Scientists have identified two proteins that pair up at the precise location in the ear where sound vibrations are turned into electrical signals. The finding may eventually help researchers develop more precise treatments for hearing loss, a condition that affects more than 32 million people in the United States.
When a car horn honks or someone laughs, sound vibrations travel through the air until they reach your ear and bounce against the eardrum, triggering a chain of events that is perceived as sound. Researchers have tried to learn exactly how the motion energy of sound is transformed into electrical impulses that the brain can understand. They knew that sensory cells in the inner ear called hair cells are crucial to the process.
Sitting atop the hair cells are tiny bristly structures known as stereocilia. As hair cells move in response to sound, their stereocilia bump up against a membrane, causing them to tilt. Microscopic tethers called "tip links" connect rows of shorter stereocilia at their tips to taller stereocilia behind them. The researchers report that two proteins already associated with hearing loss unite and adhere to one another to form the tip link.
Now that they understand what the tip link is made of and what conditions are required to assemble it, the team can study what it may take to rejoin tip links. Therapies that reunite the proteins may one day help to restore hearing in people with some forms of hearing loss.
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