The Il1r2-CreERT2 knock-in mouse enables inducible labeling of slow-cycling epidermal basal cells and genetic ablation of the IL-1 decoy receptor

The interfollicular epidermis is maintained by spatially organized basal cell populations with distinct molecular signatures and division kinetics; however, the markers that define these populations remain poorly defined. In this study, we identified Il1r2, which encodes the IL-1 decoy receptor IL-1R2, as a marker of the slow-cycling basal population in the epidermis. Single-cell RNA-seq analysis of epidermal and hair follicle basal populations in the murine tail skin revealed that Il1r2 is preferentially expressed in the slow-cycling epidermal basal population, and immunofluorescence staining confirmed its protein localization in tissues. To enable fate mapping of this population, we generated an Il1r2-CreERT2 knock-in mouse line using a CRISPR-Cas9-based PITCh method. Tamoxifen induction in Il1r2-CreERT2/Rosa-tdTomato mice exhibited selective labeling of basal cells localized to the slow-cycling interscale region of the tail epidermis. Because the CreERT2 cassette was inserted into the Il1r2 coding sequence, homozygous Il1r2-CreERT2 knock-in mice can also serve as an Il1r2 knockout model through targeted gene ablation. Thus, the Il1r2-CreERT2 mouse line provides a dual genetic tool for lineage tracing of the slow-cycling epidermal basal population and for functional modulation of IL-1 signaling in vivo.