Mechano-signaling feedback underlies precise inner hair cell patterning in the organ of Corti
The mammalian hearing organ, the organ of Corti, is one of the most organized tissues in the mammalian body plan. It contains precisely positioned array of alternating sensory hair cells (HC) and non-sensory supporting cells that emerge during embryonic development from an initially disordered pro-sensory domain. While much is known on the genetics and biochemistry underlying this process, it is still unclear how such precise alternating patterns emerge during embryonic development. Here, we combine live imaging of mouse inner ear explants with hybrid mechano-regulatory models to elucidate the mechanisms underlying the formation of a single row of inner HC (IHC). We show that a narrow strip of initially disordered salt-and-pepper pattern, generated by Notch-mediated lateral inhibition, is dynamically refined by coordinated intercalations, delaminations, and differential adhesion. We identify a new morphological transition, termed hopping intercalation, that allows nascent IHC to hop under the apical plane into their final position. We further show that IHC patterning is associated with boundary localization of the cell adhesion molecules, Nectin-3 and Nectin-1. Our experimental results and modeling support a mechanism for precise patterning based on a feedback between Notch-mediated differentiation and mechanically driven cellular reorganization that is likely relevant for many developmental processes.