Gene Could Point to Macular Degeneration Treatment

Age-related macular degeneration (AMD) is the most common form of irreversible blindness in developed countries. AMD is a complex genetic disease, meaning several genes must be involved. Scientists have now pinpointed two of those genes, and they suggest new ways the disease may be treated.

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Scientist searching for genes that cause disease used to focus on disorders where a single gene was the culprit. But as the tools of molecular genetics have become more sophisticated, scientists have turned to diseases where multiple genes are involved. As NPR's Joe Palca reports, researchers are making some impressive headway in the genetics underlying the most common form of irreversible blindness in the developed world.

JOE PALCA reporting:

By some estimates, age-related macular degeneration, or AMD as it is known, affects 10 million people in the United States. In its severe form people lose the ability to see what's directly in front of them. It's as if somebody punched a hole right in the middle of your world. Reading, driving, watching TV become impossible. Last year four different teams all concluded that one gene call Compliment Factor H was definitely involved in the disease.

Rando Allikmets led one of the teams. He's at the Columbia University Medical Center in New York. He says Compliment Factor H gave his team a clue where to look for more genes.

Mr. RANDO ALLIKMETS (Columbia University Medical Center): We hypothesized that other genes and proteins in the same pathway should be involved in AMD.

PALCA: So Alexmetz and his colleagues focused on Compliment Factor B, and as he reports today in the online version of the journal Nature Genetics, sure enough Compliment Factor B was involved. The two genes each make a protein that plays a key role in fighting inflammation.

Mr. ALLIKMETS: These two proteins work together to keep the system well balanced and effective. So if one or the other does not perform their duties as they are supposed to, what happens is that inflammation lingers.

PALCA: And Alexmetz says the theory is that inflammation starts the damage in the back of the eye that ultimately leads to blindness. Albert Edwards is another gene hunter at the University of Texas Southwestern Medical Center in Dallas. He's also a doctor, and he sees patients with AMD. He says it's useful from a research standpoint to know what genes are involved in the disease.

Dr. ALBERT EDWARDS (University of Texas): But they don't actually have treatment impact right now. So for example, I would say to you, how are we going to manage patients differently if they have these genetic variations?

PALCA: And the answer is?

Dr. EDWARDS: The answer would be I don't know.

PALCA: But it does suggest where to target the search for new drugs. And knowing the genes involved in AMD may have another benefit. Jonathan Haines of Vanderbilt University in Nashville is also looking for AMD genes. In an upcoming article in the American Journal of Human Genetics, he details the role of a gene on chromosome 10. The article also shows how smoking can increase the risk for AMD in people who have a particular variant of that gene. Haines says by testing people's genes and finding out their smoking habits it may be possible to predict who will ultimately develop the disease.

Mr. JONATHAN HAINES (Vanderbilt University, Nashville): If we have such a good predictive model we may be able to identify individuals who might develop macular degeneration before they actually develop it and maybe be able to try some preventive treatment which has never been possible before. So it really opens up a whole new area of clinical research.

PALCA: Haines says if you know who is going to develop AMD, then you know the right people to test preventive treatments on.

Mr. HAINES: There really aren't any well-known or well-accepted preventive treatments, because we've never been able to do that kind of clinical prediction, and now we're at a stage where we will be able to do that.

PALCA: And Haines says you don't really have to prevent AMD, you just have to delay it. AMD mostly affects people over 65. If you could delay the onset by 30 or 40 years, that'd solve the problem for most of us. Joe Palca, NPR News, Washington.

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