Brian C. Capell

N6 -methyladenosine (m 6 A) is the most abundant modification on messenger RNAs (mRNAs) and is catalyzed by methyltransferase-like protein 3 (Mettl3). To understand the role of m 6 A in a self-renewing somatic tissue, we deleted Mettl3 in epidermal progenitors in vivo. Mice lacking Mettl3 demonstrate marked features of dysfunctional development and self-renewal, including a loss of hair follicle morphogenesis and impaired cell adhesion and polarity associated with oral ulcerations. We show that Mettl3 promotes the m 6 A-mediated degradation of mRNAs encoding critical histone modifying enzymes. Depletion of Mettl3 results in the loss of m 6 A on these mRNAs and increases their expression and associated modifications, resulting in widespread gene expression abnormalities that mirror the gross phenotypic abnormalities. Collectively, these results have identified an additional layer of gene regulation within epithelial tissues, revealing an essential role for m 6 A in the regulation of chromatin modifiers, and underscoring a critical role for Mettl3-catalyzed m 6 A in proper epithelial development and self-renewal.