Functional Cell Types in Taste Buds Have Distinct Longevities
Figure 6
EdU-labeled non-Type II, non-Type III cells enter the taste bud rapidly and constitute the largest fraction of EdU+ cells.
This heterogeneous group of cells is defined here simply by the absence of both PLCβ2 and 5HT. A, B, C, a taste bud from a mouse 3 days post-injection displays several EdU-labeled cells (arrowheads) of this class. EdU, KCNQ1, PLCβ2 and 5HT were visualized as in previous figures. The indicated EdU+ nuclei do not map onto immunoreactivity for either cell-type marker; but they are clearly within the taste bud perimeter. D, Aggregate data from 30 mice for EdU+, PLCβ2–, 5HT– cells, fit with a two-phase exponential decay curve. The faster component comprises 80% of the population and exhibits a half-life of 8 days while the slower component contains 20% of the EdU+,PLCβ2–,5HT– cells and disappears with a half-life of 24 days (R2 = 0.97). The exponential fit was ambiguous insofar as the relative fraction of the two sub-populations could not be discerned precisely. Equivalent goodness-of-fit was obtained for the fast component constituting 60–80% of the cellular population. The EdU+,PLCβ2–,5HT– cells are obviously a heterogeneous group as discussed in the text. Different constitutent cell types (e.g. mature Type I cells, immature taste cells, quiescent undifferentiated cells, and perhaps some progenitor cells) may all have dramatically different lifetimes. E, Incidence of these EdU+ PLCβ2– 5HT– cells among all EdU+ cells within the taste buds. As with other graphs, each symbol represents data from a separate mouse. Scale bar, 20 µm.