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Release: June 1, 1999

Gene is identified that causes specific form of macular degeneration

IOWA CITY, Iowa -- Researchers with University of Iowa Health Care have made an important breakthrough in the effort to find the genetic cause of age-related macular degeneration (AMD), the most common cause of blindness in developed countries.

The researchers have identified the gene that causes a specific form of macular degeneration that was first recognized 100 years ago. The UI team worked with scientists from Switzerland, Australia, Canada, Northern Ireland and England to study 39 families affected with the disease, known in different countries as Malattia Leventinese (ML), Doyne honeycomb retinal dystrophy (DHRD), or simply radial drusen.

The research team was led by Edwin M. Stone, M.D., Ph.D., UI professor of ophthalmology and the visual sciences. "One surprising aspect of the study," Stone said, "is that all 39 families appear to be related to one another through a common ancestor who lived thousands of years ago."

Patients with AMD have yellow-white deposits, known as drusen, that form beneath the retina. Patients with a mutation in this newly discovered gene also develop drusen, which makes this the first time that a specific genetic cause for these deposits has been identified.

Researchers say they can now use this discovery to jump-start their search for other genes that cause more common forms of age-related macular degeneration. Val C. Sheffield, M.D., Ph.D., UI professor of pediatrics, is another senior member of the Iowa research team. "The retina and the other tissues around it are very complicated structures in which tens of thousands of genes are expressed," Sheffield said. "Now that we have found that mutations affecting this specific, extracellular matrix protein that can cause drusen, we can narrow the search and speed up our efforts to find additional genes that cause a larger fraction of AMD."

Another important result of the discovery is that transgenic mice with alterations in this gene can now be created. The researchers believe that such animals will prove to be very helpful in the search for treatments that can prevent drusen from forming.

The UI research team's findings appear in today's issue of Nature Genetics. The report is titled, "A Single EFEMP1 Mutation Associated With Both Malattia Leventinese and Doyne Honeycomb Retinal Dystrophy."

(EDITOR'S NOTE: Edwin Stone can be reached for comment at (319) 354-2261).