The Timing of  -Gustducin Expression during Cell Renewal in Rat Vallate Taste Buds

Abstract

The G protein subunit alpha-gustducin is expressed in a subset of light (Type II) but not in dark (Type I) cells in rat vallate taste buds. The thymidine analogue 5-bromo-2'-deoxyuridine (BrdU) is incorporated into DNA during the S-phase of the cell cycle and can be used to determine the time of origin of a cell. In this study, 31 rats were injected with BrdU (50 mg/kg i.p.) and perfused at various times, from 2.5 to 10.5 days, following BrdU administration. Vallate papillae were embedded in polyester wax, cut into 4 microm transverse sections, and characterized with antibodies to BrdU and alpha-gustducin. Sections were processed for indirect immunofluorescence or with an immunoperoxidase procedure. From immunoperoxidase material on 21 rats, counts of alpha-gustducin- and BrdU-labeled cells were obtained from 300-800 taste bud profiles at each survival time; a total of 4122 taste bud profiles were examined. Cells with nuclei immunoreactive for BrdU occurred within the taste buds at 2.5 days and double-labeled cells were clearly evident at 3.5 days; a small number of double-labeled cells were seen as early as 2.5 days. Double-labeled cells reached a peak at 6.5 days and did not decline significantly by 10.5 days. Cells labeled for BrdU but not alpha-gustducin peaked at 5.5 days and showed a significant decline by 8.5 days. These latter cells included light cells not expressing alpha-gustducin and dark cells, which have previously been shown to have a shorter life span than light cells. These data suggest that expression of alpha-gustducin appears very early in a cell's life span and that these cells are longer lived than many of the cells that do not express this G protein.

Differential expression of a BMP4 reporter allele in anterior fungiform versus posterior circumvallate taste buds of mice

“…This timeframe is consistent with reports where taste cells typically express markers of differentiation by 2.5-3.5 days after birth. For example, expression of BrdU in gustducin-IR cells is first detected 2.5 days after injection [30,31]. …”

“…Birthdating studies, however, imply that perigemmal cells are the exclusive progenitors for taste buds cells, as proliferating cells are observed only around taste buds, and then appear to become post-mitotic, enter the taste bud as immature taste cells, and differentiate, as they move from the border region into the central region of taste buds [25-27,29]. For example, immature type II taste cells are born at least 2-3 days before they express specific type II cell markers [30,31]. …”

Postnatal Development of Membrane Excitability in Taste Cells of the Mouse Vallate Papilla

“…As shown in Figure 11 A, gustducin-IR was distributed throughout the cytoplasm of taste cells (Boughter et al, 1997;Cho et al, 1998; Figure 9. Inactivation of voltage-dependent K ϩ current (I K ) in Na/OUT cells.…”

“…After they were rinsed in 0.1 M PB, whole-mount preparations were immersed in a secondary antibody, a fluorescein isothiocyanate (FI TC)-conjugated anti-rabbit IgG (1:100; Vector Laboratories, Burlingame, CA) in 0.1 M PB for 12 hr at 40°C. Specificity of the immune reaction was assessed according to previous studies (Boughter et al, 1997;Cho et al, 1998). Immunofluorescence was examined using a Nikon TE 800 fluorescence microscope and also with a Bio-Rad Laser Scanning Microscope Radiance Plus (Bio-Rad, Hemstead Herts, UK).…”

“…Electronic images from the confocal microscope were processed using Adobe Photoshop 5.0 (Adobe Systems, Mountain View, CA). Immunocytochemical data were analyzed according to previous studies (Boughter et al, 1997;Cho et al, 1998).…”