Stiffness and tension gradients of the hair cell's tip-link complex in the mammalian cochlea

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Abstract

Sound analysis by the cochlea relies on frequency tuning of mechanosensory hair cells along a tonotopic axis. To clarify the underlying biophysical mechanism, we have investigated the micromechanical properties of the hair cell's mechanoreceptive hair bundle within the apical half of the rat cochlea. We studied both inner and outer hair cells, which send nervous signals to the brain and amplify cochlear vibrations, respectively. We find that tonotopy is associated with gradients of stiffness and resting mechanical tension, with steeper gradients for outer hair cells, emphasizing the division of labor between the two hair-cell types. We demonstrate that tension in the tip links that convey force to the mechano-electrical transduction channels increases at reduced Ca²⁺. Finally, we reveal gradients in stiffness and tension at the level of a single tip link. We conclude that mechanical gradients of the tip-link complex may help specify the characteristic frequency of the hair cell.

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All data generated or analysed during this study are included in the manuscript and supporting files. Source data files have been provided for Figures 2, 3, 5 and 6.

Article and author information

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Mélanie Tobin

Laboratoire Physico-Chimie Curie, PSL Research University, Paris, France

Competing interests
The authors declare that no competing interests exist.
Atitheb Chaiyasitdhi

Laboratoire Physico-Chimie Curie, PSL Research University, Paris, France

Competing interests
The authors declare that no competing interests exist.
Vincent Michel

Sorbonne Université, Paris, France

Competing interests
The authors declare that no competing interests exist.
Nicolas Antoine Michalski

Sorbonne Université, Paris, France

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0002-1287-2709
Pascal Martin

Laboratoire Physico-Chimie Curie, PSL Research University, Paris, France

For correspondence
pascal.martin@curie.fr

Competing interests
The authors declare that no competing interests exist.

"This ORCID iD identifies the author of this article:" 0000-0001-6860-4677

Funding

French National Agency for Research (ANR-11-BSV5-011)

Pascal Martin

Labex Celltisphybio part of the Idex PSL (ANR-10-LABX-0038)

Pascal Martin

French National Agency for Research (ANR-16-CE13-0015)

Pascal Martin

The funders had no role in study design, data collection and interpretation, or the decision to submit the work for publication.

Ethics

Animal experimentation: All experimental procedures were approved by the Ethics committee on animal experimentation of the Institut Curie; they complied with the European and French-National Regulation for the Protection of Vertebrate Animals used for Experimental and other Scientific Purposes (Directive 2010/63; French Decree 2013-118).

Copyright

This article is distributed under the terms of the Creative Commons Attribution License permitting unrestricted use and redistribution provided that the original author and source are credited.