High-resolution images, simulations of the inner ear offer insights into hearing loss

Using X-ray crystallography, a group of scientists at Ohio State University (OSU), US, have managed to produce atomic-level maps of very fine filaments inside our ears that help with sound and balance. The tiny filaments are attached to the top of microscopic hairs that in turn sit on top of hair cells inside the inner ear – called tip links; they enable electrical signals between the ear and the brain, enabling us to hear and more.

Scientists have previously produced low-resolution images of tip links, and know that they are made of a pair of proteins called cadherin-23 and protocadherin-15, which are linked to inherited deafness. But with the high-resolution images of tip links by OSU comes a new understanding of how the cadherin-23 and protocadherin-15 proteins interact, described as a “molecular handshake.”

“If you don’t have the tip link, you can’t hear, and you can’t balance,” said OSU associate professor of chemistry and biochemistry Marcos Sotomayor. “They are essential.”

All the parts of our ears are designed to transform sound waves into electrical signals for our brains to process. The hearing process which includes the outer ear, middle ear, and inner ear happens in only a few millionths of a second, but if any part of the system fails, the sound signal either becomes muddled or does not reach the brain at all.

The science community will be able to learn more about why this is, or more specifically, why tip links fail, and investigate ways to prevent it from happening by observing a simulated model that mimics the complex dynamics of tip links as they respond to sound-generated forces.

“Now we can try to understand what is happening with the tip links when you have these sites modified by mutations, not only by looking at the static structures but also at the simulated trajectories of tip links responding to sound,” Sotomayor added.

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