A prevalent Krt8-to-Krt5 cellular state transition in skin is co-opted by p63 for enamel organ development

Tooth enamel, the hardest tissue in vertebrates, is crucial for mastication and dental protection. Its formation depends on the enamel organ (EO), a specialized epithelial structure derived from oral epithelium. A fundamental question persists: how does uniform oral epithelium differentiate into diverse EO cell types? While p63, a master regulator of ectodermal development, coordinates multiple signaling pathways essential for dental placode formation, its specific roles in EO development remain unclear due to the early developmental arrest in p63 knockout mice. Using single-cell RNA sequencing data from mouse incisors, we demonstrate that p63 is expressed across all EO cell types, serving both shared and distinct functions. Through trajectory reconstruction, we identify the role of p63 in regulating both amelogenic (AmG) and non-AmG lineage commitment during EO development. Our comparative transcriptome analyses reveal that p63 regulates the Krt8-to-Krt5 transition during AmG cell differentiation, paralleling its function in skin development. This parallel is reinforced by comparative motif discovery, revealing shared transcription factor usage, particularly p63 and AP-2 family members, in both AmG and skin epidermal cells during this transition. Chromatin accessibility analysis further illustrate that p63 mediates this transition through chromatin landscape remodeling. Together, these findings demonstrate that p63 co-opts the Krt8-to-Krt5 transition mechanism from skin development for EO development, providing novel insights into the molecular mechanisms underlying EO development and potential therapeutic targets for enamel disorders.