Figure 7: SNEC harbors stem cells that mediate tissue homeostasis in a crypt-like pattern.

A) Long-term clonal tracing (28 wks) in Sox2-Confetti mice demonstrates clonal fixation (single color) in rete pegs (n=3 mice/timepoint). B) Example images of clonal forms (color patches) identified during 1–28 wks of lineage tracing. A reference rotated xy-image of a rete peg is shown to orient the individual xz-planes demonstrating the fate-mapping. “Tip” and “mid” describe lowest and middle height in the rete peg, respectively. C) Quantification of clone stratification between tip, casing, and core domains demonstrates no correlation in clone size between tip and casing compartments, suggesting that progenitor cells in these compartments function independently. Tip and core clone sizes are correlated (coeff = 0.74). The axes denote the fraction of the compartment that is occupied by the analyzed clone. D) Diagram of predicted progenitor cell populations in the rete peg. E) A good fit is obtained by superimposing the theoretical 1d scaling form to an invariant mean-scaled histogram (P_n(t)) of the mean-normalized tip clone sizes (n(t)). Tracing data are stratified by the chase duration (1–4 wks). This demonstrates scaling behavior in the evolution of tip clone sizes, consistent with neutral drift dynamics in tip progenitor population. F) Fit of neutral drift model to the empirical normalized mean tip clone size over time (λ/N²=0.02 /wk), consistent with replacement dynamics of an equipotent progenitor cell population. See also Figures S12–S14.