DNP63 regulates epithelial stratification and differentiation in the murine ureter

The urothelium is a stratified epithelium that lines the inner surfaces of organs in the urinary drainage system. It has a layered composition of basal, intermediate, and large superficial cells. The process, by which this cytoarchitecture develops from uncommitted precursor cells, is not well understood. In this study, we analyzed the cellular and molecular functions of the transcription factor DNP63 in urothelial development in the murine ureter. DNP63 expression begins in epithelial progenitors of this organ at embryonic day (E)14.5 and is confined to basal and intermediate cells from late fetal stages onward. In mice with a conditional loss of DNp63 in the epithelial progenitors, the ureteric urothelium presented as a folded monolayer composed predominantly of partially differentiated superficial cells around birth. At E15.5, the proliferation and division planes of epithelial cells remained unaffected. However, genes essential for cell adhesion and division in other epithelial stratification programs were downregulated, as were genes involved in basal and intermediate cell differentiation. In contrast, Ihh expression in the epithelium increased concomitantly with the premature formation of the lamina propria. Our results suggest that a conserved DNP63 gene regulatory module is responsible for epithelial stratification and the differentiation of basal and intermediate cells, as well as the timely differentiation of the lamina propria in fetal ureter development. The urothelial cytoarchitecture was progressively reconstituted in DNp63-deficient ureters after birth. This suggests that a few DNP63^þ epithelial progenitors, which have escaped recombination, can undergo rapid proliferative expansion and differentiation into intermediate and basal cells.