Researchers at the Translational Genomics Research Institute, Phoenix, working with scientists from Los Angeles and Belgium, have identified a gene that could help explain why some people lose their hearing as they age.

In a study released online in the journal Human Molecular Genetics, researchers identified a gene that could help lead to the treatment of presbycusis, or age-related hearing loss, which accounts for 30% of all deafness, says a statement released by TGen. Research at TGen, a nonprofit organization, is focused on helping patients with diseases such as cancer, neurological disorders, and diabetes.

“Finding the genetic causes of age-related hearing loss could lead to treatments that would bring relief to millions of people worldwide who now suffer from social isolation, depression, and even cognitive impairment as a result of not being able to properly understand what others are saying,’’ said Matthew Huentelman, PhD, an investigator in TGen’s Neurogenomics Division and one of the scientific paper’s lead authors.

Researchers at TGen, the Los Angeles-based House Ear Institute, and the University of Antwerp, Belgium, said they believe the paper’s findings represent important and significant progress in the efforts to discover the origins of presbycusis.

“This is the first ever and largest genome-wide association study for age-related hearing loss,” said Rick Friedman, MD, PhD, another lead author who also is a principal investigator at the House Ear Institute and surgeon at the House Clinic. Scientists at the House Ear Institute, a nonprofit organization, investigate the cellular and molecular causes of hearing loss and related auditory disorders and neurological processes pertaining to the human auditory system and the brain.

The study uncovered several genes, but one gene stands out and is believed to put people at risk for hearing loss as they age. The research team believes a common variant in the GRM7 gene may be associated with susceptibility to glutamate excitotoxicity and hearing loss. It is the overexpression of glutamate that causes damage to the inner and outer hair cells in the inner ear leading to age-related hearing loss.

“We have known for a long time that genes play an important role in presbycusis. But until now, genetic research has lagged behind compared to other important diseases,” said Guy Van Camp, director of the Hereditary Deafness Laboratory and professor, University of Antwerp, Belgium. “The identification of GRM7 is a very exciting result, as it may provide insights in the development of the disease.”

The study participants were Caucasian, ages 53 to 67, and the samples were collected at eight centers in six nations throughout Europe from population registries or audiological consultations. The team of investigators analyzed the samples and identified genetic risks. In the lab, the research team scored markers across the entire genome of more than 2,000 samples.

Friedman said the next step is developing a laboratory model to test pharmaceuticals for possible treatment of presbycusis in the future.

The Hereditary Deafness Laboratory, a research group headed by Van Camp, has localized and identified many genes for different forms of hereditary deafness over the last 15 years. Most of the work was based on purely genetic forms of deafness. Over the past couple of years, the laboratory has started with the analysis of complex forms of hearing impairment such as presbycusis and noise-induced hearing impairment, which are caused by a complex interplay between environmental factors, such as noise or exposure to toxic substances or medication, and genes that make people susceptible.

[Source: Translational Genomics Research Institute]