Extended Data Fig. 3: Prenatal skin epidermal cell composition and comparison with adult hair follicles.

(a) Schematic of stages of HF formation. (b) Dot plot showing variance-scaled, mean expression (dot colour) and percent of expressing cells (dot size) of DEGs between gestational stage groups (grouped PCW) (right) and expression of the same genes by different epithelial cell states in prenatal skin (left). (c) Bar plot showing the average proportions of stromal cell states across gestational age in prenatal skin. Bar colours represent cell states. (d) Heatmap showing the correspondence (measured by Jaccard index) between prenatal skin/SkO (y-axis) and adult (x-axis) epidermal and HF cell states from a logistic regression model trained on adult HF data¹¹, projected onto integrated prenatal skin/SkO data. (e) UMAPs showing clustered cell states in integrated data from adult HFs¹¹ and prenatal/SkO, coloured by prenatal skin/SkO cell types (left) and adult cell types (right). (f) Volcano plot showing differentially expressed genes between prenatal matrix cells and adult matrix cells using Wilcoxon rank-sum, two-sided, Benjamini-Hochberg adjusted¹¹. (g) Percentage of FOXP3 coverage in HF regions and non-HF regions across five prenatal skin samples. Data are mean ± SD and statistics (p = 0.0131) generated with an unpaired t-test. (h) Immunostained human prenatal skin at 15PCW for Tregs with FOXP3 (red; red arrows), epithelial keratinocytes with Keratin 14 (yellow) and dermal papilla with SOX2 (cyan; cyan arrows). Scale bar: 100 µm. Tregs, Regulatory T cells. For details on statistics and reproducibility, see Methods. The images in a were created using BioRender (https://biorender.com).

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