The tongue epithelium consists broadly of two main cell types: taste receptor cells (TRCs), found in taste buds; and non-taste lingual epithelial cells, which surround and support taste buds. Previous studies have shown that these cells are renewed from populations of SOX2+ and LGR5+ lingual progenitors found in the circumvallate taste papillae (CVP). Although LGR5+ progenitors are known to produce both taste and non-taste cells, SOX2 expression can vary greatly among progenitors and, thus, their contribution to taste bud cell lineage is unclear. In this study, Linda Barlow and colleagues investigate the effect of SOX2 expression on lingual epithelium lineage in the CVP of mice. Here, they show that higher expressing SOX2+ cells produce organoids containing both TRCs and non-taste lingual epithelium, although with a lower density of TRCs than from LGR5+ progenitors. Conversely, organoids derived from lower expressing SOX2+ cells fail to produce any TRCs. Furthermore, both the Hedgehog and Wnt/β-catenin signalling pathways have been implicated in taste homeostasis in mice. However, the authors find that perturbation of Wnt, but not Hedgehog signalling, impacts TRC differentiation in organoids derived from more highly expressing SOX2+ progenitors only. Together, these findings clarify the roles of SOX2+ lingual progenitors in taste bud cell lineage and exemplify lingual organoid technology as a useful tool for studying lingual epithelial homeostasis.
