High Sox2 expression predicts taste lineage competency of lingual progenitors in vitro

Taste buds on the tongue are collections of taste receptor cells (TRCs) that detect sweet, sour, salty, umami and bitter stimuli. Like non-taste lingual epithelium, TRCs are renewed from basal keratinocytes, many of which express the transcription factor SOX2. Genetic lineage tracing has shown SOX2+ lingual progenitors give rise to both taste and non-taste lingual epithelium in the posterior circumvallate taste papilla (CVP) of mice. However, SOX2 is variably expressed among CVP cells suggesting that their progenitor potential may vary. Using transcriptome analysis and organoid technology, we show highly expressing SOX2+ cells are taste-competent progenitors that give rise to organoids comprising both TRCs and lingual epithelium, while organoids derived from low-expressing SOX2+ progenitors are composed entirely of non-taste cells. Hedgehog and WNT/ß-catenin are required for taste homeostasis in adult mice, but only WNT/ß-catenin promotes TRC differentiation in vitro and does so only in organoids derived from higher SOX2+ taste lineage-competent progenitors. Circumvallate papilla epithelial cells from 4 bins of Sox2GFP brightness were sorted using FACS and subjected to RNA-seq. Three replicates comprising of 7-13 mice per replicate were performed.