Fig. 5.

Loss of SOX2 in K14⁺ progenitors blocks fate acquisition of taste and non-taste epithelial cells. (A) In control FFP, K14⁺ progenitors (green) are limited to the basal epithelial layer, and are adjacent to taste buds (K8, magenta). (B) Two days after Sox2 deletion in K14^CreERT2/+;Sox2^flox/flox (SOX2cKO) mice, K14⁺ cells are found in suprabasal epithelial layers and have expanded around K8⁺ taste buds (arrowheads). (C,D) By 7 and 11 days post-SOX2cKO, K14⁺ cells comprise most of the FF epithelium, and many of these cells have enlarged cell somata with elongated processes (red arrows). (E) Control non-taste epithelium is characterized by basally located K14⁺ progenitors and filiform papillae (arrows; asterisks mark each filiform papilla core), interspersed with K14⁻ interpapillary (IPP) regions. The white bar spans the epithelium from the basement membrane to the superficial cellular layers (73 μm). (F) Filiform papillae are initially evident two days after SOX2cKO, but K14⁺ cells are uncharacteristically detected in suprabasal layers. (G,H) At 7 (G) and 11 (H) days after SOX2cKO, filiform papillae are no longer evident, K14⁺ cells span the entire thickness of the epithelium (white bars), and many K14⁺ cells have atypical morphologies (red arrows). Scale bars: 50 µm.