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July 22, 2004 FFB-Sponsored Research Reveals a New Gene Linked to Age-Related Macular Degeneration, reports The New England Journal of Medicine
For the second time in less than a year, researchers funded by The Foundation Fighting Blindness have made an important gene discovery that advances understanding of the causes of age-related macular degeneration (AMD). The new discovery involves a gene known as fibulin 5. Mutations in this gene were discovered among a group of patients with AMD. No one in an age-matched control group carried the same mutations. The discovery helps pave the way for preventive strategies and cures for AMD. A report of the discovery appears in the current (July 22, 2004) issue of The New England Journal of Medicine.
The mission of The Foundation Fighting Blindness (FFB) is to drive the research that will provide preventions, treatments and cures for people affected by retinal degenerative diseases. FFB, headquartered in Owings Mills, Maryland, has raised more than $200 million since it was founded in 1971.
The relationship between fibulin 5 and age-related degeneration was discovered
by Edwin M. Stone, M.D., Ph.D., and a team of researchers at the FFB-supported
Research Center for Macular Degeneration at the University of Iowa. Dr.
Stone is the Center’s director and the study’s lead author.
He is a professor of ophthalmology and visual sciences at UI, a Howard Hughes
Medical Institute investigator, and an FFB Scientific Advisory Board member.
Age-related macular degeneration affects over 9 million people in the U.S.
It is the most common cause of irreversible vision loss in the Western world,
and affects those 50-plus. Discoveries such as Stone’s—and an
earlier discovery of the hemicentin-1 gene by Dr. Dennis Schultz and colleagues
at Oregon Heath & Science University—reveal that AMD is probably
an umbrella term describing a larger group of related conditions. More AMD-related
genes will likely be discovered, and these will be added to a growing list
of risk factors for AMD such as cigarette smoking, sun exposure, and fatty
diet.
AMD is a degenerative disorder affecting a portion of the retina called the macula. The macula is responsible for clear, central vision. People with AMD have difficulty with activities like reading, watching television, and seeing faces of people directly across the table. Peripheral vision usually remains intact.
Fibulin 5 appears to play a role in the formation of tiny protein and fat-containing droplets, called drusen, in a thin layer (Bruch’s membrane) under the macula. Many eye specialists consider drusen a predictor of AMD. Stone and his group believe that there may be a link between the fibulin 5 gene, fibers of Bruch’s membrane, and drusen because the fibulin 5 gene is normally involved in the production of a protein called elastin, which is present in Bruch’s membrane fibers.
How did the researchers find that the fibulin
5 gene is involved in AMD?
They compared DNA in blood samples from 402 patients who had been diagnosed with AMD, to a nearly equal number of age-matched control subjects without AMD. The DNA was screened for mutations in five different members of the fibulin family of genes. It was only in the fibulin 5 gene that mutations were found solely in AMD patients.
Although the mutations occurred in only seven of the 402 patients, the finding is statistically significant. When extrapolated to the whole U.S. population with AMD, mutations in fibulin 5 could account for between 100,000 to 150,000 cases of AMD in the US alone.
The fibulin 5 finding is a genetic clue that researchers will use to understand the causes of AMD and for developing treatments and preventive strategies for patients whose gene tests reveal that they may be at risk. Finding genetic and environmental causes of AMD will be important to today’s baby boomers who are approaching a vulnerable age for AMD.
Timothy Schoen, Ph.D., director of The Foundation Fighting Blindness’ medical therapy program, believes that, “the finding by Dr. Stone and his group is a significant step. We are seeing that AMD is not a disease with a single cause and FFB is working closely with researchers to further our understanding.”
Funding by the Foundation has led to earlier discoveries of genes responsible for macular degeneration, including the 2003 discovery of the hemicentin-1 gene and the 1997 discovery of the ABCR gene for Stargardt disease, a juvenile form of macular degeneration. The Foundation Fighting Blindness (www.FightBlindness.org) is the largest non-governmental source of funding for retinal degenerative disease research in the world. Diseases such as macular degeneration, retinitis pigmentosa, and Usher syndrome affect more than 9 million Americans. The Foundation Fighting Blindness (FFB) is ranked as a “Top-Rated” charity by the American Institute of Philanthropy. FFB was named by Worth Magazine as one of the Best 100 Charities in the country.
© 2003-2005
The University of Iowa Center for Macular Degeneration
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