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Macular degneration gene identified.
Researches have found that a variation in a single gene could be responsible for 1/2 of all cases of age-related macular degeneration, researchers said on Thursday in a finding that could lead to better treatment for a leading cause of blindness.
This could lead to new treatment options for AMD
Three separate teams of scientists all pinpointed a gene called CFH for complement factor H. It is involved in a component of the immune system that regulates inflammation.
"This adds a major piece to the jigsaw puzzle in understanding age-related macular degeneration," said Stephen Daiger of the Human Genetics Center at the University of Texas Health Sciences Center in Houston.
"No one today can tell you exactly how this will contribute to a treatment. But I bet you a bunch that this will lead to a treatment some day," Daiger, who commented on the three studies for the journal Science, said in a telephone interview.
Age-related macular degeneration affects between 10 million and 15 million people in the United States alone and is the leading cause of blindness among the elderly.
By the age of 75, as many as 30 percent of Americans have some symptoms of the condition.
The macula is a circular area at the center of the retina and is packed with cones, the structures that help in seeing color, detect motion and making out fine detail.
As part of the normal aging process, yellowish waste deposits called drusen accumulate around the macula, but in AMD, they are bigger and there are more of them. They kill cells in the eye, affecting central vision.
Smoking, obesity, and a high-fat diet are all known to raise the risk of AMD, while eating fruits and vegetables lowers the risk. But there is also a genetic component.
"We know that one of the most significant factors in determining who gets macular degeneration is family history," said ophthalmologist Dr. Albert Edwards of the University of Texas Southwestern Medical Center, who led one of the studies.
The three teams at Yale University, Rockefeller University in New York, Duke University in North Carolina, UT Southwestern and elsewhere scanned gene maps and the DNA sequences of people with AMD and their relatives. All three groups homed in on CFH.
"This is the first study to identify a common variant of the specific gene being associated with AMD," said Yale's Josephine Hoh, who led another of the studies.
"Caucasian AMD patients are at least four times more likely to have one particular alteration in the CFH gene that produces a different form of the CFH protein compared to individuals without the disease," Hoh added in a statement.
Daiger said it will be easy to test people for this gene variant. The teams used different gene tests.
AMD takes decades to develop but Daiger said researchers can look at samples taken from people decades ago for other studies and test them for the CFH mutation.
Other scientists can create animal models such as mice with the CFH mutation and use them to study the disease and potential treatments, he said.
People who know they are at high risk can make sure they watch their diet and quit smoking, he said. "It's another reason to have a healthy lifestyle but we knew that," Daiger said.
And some treatments that affect the complement system could be tested -- for instance steroids such as dexamethasone or prednisone.
"For that matter even simple non-steroidal anti-inflammatory drugs like aspirin can damp down the complement system," Daiger said. "The question is whether any of them will have any effect on age-related macular degeneration."