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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 longitudinal slices of the mouse vertical crista. (A) Schematic representation showing the plane of the slice. Note that the section is not through the center of the crista (i.e., it is not a medial section). (B) Merged photomicrograph showing the expression of GAD67. Note the absence of GAD67 expression in the E.C. (white arrow). (C) Enlargement of a portion of the same image as in (B), showing in better detail the shape and position of the cells expressing GAD67. The white arrow points at the nuclear region of a supporting cell. The red arrow points at a nucleus of a hair cell.
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Figure 4: GAD67 expression in longitudinal slices of the mouse vertical crista. (A) Schematic representation showing the plane of the slice. Note that the section is not through the center of the crista (i.e., it is not a medial section). (B) Merged photomicrograph showing the expression of GAD67. Note the absence of GAD67 expression in the E.C. (white arrow). (C) Enlargement of a portion of the same image as in (B), showing in better detail the shape and position of the cells expressing GAD67. The white arrow points at the nuclear region of a supporting cell. The red arrow points at a nucleus of a hair cell.

Mentions: Figure 2B shows a representative photomicrograph of an upper section of the slice cut as shown in Figure 2A. Here and in the next images cell nuclei are labeled with DAPI (blue). Note that GAD67 (Figure 2C, green) is expressed in the peripheral zone (P.Z.) of the crista, whereas no staining is present in the central zone (C.Z.) nor in the E.C. Merge of Figures 2B,C is shown in Figure 2D. Most cells at this section level are cut transversally. Figure 2E shows a photomicrograph of a lower section of the same specimen. Note that, despite the impression that stained cells are now dispersed throughout the crista, because of the complex crista morphology as discussed above, they are actually located in the P.Z. only. To confirm this, we also performed transverse and longitudinal slices. Figure 3 shows two representative transverse sections from a same vertical crista. Consistent with the previous images, GAD67 expression was not detectable in the C.Z. (Figure 3C) and in the E.C. (Figure 3D). At this magnification the shape and location of the GAD67-positive cells is also clear and typical of supporting cells—see also Figure 4C below. Note in fact their small nuclear regions (red arrowheads), which are aligned and in contact with the basement membrane, and their thin, thread-like bodies running in-between the sensory cells prior to enlarge at the apical (luminal) surface. In contrast, the nuclei of sensory hair cells (yellow arrowheads) occupy the upper layer and are slightly staggered to form a pseudostratified epithelium.


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 longitudinal slices of the mouse vertical crista. (A) Schematic representation showing the plane of the slice. Note that the section is not through the center of the crista (i.e., it is not a medial section). (B) Merged photomicrograph showing the expression of GAD67. Note the absence of GAD67 expression in the E.C. (white arrow). (C) Enlargement of a portion of the same image as in (B), showing in better detail the shape and position of the cells expressing GAD67. The white arrow points at the nuclear region of a supporting cell. The red arrow points at a nucleus of a hair cell.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 4: GAD67 expression in longitudinal slices of the mouse vertical crista. (A) Schematic representation showing the plane of the slice. Note that the section is not through the center of the crista (i.e., it is not a medial section). (B) Merged photomicrograph showing the expression of GAD67. Note the absence of GAD67 expression in the E.C. (white arrow). (C) Enlargement of a portion of the same image as in (B), showing in better detail the shape and position of the cells expressing GAD67. The white arrow points at the nuclear region of a supporting cell. The red arrow points at a nucleus of a hair cell.
Mentions: Figure 2B shows a representative photomicrograph of an upper section of the slice cut as shown in Figure 2A. Here and in the next images cell nuclei are labeled with DAPI (blue). Note that GAD67 (Figure 2C, green) is expressed in the peripheral zone (P.Z.) of the crista, whereas no staining is present in the central zone (C.Z.) nor in the E.C. Merge of Figures 2B,C is shown in Figure 2D. Most cells at this section level are cut transversally. Figure 2E shows a photomicrograph of a lower section of the same specimen. Note that, despite the impression that stained cells are now dispersed throughout the crista, because of the complex crista morphology as discussed above, they are actually located in the P.Z. only. To confirm this, we also performed transverse and longitudinal slices. Figure 3 shows two representative transverse sections from a same vertical crista. Consistent with the previous images, GAD67 expression was not detectable in the C.Z. (Figure 3C) and in the E.C. (Figure 3D). At this magnification the shape and location of the GAD67-positive cells is also clear and typical of supporting cells—see also Figure 4C below. Note in fact their small nuclear regions (red arrowheads), which are aligned and in contact with the basement membrane, and their thin, thread-like bodies running in-between the sensory cells prior to enlarge at the apical (luminal) surface. In contrast, the nuclei of sensory hair cells (yellow arrowheads) occupy the upper layer and are slightly staggered to form a pseudostratified epithelium.

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