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Glutamic acid decarboxylase 67 expression by a distinct population of mouse vestibular supporting cells.

Tavazzani E, Tritto S, Spaiardi P, Botta L, Manca M, Prigioni I, Masetto S, Russo G - Front Cell Neurosci (2014)

Bottom Line: While no evidence for GAD65 expression was found, GAD67 was detected in a distinct population of peripherally-located supporting cells, but not in hair cells or in centrally-located supporting cells.GABA, on the other hand, was found in all supporting cells.The present result indicate that only a discrete population of supporting cells use GAD67 to synthesize GABA.

View Article: PubMed Central - PubMed

Affiliation: Department of Brain and Behavioral Sciences, University of Pavia Pavia, Italy.

ABSTRACT
The function of the enzyme glutamate decarboxylase (GAD) is to convert glutamate in γ-aminobutyric acid (GABA). Glutamate decarboxylase exists as two major isoforms, termed GAD65 and GAD67, that are usually expressed in GABA-containing neurons in the central nervous system. GAD65 has been proposed to be associated with GABA exocytosis whereas GAD67 with GABA metabolism. In the present immunofluorescence study, we have investigated the presence of the two GAD isoforms in the semicircular canal cristae of wild type and GAD67-GFP knock-in mice. While no evidence for GAD65 expression was found, GAD67 was detected in a distinct population of peripherally-located supporting cells, but not in hair cells or in centrally-located supporting cells. GABA, on the other hand, was found in all supporting cells. The present result indicate that only a discrete population of supporting cells use GAD67 to synthesize GABA. This is the first report of a marker that allows to distinguish two populations of supporting cells in the vestibular epithelium. On the other hand, the lack of GABA and GAD enzymes in hair cells excludes its involvement in afferent transmission.

No MeSH data available.


Related in: MedlinePlus

GABA expression in the mouse cristae. (A) Photomicrograph of a confocal section from a longitudinal slice of a vertical crista. As shown in the schematic representation on the left, the picture refers to the peripheral zone. Note the co-localization (yellow arrowheads) of GABA (red) and GAD67 (green) in many supporting cells. (B) Higher magnification from a different vertical crista section showing GABA and GAD67 co-localization (yellow arrowheads) or GABA-only expression (white arrowhead) in three different supporting cells. (C) Confocal images from two longitudinal slices of a horizontal crista depicting the peripheral (a) and the central (b) zone. Most peripheral supporting cells co-express GABA and GAD67, while central supporting cells only express GABA. No GABA expression was ever found in hair cells.
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Figure 8: GABA expression in the mouse cristae. (A) Photomicrograph of a confocal section from a longitudinal slice of a vertical crista. As shown in the schematic representation on the left, the picture refers to the peripheral zone. Note the co-localization (yellow arrowheads) of GABA (red) and GAD67 (green) in many supporting cells. (B) Higher magnification from a different vertical crista section showing GABA and GAD67 co-localization (yellow arrowheads) or GABA-only expression (white arrowhead) in three different supporting cells. (C) Confocal images from two longitudinal slices of a horizontal crista depicting the peripheral (a) and the central (b) zone. Most peripheral supporting cells co-express GABA and GAD67, while central supporting cells only express GABA. No GABA expression was ever found in hair cells.

Mentions: Finally, in order to test for the possible co-localization of GAD67 and GABA in the sensory crista epithelium, we performed a set of experiments in which GABA immunofluorescence was also tested in transgenic GAD67-GFP mice. As shown in Figure 8, GABA positivity was detected in all supporting cells, either expressing or not GAD67. No GABA expression was found in any hair cell.


Glutamic acid decarboxylase 67 expression by a distinct population of mouse vestibular supporting cells.

Tavazzani E, Tritto S, Spaiardi P, Botta L, Manca M, Prigioni I, Masetto S, Russo G - Front Cell Neurosci (2014)

GABA expression in the mouse cristae. (A) Photomicrograph of a confocal section from a longitudinal slice of a vertical crista. As shown in the schematic representation on the left, the picture refers to the peripheral zone. Note the co-localization (yellow arrowheads) of GABA (red) and GAD67 (green) in many supporting cells. (B) Higher magnification from a different vertical crista section showing GABA and GAD67 co-localization (yellow arrowheads) or GABA-only expression (white arrowhead) in three different supporting cells. (C) Confocal images from two longitudinal slices of a horizontal crista depicting the peripheral (a) and the central (b) zone. Most peripheral supporting cells co-express GABA and GAD67, while central supporting cells only express GABA. No GABA expression was ever found in hair cells.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4269132&req=5

Figure 8: GABA expression in the mouse cristae. (A) Photomicrograph of a confocal section from a longitudinal slice of a vertical crista. As shown in the schematic representation on the left, the picture refers to the peripheral zone. Note the co-localization (yellow arrowheads) of GABA (red) and GAD67 (green) in many supporting cells. (B) Higher magnification from a different vertical crista section showing GABA and GAD67 co-localization (yellow arrowheads) or GABA-only expression (white arrowhead) in three different supporting cells. (C) Confocal images from two longitudinal slices of a horizontal crista depicting the peripheral (a) and the central (b) zone. Most peripheral supporting cells co-express GABA and GAD67, while central supporting cells only express GABA. No GABA expression was ever found in hair cells.
Mentions: Finally, in order to test for the possible co-localization of GAD67 and GABA in the sensory crista epithelium, we performed a set of experiments in which GABA immunofluorescence was also tested in transgenic GAD67-GFP mice. As shown in Figure 8, GABA positivity was detected in all supporting cells, either expressing or not GAD67. No GABA expression was found in any hair cell.

Bottom Line: While no evidence for GAD65 expression was found, GAD67 was detected in a distinct population of peripherally-located supporting cells, but not in hair cells or in centrally-located supporting cells.GABA, on the other hand, was found in all supporting cells.The present result indicate that only a discrete population of supporting cells use GAD67 to synthesize GABA.

View Article: PubMed Central - PubMed

Affiliation: Department of Brain and Behavioral Sciences, University of Pavia Pavia, Italy.

ABSTRACT
The function of the enzyme glutamate decarboxylase (GAD) is to convert glutamate in γ-aminobutyric acid (GABA). Glutamate decarboxylase exists as two major isoforms, termed GAD65 and GAD67, that are usually expressed in GABA-containing neurons in the central nervous system. GAD65 has been proposed to be associated with GABA exocytosis whereas GAD67 with GABA metabolism. In the present immunofluorescence study, we have investigated the presence of the two GAD isoforms in the semicircular canal cristae of wild type and GAD67-GFP knock-in mice. While no evidence for GAD65 expression was found, GAD67 was detected in a distinct population of peripherally-located supporting cells, but not in hair cells or in centrally-located supporting cells. GABA, on the other hand, was found in all supporting cells. The present result indicate that only a discrete population of supporting cells use GAD67 to synthesize GABA. This is the first report of a marker that allows to distinguish two populations of supporting cells in the vestibular epithelium. On the other hand, the lack of GABA and GAD enzymes in hair cells excludes its involvement in afferent transmission.

No MeSH data available.


Related in: MedlinePlus