Organ of Corti size is governed by Yap/Tead-mediated progenitor self-renewal.

Precise control of organ growth and patterning is executed through a balanced regulation of progenitor self-renewal and differentiation. In the auditory sensory epithelium-the organ of Corti-progenitor cells exit the cell cycle in a coordinated wave between E12.5 and E14.5 before the initiation of sensory receptor cell differentiation, making it a unique system for studying the molecular mechanisms controlling the switch between proliferation and differentiation. Here we identify the Yap/Tead complex as a key regulator of the self-renewal gene network in organ of Corti progenitor cells. We show that Tead transcription factors bind directly to the putative regulatory elements of many stemness- and cell cycle-related genes. We also show that the Tead coactivator protein, Yap, is degraded specifically in the Sox2-positive domain of the cochlear duct, resulting in down-regulation of Tead gene targets. Further, conditional loss of the Yap gene in the inner ear results in the formation of significantly smaller auditory and vestibular sensory epithelia, while conditional overexpression of a constitutively active version of Yap, Yap5SA, is sufficient to prevent cell cycle exit and to prolong sensory tissue growth. We also show that viral gene delivery of Yap5SA in the postnatal inner ear sensory epithelia in vivo drives cell cycle reentry after hair cell loss. Taken together, these data highlight the key role of the Yap/Tead transcription factor complex in maintaining inner ear progenitors during development, and suggest new strategies to induce sensory cell regeneration.