演題:Imaging synaptic inhibition with Clomeleon, a genetically encoded
chloride indicator
日時:2006年2月23日
演者:George J. Augustine
(Department of Neurobiology, Duke University Medical Center, USA)
内容:Clomeleon
is a genetically encoded indicator that uses FRET to provide an absolute
measure of the internal Cl- concentration ([Cl-]i;).
We have developed transgenic mice with Clomeleon expression targeted
selectively to neurons by employing a neuron-specific promoter, Thy1. This
transgene was introduced into several lines of transgenic mice, each of which express
Clomeleon in specific subsets of neurons.
The ability of Clomeleon to
report changes in [Cl-]i associated withphasic
synaptic activity was tested in vitro by preparing acute slices from the brains
of these transgenic mice. [Cl-]i was imaged in brain
slices from the cerebellum, amygdala and hippocampus of 14−20-day-old mice. In all of these regions,
synaptic activation caused detectable rises in [Cl-]i,
although relatively large inhibitory events are required to produce an adequate
signal/noise. These results indicate that Clomeleon can report changes in [Cl-]i
associated with phasic synaptic inhibition, We also used Clomeleon to examine
the properties of tonic inhibition of cerebellar granule cells. Application of
the GABAA receptor antagonists reduced resting [Cl-]i in
these cells, due to blockade of tonic activation of GABAA receptors.
Cl- imaging allowed us to examine the spatial distribution of tonic inhibition
in the cerebellum. GABAA antagonists decreased [Cl-]i
in the molecular layer, where granule cell axons (parallel fibers) reside, and
also in some mossy fiber terminals. These results indicate that Clomeleon can
be used to image tonic release of GABA and that this release causes tonic
inhibition at several loci within the cerebellar cortex. In summary, Clomeleon
permits imaging of both phasic and tonic inhibition of central neurons in
vitro. This ability should enable imaging of the spatiotemporal dynamics of
inhibitory circuits in the brain.
主な論文
1.Duebel J, Haverkamp S, Schleich W, Feng G, Augustine GJ, Kuner T,
Euler T. (2006) Two-photon imaging reveals somatodendritic chloride gradient in
retinal ON-type bipolar cells expressing the biosensor Clomeleon. Neuron.
49:81-94.
2.Gitler, D., Y. Xu, H-T. Kao, D. Lin, S. Lim, J. Feng, P. Greengard,
and G.J. Augustine (2004) Molecular determinants of synapsin targeting to presynaptic
terminals. J. Neurosci. 24:3711-3720.
3.Nishiki T, Augustine GJ (2004) Synaptotagmin I synchronizes
transmitter release in mouse hippocampal neurons. J Neurosci 24:6127-6132.
4.Kuner, T. & G.J. Augustine (2000) A genetically ecoded
ratiometric indicator for chloride: capturing chloride transients in cultured hippocampal
neurons. Neuron 22: 447-459.
5.Miyata, M., E.A. Finch, L. Khiroug, K. Hashimoto, S. Hayasaka, S.-I.
Oda, M.Inouye, Y. Takagishi, G.J. Augustine & M. Kano (2000) Local calcium release
in dendritic spines required for long-term synaptic depression. Neuron 28: 233-244.
(担当:鍋倉淳一)