |
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| S32-1
神経分化過程におけるDNAメチル化のダイナミクスとその役割
味岡 逸樹
東京医科歯科大・脳統合機能研究センター
During neuronal differentiation, gene expression must be spatio-temporally coordinated to undergo each step of differentiation such as migration, neurite extension, and synaptogenesis. DNA methylation is one of the best studied epigenetic modifications important for the spatio-temporal control of gene expression. However, the roles and the dynamics of DNA methylation during neuronal differentiation are mostly unknown.
I have been interested in understanding how neurons lose proliferation potency during development and have been focusing on the tumor suppressor gene Rb and its family members（p107 and p130）to understand it. We recently found that differentiating cerebral cortical excitatory neurons underwent S-phase progression but not cell division after acute Rb family inactivation in differentiating neurons（Oshikawa et al., Development, 2013）. However, the differentiating neurons underwent cell division and proliferated when Rb family members were inactivated in cortical progenitors. Differentiating neurons generated from Rb family-deficient progenitors, but not acutely inactivated Rb family in differentiating neurons, activated the DNA double-strand break（DSB）repair pathway. The activation of the DSB repair pathway was essential for the cell division of Rb family-deficient differentiating neurons. Interestingly, DNA methylation during neurogenesis is important for the protection from the DSB repair pathway activation and the cell division of Rb family-deficient differentiating neurons.
In this symposium, I will share our recent data addressing the dynamics of DNA methylation during neuronal differentiation and will discuss its roles. |
| S32-2
神経細胞における転写因子動態の1分子イメージング
菅生 紀之
大阪大学大学院生命機能研究科細胞分子神経生物学研究室
Neuronal activity influences circuit formation and synaptic plasticity. How such neuronal activity regulates gene expression is one of the key issues in the development and function of the nervous system. Proper spatiotemporal gene expression is achieved by dynamic interactions between transcription factors and their target sites in the genome. However, the kinetics of transcription factor binding to DNA in response to neuronal activity is totally unknown. Here we investigated basal and activity-dependent DNA binding and dissociation events of cAMP-response element binding protein（CREB）, a principal transcription factor in activity-dependent transcription, single-molecule imaging. The fluorescent-tagged CREB in vitro and in living cortical neurons was observed by total internal reflection fluorescence microscopy and highly inclined laminated optical sheet microscopy, respectively. The fluorescent-tagged CREB bound specifically to its target DNA sequence cAMP-response element for a remarkably longer period（dissociation rate constant：0.21 s-1）than to an unrelated sequence（2.74 s-1）. Moreover, we found that CREB also resided at restricted positions in the nuclei of living cortical neurons for a comparable period, but the residence time distribution was not affected by alteration of neuronal activity or its association with the CREB cofactor cAMP-regulated transcriptional co-activator 1. These results suggest that basal binding of CREB with its cofactor to CRE in the time range of several seconds is prerequisite for activity-dependent transcription. The present imaging approach enables us to monitor the dynamics of various transcription factors on DNA in neurons. |
| S32-3
神経可塑性におけるmRNAのシナプス局在及び発現制御
Dan Ohtan Wang
京都大学細胞―物質統合システム拠点
A neuron is highly polarized, asymmetric, and has thousands of functional subcellular compartments such as synapse. Such complex geometry requires effective mRNA trafficking and regulated local translation pathways to spatially restrict gene expression inside a functional neuron. We and others have previously demonstrated that learning-related stimuli at synapses can trigger local protein synthesis in a synapse-, stimulus-, and transcript-specific manner（Wang et al., Science, 2009；Wang et al., TINS, 2010）. However, the molecular and cellular mechanisms that endow neurons with such remarkable specific regulation are unknown. What are the properties of motile units responsible for mRNA trafficking? What mechanisms repress translation during mRNA transport? How do local activities turn on translation of specific transcripts? How is mRNA degradation regulated within neuronal compartments? I will talk about our approach to answer these questions and touch upon recent advancements in RNA live-cell imaging. |
| S32-4
統合失調症関連遺伝子とクロマチン制御
山本 直樹，西川 徹
東京医科歯科大院・医歯・精神行動医科学
Symptoms of schizophrenia usually appear just after adolescent period, suggesting presumable changes of some neural network（s）during the critical period. To get more inclusive insights into the molecular basis of schizophrenia, we have investigated the gene expression profiles after acute methamphetamine（MAP, an indirect dopamine agonist）and phencyclidine（PCP, an NMDA type glutamate receptor antagonist）injection at postnatal days 8, 18, 25 and 50 in the rat neocortex by using a microarray technology. Our results suggest these responsive genes may be involved in the ontogenic development-dependent molecular cascades that underlie the MAP- and PCP-induction of abnormal behavior and psychosis, and some of the schizophrenic symptoms, as as the novel candidates for the schizophrenia-related molecules. According to our developmental pharmacological hypothesis of schizophrenia, the critical period-related MAP- and PCP-responsive transcripts could compose the molecular cascades that might be involved in the pathophysiology of schizophrenia. Therefore, we further investigated association between these responsive genes and schizophrenia. The single nucleotide polymorphisms（SNPs）of promoter/enhancer, insulator, and splicing enhancer/silencer regions of some of these candidate genes were found to be associated with schizophrenia. Furthermore, a histone 2A variant protein, which is negatively regulated by microRNA, also showed significant genetic association with schizophrenia. These observations suggest the regulation of critical gene expression through chromatin remodeling in the brain regions might be involved in the schizophrenic symptoms in a development-dependent manner. | |
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