Oral
Non’ vertebrate models and synapses
一般口演
無脊椎生物とシナプス |
|---|
| 7月28日（日）10:50～11:05 第10会場（万代島ビル 6F 会議室）
4O-10a1-1
ショウジョウバエにおいて甘味味覚感覚ニューロンの下流側にシナプス接続する相手の包括的なカタログ
Takaaki Miyazaki（宮崎 隆明）1,2,3，Tzu-Yang Lin（林 子暘）1，Chi-hon Lee（李 奇鴻）1，Mark Stopfer（ストッファー，マーク）1，Kei Ito（伊藤 啓）2，Emiko Suzuki（鈴木 えみ子）3,4
1NIH-NICHD, Bethesda, Maryland, USA
2東京大・分生研
3国立遺伝研
4総研大院
Sugar stimuli detected by the gustatory system serve as cues for choice of more favorable food source as well as triggers for immediate feeding behaviors. They also act as reward cues for associative learning. With a relatively simple nervous system and a plethora of genetic tools, Drosophila affords an excellent model for mapping neural circuits and testing their functions. In this model organism, a specific subpopulation of gustatory sensory neurons (GSNs) in the mouth relay sugar information to a distinct subregion in the brain, suggesting that different types of postsynaptic neurons are involved in shaping distinct sugar-related behaviors. However, it is still unknown how many types of gustatory second-order neurons (G2Ns) receive synaptic inputs from sugar-responsive GSNs. To identify subpopulation of the G2Ns, we conducted an anatomical screen of more than 5,000 GAL4 strains, each of which genetically labels a specific subpopulation of neurons. We identified 16 strains labeling 15 types of G2Ns (G2N-1 - 15). Each type exhibited unique morphology of neural fibers, showing that they are non-overlapping populations of neurons. The number of neurons of each G2N type ranged from 2 to about 40. Intriguingly, for 5 types, each of them consists of only a single neuron per hemisphere, implying unexpected diversity of the G2Ns. When we visualized a whole population of postsynaptic partners of sugar-sensitive GSNs using the trans-Tango technique, about 150 neurons were labeled. This number corresponded to the sum of the G2Ns labeled in the GAL4 lines, suggesting that our results cover almost all G2Ns connected to sugar-sensitive GSNs.
Further, we investigated whether the identified G2Ns connect to neural circuits involved in taste-related behaviors. Among the 15candidate G2Ns, seven types send neural fibers to the dendritic region of feeding command neurons, which trigger a series of feeding behaviors upon appetitive stimulation. Four types of G2Ns project to the input regions of octopaminergic neurons, which reportedly convey reward signals necessary for associative olfactory learning. These observations suggest that the G2Ns may convey information for direct feeding behavior or associative memory. Our results provide ways to genetically manipulate G2Ns for live-imaging of single-neuron activities and behavioral assays, which should reveal the information processing pathways required for appropriate control of the multiple sugar-related behaviors. | | 7月28日（日）11:05～11:20 第10会場（万代島ビル 6F 会議室）
4O-10a1-2
ショウジョウバエHDACによる非ヒストンタンパクの脱アセチル化を介した遺伝子発現誘導の時間制御
Yukinori Hirano（平野 恭敬），Mai Takakura（高倉 麻衣）
京都大白眉
Transient gene expression induced by neural activation is an essential process in memory consolidation. However, the molecular mechanisms by which the transient time window for gene expression is determined, and its physiological role in memory are still unknown. The epigenetic regulation, such as histone acetylation mediated by histone acetyltransferases (HATs) and histone deacetylases (HDACs), is involved in gene expression. Those regulation could contribute to opening and closing the time window allowing gene expression required for memory consolidation. Here we report that deacetylation by HDAC determines the time window for gene expression in Drosophila, but the deacetylation target is non-histone protein, the transcriptional corepressor, CoRest. The LC-MS/MS analysis of HDAC proteins purified from the memory center, mushroom body in flies indicated that the neural activation induces changes in their interaction with CoRest, in the isoform-specific manner. We found that this interaction change is mediated by acetylation of the specific isoform of CoRest proteins. After the complex formation was switched through the acetylation, the acetylated CoRest was reversed by HDAC, and the HDAC/CoRest complex returned to the basal complex, suggesting that acetylation of the specific isoform of CoRest may be involved in gene expression. Accordingly, impairment of acetylation of CoRest proteins inhibited gene expression and memory consolidation in olfactory aversive training paradigm. In contrast, acceleration of the interaction change of the HDAC/CoRest complex elongated the time window for gene expression, and also facilitated memory consolidation. Thus, acetylation and deacetylation of non-histone protein, CoRest, regulates the function of HDAC, which transiently controls gene expression to occur in memory consolidation. | | 7月28日（日）11:20～11:35 第10会場（万代島ビル 6F 会議室）
4O-10a1-3
行動可塑性に関わる感覚神経のシナプス放出変化とDAG経路による制御の解明
Hinako Mitsui（三井 日菜子），Hirofumi Sato（佐藤 博文），Hirofumi Kunitomo（國友 博文），Yuichi Iino（飯野 雄一）
東京大院理生物科学
Animals have the ability to alter their behavior based on past experiences. Despite its importance, the mechanisms of this behavioral modification remain poorly understood.
