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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

GAD67 expression in the mouse vertical crista. (A) Schematic representation showing a representative slice (gray) of the crista ampullaris. Dots represent hair bundles protruding from the crista surface. E.C.: eminentia cruciata; P.S.: planum semilunatum. (B,C,D) Photomicrographs of a superficial confocal section of the slice schematized in (A) showing the cell nuclei (blue; DAPI), the cellular expression of GAD67 (green; GFP), and the merged image, respectively. Light blue indicates co-localization of nuclei and GFP, which seems poor because GAD67 is expressed in the cytoplasm. Most cell bodies at this confocal level appear sectioned transversally. (E) Photomicrograph of a lower confocal section of the same specimen (merged image). Most cell bodies appear now sectioned longitudinally, as inferred from their elongated shape.
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Figure 2: GAD67 expression in the mouse vertical crista. (A) Schematic representation showing a representative slice (gray) of the crista ampullaris. Dots represent hair bundles protruding from the crista surface. E.C.: eminentia cruciata; P.S.: planum semilunatum. (B,C,D) Photomicrographs of a superficial confocal section of the slice schematized in (A) showing the cell nuclei (blue; DAPI), the cellular expression of GAD67 (green; GFP), and the merged image, respectively. Light blue indicates co-localization of nuclei and GFP, which seems poor because GAD67 is expressed in the cytoplasm. Most cell bodies at this confocal level appear sectioned transversally. (E) Photomicrograph of a lower confocal section of the same specimen (merged image). Most cell bodies appear now sectioned longitudinally, as inferred from their elongated shape.

Mentions: Because of the complex morphology of the semicircular canal cristae, we created schematic representations to illustrate the plane of the slices. A representative image is shown in Figure 2A for a slice obtained by cutting the vertical ampulla parallel to the surface of the crista. The most central region consists of the eminentia cruciata (E.C.), which in the mouse is about 50 μm long (crista longitudinal axis) and 100 μm large (crista transverse axis), contains one or two layers of non-sensory cells and is devoid of hair cells and afferent and efferent innervation (Purcell and Perachio, 1997; Desai et al., 2005). The lateral areas of the crista are bounded by the planum semilunatum (P.S.), a non-sensory epithelium of semilunar shape with a high cellular density. Since the crista curves along the walls of the ampulla, confocal scanning from top to bottom will at first show the most lateral regions only, and then the rest of the crista. Moreover, since sensory and supporting cells in the crista are fan-like arranged, depending on the level of the confocal scanning they will appear sectioned mostly transversally (upper sections) or longitudinally (lower sections).


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)

GAD67 expression in the mouse vertical crista. (A) Schematic representation showing a representative slice (gray) of the crista ampullaris. Dots represent hair bundles protruding from the crista surface. E.C.: eminentia cruciata; P.S.: planum semilunatum. (B,C,D) Photomicrographs of a superficial confocal section of the slice schematized in (A) showing the cell nuclei (blue; DAPI), the cellular expression of GAD67 (green; GFP), and the merged image, respectively. Light blue indicates co-localization of nuclei and GFP, which seems poor because GAD67 is expressed in the cytoplasm. Most cell bodies at this confocal level appear sectioned transversally. (E) Photomicrograph of a lower confocal section of the same specimen (merged image). Most cell bodies appear now sectioned longitudinally, as inferred from their elongated shape.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: GAD67 expression in the mouse vertical crista. (A) Schematic representation showing a representative slice (gray) of the crista ampullaris. Dots represent hair bundles protruding from the crista surface. E.C.: eminentia cruciata; P.S.: planum semilunatum. (B,C,D) Photomicrographs of a superficial confocal section of the slice schematized in (A) showing the cell nuclei (blue; DAPI), the cellular expression of GAD67 (green; GFP), and the merged image, respectively. Light blue indicates co-localization of nuclei and GFP, which seems poor because GAD67 is expressed in the cytoplasm. Most cell bodies at this confocal level appear sectioned transversally. (E) Photomicrograph of a lower confocal section of the same specimen (merged image). Most cell bodies appear now sectioned longitudinally, as inferred from their elongated shape.
Mentions: Because of the complex morphology of the semicircular canal cristae, we created schematic representations to illustrate the plane of the slices. A representative image is shown in Figure 2A for a slice obtained by cutting the vertical ampulla parallel to the surface of the crista. The most central region consists of the eminentia cruciata (E.C.), which in the mouse is about 50 μm long (crista longitudinal axis) and 100 μm large (crista transverse axis), contains one or two layers of non-sensory cells and is devoid of hair cells and afferent and efferent innervation (Purcell and Perachio, 1997; Desai et al., 2005). The lateral areas of the crista are bounded by the planum semilunatum (P.S.), a non-sensory epithelium of semilunar shape with a high cellular density. Since the crista curves along the walls of the ampulla, confocal scanning from top to bottom will at first show the most lateral regions only, and then the rest of the crista. Moreover, since sensory and supporting cells in the crista are fan-like arranged, depending on the level of the confocal scanning they will appear sectioned mostly transversally (upper sections) or longitudinally (lower sections).

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