New hearing mechanisms exposed


Rebecca Pool

Wednesday, April 24, 2019 - 13:00
Image: STED shows ring-like structures of cytoskeletal proteins in inner ear hair cells. [Zhuojia Liu, School of Creativity and Art at ShanghaiTech University]
Using super-resolution fluorescence microscopy, researchers from ShanghaiTech University, China, and colleagues, have revealed a previously unseen cytoskeleton structure within inner ear hair cells that is critical to hearing.
Stimulated emission depletion (STED) imaging detailed ring-like structures of cytoskeletal proteins wrapped around the base of so-called stereocilia rootlets.
Professor Zhong Guisheng and colleagues are certain that these structures play a key role in hearing development, with the latest images shedding new light on how hair cells can affect hearing.
Stereocilia are hair-like structures within inner ear hair cells that grow in early foetal development and detect sound by converting sound vibrations into neural signals.
However, hair cell dysfunction is one of the most common genetic causes of hearing loss.
To better understand how these cells affect hearing and deafness, Guisheng and colleagues used STED microscopy to image the inner hair cells of mice.
As Guisheng writes in Science Advances: “Stereocilia are inserted into the cuticular plate of hair cells by parallel actin rootlets, where they convert sound-induced mechanical vibrations into electrical signals.”
“The molecules that support these rootlets and enable them to withstand constant mechanical stresses underpin our ability to hear,” he adds. “However, the structures of these molecules have remained unknown.”
Imaging revealed the arrangement of cytoskeletal protein - spectrin - at the base of stereocilia rootlets.
Super-resolution fluorescence imaging reveals a previously unseen structure of cytoskeleton in inner ear hair cells. [[Zhuojia Liu, School of Creativity and Art at ShanghaiTech University]
Crucially, mouse studies also showed that damage to these spectrin ring-like structures of spectrin was associated with hearing loss. 
The researchers believe that the elasticity of spectrin is critical to the long-term survival of stereocilia under constant mechanical stress.
Research is published in Science Advances.
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