1996 Fiscal Year Final Research Report Summary
Nerve-muscle interaction during synapse formation and the role of genes
| Project/Area Number |
06404086
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| Research Category |
Grant-in-Aid for Scientific Research (A)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
神経・脳内生理学
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| Research Institution | GUNMA UNIVERSITY SCHOOL OF MEDICINE |
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Principal Investigator |
KIDOKORO Yoshiaki Gunma University School of Medicine, Professor, 医学部, 教授 (00053083)
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| Co-Investigator(Kenkyū-buntansha) |
YOSHIHARA Motojiro , 助手 (80222397)
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| Project Period (FY) |
1994 – 1996
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| Keywords | synapse formation / genes / Drosophila / glutamate receptor / receptor accumulation / ion permeation / channel kinetics / シナプス外型チャネル |
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| Research Abstract |
Synaptic transmission is the basis of all human behaviors ranging from "simple" motor reflexes to "higher cognitive functions. While considerable progress has been make to resolve the broad outlines of synaptic development and transmission, the molecular events are still vague. To address this problem we must have a model system in which we can use as many modern analytical tools as possible. The model system that we have chosen is the fruit fly, Drosophila melanogaster. The ultimate goal of this proposal to elucidate the gene control mechanism of synapse formation. During the tenure of the three year grant, we have accomplished the followings ; 1) Ion permeation mechanism of glutamate receptor channels. In collaboration with Professor Sergio Ciani at UCLA we have examined the ion permeation mechanism of Drosophila glutamate receptor channels and developed a model based on Eyring's rate reaction theory. I-V curves under a variety of ionic environment were well fitted with this model. F
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urthermore, this model was successfully extended to the mammalian NMDA receptor channel. 2) Kinetics of the Drosophila glutamate receptor channel. Insect glutamate receptor channel has a large unitary conductance and is suitable kinetic studies. We have examined the kinetics in detail. Two agonist molecules are required to open the channel to the main open state while one molecule opens it briefly. These properties are similar to that of the ACh receptor channel. The dissociation constants are in the mM range. 3) Synapse formation. Synaptic transmission was studied in embryos using patch-clamp techniques. 16 hours after fertilization spontaneous synaptic currents, miniature synaptic currents, start to appear. The amplitude increased gradually toward 21 hours after fertilization, which is the time of hatching. During this period receptors accumulate at the subsynaptic membrane. To visualize the receptor distribution we raised antibodies against a receptor subunit. Small receptor clusters were found even before nerve-muscle contact. These receptor clusters dissipate before accumulation of receptors at the synapse. 4) A novel mutant which has defects in synaptic transmission. We generated over 1000 mutants using P element mutagenesis and screened them. One mutant was found which has defects in pre- and postsynaptic elements. The gene was located at 5 9D-E on the second chromosome. In collaboration with Professor Yoshiki Hotta's group at University of Tokyo we cloned the gene and currently are trying to raise antibodies against the gene product. Although we are far from the final goal we have laid a solid ground for further development. Less
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