Gene influencing age-related hearing loss
If you wonder why Gramps' hearing has gone to the dogs and Grandma's hearing has not -- well, there could be a plethora of reasons. Such as lifetime exposure to loud noises, certain meds, certain medical conditions and more. Add genes to the mix. In a study reported in the journal Human Molecular Genetics, researchers at the local House Ear Institute, in collaboration with scientists at several other institutions (see list below), found several genes involved in hearing loss risk, most notably one called GRM7.
GRM7 carries instructions for a protein that is made in cells of the inner ear and is involved in receiving signals from nerves. A nerve-signaling chemical called glutamate attaches to this protein receptor -- and too much glutamate stimulation can damage the fragile hair cells key to hearing. Certain people, it appears, have a gene that directs formation of a receptor that's more sensitive to such damage.
Scientists have actually known for some time that there's a significant genetic contribution to the decay of hearing loss that comes with age -- but it's one thing to know that genes exist, quite another to have tracked any of them down. These days, what with the whole human genome sequenced and high-tech "chips" available for the scanning of tiny variations that exist between one individual and the next, such genes are easier than ever to find.
The study was conducted by Rick Friedman of the House Ear Institute as well as others from House, the Translation Genomics Research Institute in Phoenix, Affymetrix in Santa Clara and the University of Antwerp, Belgium. It involved genetic scans of more than 800 Europeans with age-related hearing loss and a similar number of people without it, for comparison.
By the way, hair cells are very pretty. You can learn more, and see a cool image, here (and also learn about the hope that one day hair cells could be regenerated).
Hair cells do their sound-transmitting job by moving in response to sound. Here's a bizarre movie one Brit scientist made of a hair cell dancing to "Rock Around the Clock." (Make sure you listen to the soundtrack.)
-- Rosie Mestel