Tripotent Lgr5 stem cells in the posterior tongue generate non-taste lingual, taste and salivary gland cells [Bulk RNA-seq]

The circumvallate papillae (CVP) and foliate papillae (FoP) of the posterior tongue contain taste buds in close proximity to specialized salivary glands, known as von Ebner and minor salivary glands, respectively. The developmental relationship between taste buds and these salivary glands remains largely unexplored. Lineage tracing studies in mice have revealed that Lgr5 marks taste bud stem cells. Here, we report single-cell RNA sequencing of the entire CVP and FoP of mice, yielding transcriptional profiles of cells from tongue surface epithelium, taste buds and the associated salivary glands. We unveiled a developmental trajectory in which taste buds, the associated salivary glands and the non-taste tongue surface epithelium originate from a common Lgr5+ cell. We describe long-term organoid culture conditions for these cells and confirm their tripotency at the clonal level in vitro. CVP and FoP harbor chemosensory units consisting of taste bud and salivary gland cells derived from the same parental Lgr5+ stem cell. Overall design: Circumvallate papillae (n=20) and foliate papillae (n=40) were send for single-cell RNA seq. Lineage trajectory analysis revealed a potential bi/tripotent Lgr5+ stem cell in the posterior tongue. Subsequent scRNA-seq analysis of clonal cultures derived from a single Lgr5+ stem cell presented its tripotent nature. Next, in-vivo mulitcolour lineage tracing confirmed this phenomenon. Studying the cell fate decisions resulted in a putative role for Foxe1 in the lineage trajectory. Bulk RNA-sequencing of knock-out of Foxe1 in the posterior tongue organoids revealed an ablation of mature saliva markers and a more progenitor-like phenotype.