Vangl2 acts in distinct cell types to establish bidirectional hair-bundle polarity and maintains tissue-wide alignment in zebrafish neuromasts

Abstract

The conserved core planar cell polarity (PCP) pathway orients cells and subcellular structures within an epithelium through asymmetric protein localization and intercellular communication. In vestibular organs and lateral-line neuromasts, mechanosensory hair cells are interspersed among support cells and form opposing hair-bundle orientations along a shared axis, enabling bidirectional sensitivity to head motion and water flow, respectively. In zebrafish neuromasts, Notch-mediated lateral inhibition gives rise to two hair-cell populations, distinguished by differential Emx2 expression, that orient their cell-intrinsic polarity machinery differently relative to a PCP-dependent tissue-wide axis. However, it remains unclear how PCP proteins are organized across hair cells and support cells to achieve both opposing hair-bundle orientations and tissue-wide alignment, and whether PCP signaling remains required after hair-bundle polarity is established. Combining quantitative spatial mapping of the core PCP protein Vangl2 with cell-type-specific and temporally controlled protein degradation, we show that hair cells and support cells make distinct yet coordinated contributions to the polarized Vangl2 organization within neuromasts and to bidirectional hair-bundle polarity. Support-cell Vangl2 facilitates tissue-wide alignment of hair bundles along the anteroposterior axis, whereas hair-cell Vangl2 is required to generate opposing hair-bundle orientations along this axis. Vangl2 degradation after hair bundles have formed disrupts their tissue-wide alignment, showing that planar polarity is actively maintained rather than fixed after establishment. Together, these findings reveal how Vangl2-dependent PCP signaling is distributed across distinct cell types within a heterogeneous epithelium to generate opposing polarity outcomes and remains necessary to preserve tissue-level planar organization.