Clarin‐2 is essential for hearing by maintaining stereocilia integrity and function

• Main Authors: Lucy A Dunbar, Pranav Patni, Carlos Aguilar, Philomena Mburu, Laura Corns, Helena RR Wells, Sedigheh Delmaghani, Andrew Parker, Stuart Johnson, Debbie Williams, Christopher T Esapa, Michelle M Simon, Lauren Chessum, Sherylanne Newton, Joanne Dorning, Prashanthini Jeyarajan, Susan Morse, Andrea Lelli, Gemma F Codner, Thibault Peineau, Suhasini R Gopal, Kumar N Alagramam, Ronna Hertzano, Didier Dulon, Sara Wells, Frances M Williams, Christine Petit, Sally J Dawson, Steve DM Brown, Walter Marcotti, Aziz El‐Amraoui, Michael R Bowl
• Format: Article
• Language: English
• Published: Wiley 2019-09-01
• Series: EMBO Molecular Medicine
• Subjects: hair cells; mechanotransduction; mouse models; mutagenesis; stereocilia
• Online Access: https://doi.org/10.15252/emmm.201910288
• ISSN: 1757-4676; 1757-4684

Abstract Hearing relies on mechanically gated ion channels present in the actin‐rich stereocilia bundles at the apical surface of cochlear hair cells. Our knowledge of the mechanisms underlying the formation and maintenance of the sound‐receptive structure is limited. Utilizing a large‐scale forward genetic screen in mice, genome mapping and gene complementation tests, we identified Clrn2 as a new deafness gene. The Clrn2clarinet/clarinet mice (p.Trp4* mutation) exhibit a progressive, early‐onset hearing loss, with no overt retinal deficits. Utilizing data from the UK Biobank study, we could show that CLRN2 is involved in human non‐syndromic progressive hearing loss. Our in‐depth morphological, molecular and functional investigations establish that while it is not required for initial formation of cochlear sensory hair cell stereocilia bundles, clarin‐2 is critical for maintaining normal bundle integrity and functioning. In the differentiating hair bundles, lack of clarin‐2 leads to loss of mechano‐electrical transduction, followed by selective progressive loss of the transducing stereocilia. Together, our findings demonstrate a key role for clarin‐2 in mammalian hearing, providing insights into the interplay between mechano‐electrical transduction and stereocilia maintenance.