Otic placode cell specification and proliferation are regulated by Notch signaling in avian development

Background: The entire inner ear including the cochlear-vestibular ganglion arises from a simple epithelium, the otic placode. Precursors for the placode originate from a pool of progenitors located in ectoderm next to the future hindbrain, the pre-otic field, where they are intermingled with future epibranchial and epidermal cells. While the importance of secreted proteins, such as FGFs and Wnts, in imparting otic identity has been well studied, how precursors for these different fates segregate locally is less well understood. Results: (1) The Notch ligand Delta1 and the Notch target Hes5-2 are expressed in a part of pre-otic field before otic commitment, indicative of active Notch signaling, and this is confirmed using a Notch reporter. (2) Loss and gain-of-function approaches reveal that Notch signaling regulates both proliferation and specification of pre-otic progenitors. Conclusions: Our results identify a novel function of Notch signaling in cell fate determination in the pre-otic field of avian embryos. Developmental Dynamics 244: 839-851, 2015. (C) 2015 Wiley Periodicals, Inc.