Extended Data Fig. 2: Additional human immunohistochemistry of basal cell populations.

Co-staining for SOX2, Ki67 or the HBC marker TP63. Proliferative activity has been used as a hallmark of the globose basal cell (GBC) phenotype. We reasoned that, although some proliferating cells in the olfactory epithelium (OE) might be immune or inflammatory cells, proliferative cells within the GBC layers of the OE that are SOX2⁺/Ki67⁺/TP63^- would be categorized as GBCs. a, Sustentacular cell nuclei at the top of the OE are SOX2-bright; and horizontal basal cells (HBCs) and a subset of GBCs are SOX2⁺, although less intensely. Arrow marks a SOX2⁺/KI67⁺ cell among the proliferative KI67⁺ basal region, consistent with the GBC phenotype. b, SOX2 co-localizes with TP63 in HBCs; arrows mark Sox2⁺/TP63^- GBCs. c, TP63 + HBCs are mitotically quiescent, while many GBCs are actively proliferating, often in scattered cell clusters. Arrow marks a cluster of KI67⁺/TP63^- basal cells. Dashed line indicates basal lamina. Immunostaining for a-c was conducted in triplicate with similar results. Scale bar, 50 µm.