Lack of evidence for vesicular glutamate transporter expression in mouse astrocytes.

D. Li, K. Herault, K. Silm, A. Evrard, S. Wojcik, M. Oheim, E. Herzog, N. Ropert
Journal of Neuroscience. 2013-03-06; 33(10): 4434-4455
DOI: 10.1523/JNEUROSCI.3667-12.2013

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1. J Neurosci. 2013 Mar 6;33(10):4434-55. doi: 10.1523/JNEUROSCI.3667-12.2013.

Lack of evidence for vesicular glutamate transporter expression in mouse

Li D(1), Hérault K, Silm K, Evrard A, Wojcik S, Oheim M, Herzog E, Ropert N.

Author information:
(1)INSERM U603, CNRS UMR8154, Laboratoire de Neurophysiologie et Nouvelles
Microscopies, PRES Sorbonne Paris Cité, Université Paris Descartes, Paris,
F-75006 France.

The concept of a tripartite synapse including a presynaptic terminal, a
postsynaptic spine, and an astrocytic process that responds to neuronal activity
by fast gliotransmitter release, confers to the electrically silent astrocytes an
active role in information processing. However, the mechanisms of gliotransmitter
release are still highly controversial. The reported expression of all three
vesicular glutamate transporters (VGLUT1-3) by astrocytes suggests that
astrocytes, like neurons, may release glutamate by exocytosis. However, the
demonstration of astrocytic VGLUT expression is largely based on immunostaining,
and the possibility of nonspecific labeling needs to be systematically addressed.
We therefore examined the expression of VGLUT1-3 in astrocytes, both in culture
and in situ. We used Western blots and single-vesicle imaging by total internal
reflection fluorescence microscopy in live cultured astrocytes, and confocal
microscopy, at the cellular level in cortical, hippocampal, and cerebellar brain
slices, combined with quantitative image analysis. Control experiments were
systematically performed in cultured astrocytes using wild-type, VGLUT1-3
knock-out, VGLUT1(Venus) knock-in, and VGLUT2-EGFP transgenic mice. In fixed
brain slices, we quantified the degree of overlap between VGLUT1-3 and neuronal
or astrocytic markers, both in an object-based manner using fluorescence line
profiles, and in a pixel-based manner using dual-color scatter plots followed by
the calculation of Pearson’s correlation coefficient over all pixels with
intensities significantly different from background. Our data provide no evidence
in favor of the expression of any of the three VGLUTs by gray matter protoplasmic
astrocytes of the primary somatosensory cortex, the thalamic ventrobasal nucleus,
the hippocampus, and the cerebellum.

DOI: 10.1523/JNEUROSCI.3667-12.2013
PMID: 23467360 [Indexed for MEDLINE]

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