Troy/Tnfrsf19 marks epidermal cells that govern interfollicular epidermal renewal and cornification

The skin epidermis is a highly compartmentalised tissue consisting of a cornifying epithelium called the interfollicular epidermis (IFE) and associated hair follicles (HFs). Several stem cell populations have been described that mark specific sub compartments in the skin but none of them is IFE-specific. Here we identify Troy as a marker of IFE and HF infundibulum basal layer cells in embryonic and adult human and mouse epidermis. Genetic lineage-tracing experiments demonstrate that Troy-expressing basal cells contribute to long-term renewal of all layers of the cornifying epithelium. Single-cell transcriptomics and organoid assays of Troy-expressing cells as well as their progeny confirmed stem cell identity as well as the ability to generate differentiating daughter cells. In conclusion, we define Troy as a marker of epidermal basal cells that govern interfollicular epidermal renewal and cornification. Overall design: We generated single-cell and bulk transcriptome data from epidermal keratinocytes collected from adult murine skin epidermis.