Can you tell the difference between high – and low –thread-count sheets just by touching them? Thank usherin, a protein found in an exceedingly mysterious structure in your fingertips. Usherin also helps us see and listen to, suggesting a deep molecular connection among our most vital senses. “The work is surprising,” says Ellen Lumpkin, a neuroscientist at the University of California (UC), Berkeley, who wasn’t involved in the study.
The study, she says, points to one protein being employed over and another time in distinct ways to assist us to monitor the surface world. Scientists already had some hints that usherin is very important for our sense of touch. A mutation within the gene that codes for it, USH2A, causes Usher syndrome—a rare, genetic disease that results in blindness, deafness, and an inability to feel faint vibrations within the fingertips.
To further explore usherin’s role up-to-date, researchers recruited 13 patients with a kind of Usher syndrome that specifically affects touch. The team—led by Gary Lewin, a neuroscientist at the life scientist Center for Molecular Medicine—measured how well every person sensed pain, temperature changes, and tiny vibrations at 10 and 125 hertz (Hz), mimicking the feeling of moving a fingertip across a rough surface. The scientists then compared the patients’ results against those of 65 healthy volunteers.
People with Usher syndrome did even as well as their counterparts at sensing temperature changes and mild pain, the team found. But they were fourfold less likely to choose informed the 125-Hz vibrations and 1.5 times less likely to detect the 10-Hz vibrations. To find out why, the researchers replicated the experiment using mice with or without the USH2A gene. like their human equivalents, rodents in both groups were fine at detecting temperature changes and pain. But mice with USH2A were better at detecting both degrees of vibrations than those without it, the team reports in the week in Nature Neuroscience.
The study also unveiled a surprising source for usherin. The protein is usually present in nerve cells to blame for vision and hearing. But in mice and humans, the scientists found it within the “Meissner corpuscle,” a microscopic, oval-shaped capsule that surrounds nerve cells in fingers. The find adds to an emerging area of research: exploring how molecules outside neurons, once thought to merely support or protect nerve cells, shape our sense of touch, says Theanne Griffith, a neuroscientist at UC Davis who wasn’t committed to the work.
Until about 20 years ago, she says, researchers thought these neurons were operating alone to expire sensory signals to the brain. “It’s amazing that they were ready to show these results,” Lewin says. He and his team commit to determine exactly how USH2A is functioning to assist us to detect vibrations, noting that further work with both the gene and protein may lead to a more robust understanding of how we gauge and control our grip strength. “We now have evidence that something being made within the Meissner corpuscle is important,” he says, “but there are likely more elements at play.”
Originally Published at Science Mag