Development and Patterning of the Cochlea: From Convergent Extension to Planar Polarity

International audienceWithin the mammalian cochlea, sensory hair cells and supporting cells are aligned in curvilinear rowsthat extend along the length of the tonotopic axis. In addition, all of the cells within the epithelium are uniformly polarized across the orthogonal neural–abneural axis. Finally, each hair cell is intrinsically polarized as revealed by the presence of an asymmetrically shaped and apically localized stereociliary bundle. It has been known for some time that many of the developmental processes that regulate these patterning events are mediated, to someextent, bythe core planarcell polarity (PCP)pathway. This article will reviewmore recent work demonstrating how components of the PCP pathway interact with cytoskeletal motor proteins to regulate cochlearoutgrowth. Finally, a signaling pathwayoriginally identified for its role in asymmetric cell divisions has recently been shown to mediate several aspects of intrinsic hair cell polarity, including kinocilia migration, bundle shape, and elongation