Hippo signaling promotes Ets21c-dependent apical cell extrusion in theDrosophilawing disc

Abstract

ABSTRACTCell extrusion is a crucial regulator of epithelial tissue development and homeostasis. Epithelial cells undergoing apoptosis, bearing pathological mutations, and possessing developmental defects are actively extruded toward elimination. However, the molecular mechanisms ofDrosophilaepithelial cell extrusion are not fully understood. Here, we report that activation of the conserved Hippo (Hpo) signaling pathway induces both apical and basal cell extrusion in theDrosophilawing disc epithelia. We show that canonical Yorki targets Diap1, and that dMyc and Cyclin E are not required for either apical or basal cell extrusion induced by activation of this pathway. Another target gene,bantam, is only involved in basal cell extrusion, suggesting novel Hpo-regulated apical cell extrusion mechanisms. Using RNA-Seq analysis, we found that JNK signaling is activated in the extruding cells. We provide genetic evidence that JNK signaling activation is both sufficient and necessary for Hpo-regulated cell extrusion. Furthermore, we demonstrate that the ETS-domain transcription factor Ets21c, an ortholog of proto-oncogenesFLI1andERG, acts downstream of JNK signaling to mediate apical cell extrusion. Our findings reveal a novel molecular link between Hpo signaling and cell extrusion.SUMMARY STATEMENTActivation of Hippo signaling induces cell extrusion in theDrosophilawing epithelia, in whichbantammediates basal cell extrusion and Ets21c mediates apical cell extrusion.