p53 is a critical regulator of airway epithelial progenitor cell homeostasis.

How progenitor cells regulate quiescence and differentiation is poorly understood. Here, we demonstrate that the tumor suppressor p53 regulates both proliferation and differentiation of club progenitor cells in the airway epithelium. We show that p53 loss decreases ciliated cell differentiation and increases the proliferative capacity of club progenitors, increasing epithelial cell density. p53 deficient progenitors generated a pseudostratified epithelium containing basal-like cells in vitro and contained an increased proportion of BASCs in vivo, suggesting that p53 suppresses multipotency during homeostasis. Conversely, an additional copy of p53 decreases proliferation and increases ciliated cell differentiation. Using single cell RNA-Seq, we expose heterogeneity within airway epithelial progenitor cells and found that cell cycle regulators, particularly p21, are altered following p53 loss. Together, these findings reveal an essential role for p53 in regulating progenitor cell behavior, which has broad implications in understanding both stem cell and cancer biology