m⁶A-Mediated Regulation of p63 by the METTL16-IGF2BP2 Axis Governs Epithelial Stem Cell Function and Epidermal...

The transcription factor p63 is indispensable for epithelial stem cell proliferation/differentiation and epidermal development, with alterations in the p63 pathway underlying a subset of ectodermal dysplasias. Despite its critical role, the mechanisms regulating p63 expression remain poorly understood. Here, we identify an m⁶A-mediated posttranscriptional mechanism controlling the expression of ΔNp63, the predominant functional p63 isoform in epidermal basal cells. We found that Cre-mediated conditional deletion of Mettl16, encoding a conserved m⁶A methyltransferase, in mouse epithelial basal cells caused severe skin developmental abnormalities, reminiscent of human ectodermal dysplasias. RNA sequencing revealed significant downregulation of ΔNp63 and its target genes in Mettl16-deficient skin, which linked METTL16 to p63 pathways. Mechanistically, we demonstrated that METTL16 directly binds to ΔNp63 mRNA to mediate its m⁶A modification; this modified ΔNp63 mRNA is subsequently recognized by the m⁶A reader IGF2BP2, which stabilizes ΔNp63 mRNA and thereby modulates its protein levels. Critically, restoration of ΔNp63 expression mitigated the epidermal defects in Mettl16-deficient mice. Collectively, our findings uncover a novel METTL16-m⁶A-IGF2BP2-ΔNp63 regulatory axis governing epidermal development, providing insights into the etiology of ectodermal dysplasias.