progenitor cells

https://www.pnas.org/content/117/24/13552

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

Role of Yap/Tead transcription factor complex in maintaining inner ear progenitors during development: new strategies to induce sensory cell regeneration

View ORCID ProfileKsenia Gnedeva, View ORCID ProfileXizi Wang, Melissa M. McGovern, Matthew Barton, Litao Tao, Talon Trecek, View ORCID ProfileTanner O. Monroe, Juan Llamas, Welly Makmura, James F. Martin, Andrew K. Groves, Mark Warchol, and View ORCID ProfileNeil Segil
PNAS June 16, 2020 117 (24) 13552-13561; first published June 1, 2020 https://doi.org/10.1073/pnas.2000175117

Edited by Marianne E. Bronner, California Institute of Technology, Pasadena, CA, and approved April 21, 2020 (received for review January 6, 2020)

Significance
While Yap/Tead signaling is well known to influence tissue growth and organ size during development, the molecular outputs of the pathway are tissue- and context-dependent and remain poorly understood. Our work expands the mechanistic understanding of how Yap/Tead signaling controls the precise number of progenitor cells that will be laid down within the developing inner ear to ultimately regulate the final size and function of the sensory organs. We also provide evidence that restoration of hearing and vestibular function may be amenable to YAP-mediated regeneration. Our data show that reactivation of Yap/Tead signaling after hair cell loss induces a proliferative response in vivo—a process thought to be permanently repressed in the mammalian inner ear.

Abstract
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.