C. elegans is an ideal organism for studying the mechanisms of learning. C. elegans memorizes NaCl concentration during cultivation and shows strong preference for learned NaCl concentrations. Our lab recently found the response of the interneuron AIB to signaling from the upstream sensory neuron ASER can be inverted based on NaCl concentration during cultivation. While ASER activates in response to NaCl concentration decrease regardless of cultivation concentration, AIB activates in response to NaCl decrease only when animals were cultivated at higher NaCl concentrations than test conditions. Despite these observations, the molecular mechanisms of ASER-AIB synaptic plasticity are not fully understood. Previous research has reported that the DAG pathway is critical in determining salt preference: when the DAG pathway is activated in ASER, animals are attracted to high NaCl concentration. When the DAG pathway is deactivated, animals move towards lower NaCl concentrations (Kunitomo et al. 2013). Because the DAG pathway is involved in the release of neuropeptides and glutamate (Sieburth et al. 2007, Ventimiglia et al. 2017), we focused on the release of neurotransmitters from ASER and tried to clarify whether there is any difference in release of neurotransmitters between wild type and DAG mutants. We also investigated the effects of conditioning on neurotransmitter release.
To observe glutamate release, we expressed VGLUT::pHluorin in ASER. In wild type animals, the rate of glutamate release changed depending on conditioning: the ratio of glutamate release increased substantially after cultivation with high salt, while cultivation with low salt showed a modest release. We also observed glutamate release in two DAG mutants; pkc-1(lf) in which the DAG pathway shows reduced activity, and egl-30(gf) in which the DAG pathway is strongly activated.
We found that the DAG pathway positively regulates glutamate release from ASER; the increased glutamate release is associated with the animal's preference for high NaCl concentrations, and decreased release is associated with preference for low NaCl concentrations. These results suggest the regulation of glutamate release by the DAG pathway is the basis for experience-dependent salt chemotaxis in C. elegans. | | 7月28日（日）11:35～11:50 第10会場（万代島ビル 6F 会議室）
4O-10a1-4
モデル生物を用いた血液脳関門の普遍原理の解析
Hiroshi Kanda（菅田 浩司），Rieko Shimamura（島村 理恵子），Michiko Koizumi-Kitajima（小泉-北島 美智子），Hideyuki Okano（岡野 栄之）
慶應大医生理
The blood-brain barrier, or BBB, is a tissue architecture that regulates the strongly 'isolated' microenvironment of the brain. In the mammalian central nervous system (CNS), the BBB is established by microvascular capillary endothelial cells. The paracellular permeability of the most hydrophilic molecules from the circulation into the brain is restricted by tight junctions (TJs) between endothelial cells. A growing body of research has identified junctional proteins, as well as intracellular molecules, that regulate the properties of the BBB. However, how these molecules are regulated remains unresolved.
Drosophila melanogaster, or fruit fly, is an excellent model organism to study the evolutionarily-conserved mechanism, which is required for the integrity of BBB. We have performed an in vivo RNAi screen to identify genes that are essential for the integrity of BBB. Here, we report that one of two Drosophila matrix metalloproteinases, Mmp2, is essential for the establishment of the BBB in Drosophila. In the central nervous system, Mmp2 is highly expressed in the BBB-forming cells. We find that the regulation of the amounts of certain ECM components, such as type IV collagen, is critical for the establishment of the BBB. We also show that the process of mesenchymal-epithelial transition of the BBB-forming cells is perturbed in the absence of Mmp2. These data strongly indicate that Mmps, which is typically thought to be one of the major risk factors for BBB degradation, is essential for BBB integrity in Drosophila. Thus, our results, together with the comparative simplicity of the two-member family of Mmp proteins in Drosophila, may provide impetus for more comprehensive studies of previously undiscovered aspects of this protein family in the context of BBB regulation. | |
|
|
