Dr. Marci Lesperance, associate professor of pediatric otolaryngology, and Sarah Emery, a research laboratory specialist, have discovered that a mutation in a gene on chromosome 12, SLC17A8, accounts for a form of hearing loss that diminishes one's ability to hear high-frequency sounds.
The researchers say that the loss may occur early or later in life, and that the severity of the mutation's effects varies among individuals.
Since the exact mutation was found in two families that were completely unrelated, the researchers believe that it may be an ancient one and not particularly rare.
Dr. Lesperance says that future research may find that this mutation affects others who have an unexplained family history of hearing loss.
The researchers have even named the inherited form of deafness DFNA25.
They consider it to be significant for further research because it closely resembles the hearing loss common in people as they age, called presbycusis.
"Some people with the mutation have hearing loss in their 40s of the kind we normally see in people a decade or more older. Often, identifying a gene in individuals who have early onset of a disorder will help explain why the disorder occurs in the general population," says Dr. Lesperance.
Meanwhile, a French scientist named Jean-Luc Puel has demonstrated that a mouse would go deaf when the SLC17A8 gene was knocked off.
The researchers have also discovered that the SLC17A8 gene and the protein it encodes, VGLUT3, are needed in the inner ear to process the hearing signal.
Dr. Lesperance hopes that the research will encourage families and physicians to be alert to the possibility that hearing problems are inherited, which may spur more people to take prompt action such as frequent hearing tests in the young and early use of hearing aids, as well as genetic counselling to understand the chances of occurrence in future children.
"In many types of hereditary hearing loss, it's likely that environmental factors that people can control, such as smoking and exposure to noise, also can influence how severe the hearing loss is, and how early in life it begins," says Dr. Lesperance.
The study has been published online in the American Journal of Hearing Genetics.