Researchers Identify Gene in Age Related Hearing Loss
Editor: Researchers at the House Ear Institute (HEI) and affiliated
organizations have identified a gene that contributes to age-related
hearing loss. Here's the report from the folks at HEI.
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December 2008
Presbycusis, or age-related hearing loss, accounts for 30 percent of
all hearing loss. So, why do some people lose their hearing as they get
older but other people can still hear a pin drop?
The answer may be in a study released online in the journal Human
Molecular Genetics. Advance access is available online at http://hmg.oxfordjournals.org/papbyrecent.dtl.
"This is the first ever and largest genome-wide association study for
age-related hearing loss," said Rick Friedman, M.D., Ph.D., lead author
and House Ear Institute principal investigator and surgeon at the House
Clinic.
The study was conducted in collaboration with colleagues at the
Phoenix-based Translational Genomics Research Institute (TGen), Affymetrix
in Santa Clara, Calif., and the University of Antwerp, Belgium. It
uncovered several genes, but one gene stands out and is believed to put
people at risk for hearing loss as they age.
They discovered a common variant in the GRM7 gene, which the research
team believes 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.
"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 Dr. Matthew Huentelman, an investigator in TGen's
Neurogenomics Division and one of the lead authors.
Researchers believe this paper's findings represent important and
significant progress in the efforts to discover the origins of presbycusis.
"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 used Affymetrix GeneChip(r) Human Mapping
500K to score 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.
For more information, please visit the institute web site, http://www.hei.org.
About House Ear Institute
The House Ear Institute (HEI) is a non-profit 501(c)(3) organization
dedicated to advancing hearing science through research and education to
improve quality of life. HEI scientists investigate the cellular and
molecular causes of hearing loss and related auditory disorders as well as
neurological processes pertaining to the human auditory system and the
brain. Our researchers also explore technology advancements to improve
auditory implants, hearing aids, diagnostic techniques and rehabilitation
tools. The Institute shares its knowledge with the scientific and medical
communities as well as the general public through its education and
outreach programs. For more information about HEI please call (800)
388-8612 or visit http://www.hei.org.
About TGen
The Translational Genomics Research Institute (TGen) is a non-profit
organization dedicated to conducting groundbreaking research with life
changing results. Research at TGen is focused on helping patients with
diseases such as cancer, neurological disorders and diabetes. TGen is on
the cutting edge of translational research where investigators are able to
unravel the genetic components of common and complex diseases. Working
with collaborators in the scientific and medical communities, TGen
believes it can make a substantial contribution to the efficiency and
effectiveness of the translational process. For more information, visit:
http://www.tgen.org.
About the Hereditary Deafness Laboratory, University of Antwerp,
Belgium
This research group, headed by Prof. Guy Van Camp, has localized and
identified many genes for different forms of hereditary deafness over the
last 15 years. Most of this work was based on purely genetic forms of
deafness. Over the last couple of years, this laboratory has started with
the analysis of complex forms of hearing impairment such as presbycusis
and noise-induced hearing impairment. These types of hearing impairment
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. The laboratory has collected large numbers of samples,
and has developed new methodologies for the analysis of these diseases.
