Maintenance and turnover of Sox2(+) adult stem cells in the gustatory epithelium

Continuous turnover of taste bud cells in the oral cavity underlies the homeostasis of taste tissues. Previous studies have demonstrated that Sox2(+) stem cells give rise to all types of epithelial cells including taste bud cells and non-gustatory epithelial cells in the oral epithelium, and Sox2 is required for generating taste bud cells. Here, we show the dynamism of single stem cells through multicolor lineage tracing analyses in Sox2-CreERT2; Rosa26-Confetti mice. In the non-gustatory epithelium, unicolored areas populated by a cluster of cells expressing the same fluorescent protein grew over time, while epithelial cells were randomly labeled with multiple fluorescent proteins by short-term tracing. Similar phenomena were observed in gustatory epithelia. These results suggest that the Sox2(+) stem cell population is maintained by balancing the increase of certain stem cells with the reduction of the others. In the gustatory epithelia, many single taste buds contained cells labeled with different fluorescent proteins, indicating that a single taste bud is composed of cells derived from multiple Sox2(+) stem cells. Our results reveal the characteristics of Sox2(+) stem cells underlying the turnover of taste bud cells and the homeostasis of taste tissues.