Sensory perception in the inner ear relies on the hair bundle, the highly polarized brush of movement detectors that crowns hair cells. We previously showed that, in the mouse cochlea, the edge of the forming bundle is defined by the ‘bare zone’, a microvilli-free sub-region of apical membrane specified by the Insc-LGN-Gαi protein complex. We now report that LGN and Gαi also occupy the very tip of stereocilia that directly abut the bare zone. We demonstrate that LGN and Gαi are both essential for promoting the elongation and differential identity of stereocilia across rows. Interestingly, we also reveal that total LGN-Gαi protein amounts are actively balanced between the bare zone and stereocilia tips, suggesting that early planar asymmetry of protein enrichment at the bare zone confers adjacent stereocilia their tallest identity. We propose that LGN and Gαi participate in a long-inferred signal that originates outside the bundle to model its staircase-like architecture, a property that is essential for direction sensitivity to mechanical deflection and hearing.
The authors declare no competing or financial interests.
Conceptualization: B.T. and M.C.; Experimentation and data analysis: B.T., A.L.D.T. and N.D.; Manuscript writing: B.T.; Manuscript editing: M.C. and A.L.D.T.; Supervision and funding: B.T. and M.C.
This work was supported by a research grant from the Canadian Institutes of Health Research [MOP-102584] to M.C. and by a start-up from the Jackson Laboratory to B.T. B.T. was supported by a Human Frontiers Science Program long-term fellowship [LT 00041/2007-L/3] and M.C. is a Senior Fellow of the Fonds de la recherche du Québec–Santé/Fondation Antoine Turmel.
Supplementary information available online at http://dev.biologists.org/lookup/doi/10.1242/dev.139089.supplemental
- Received April 25, 2016.
- Accepted September 14, 2016.