NIH-funded research provides framework for future studies of AMD biology, therapy
MARSHFIELD – Marshfield Clinic patients’ genetic samples were used in an international study that has significantly expanded the number of genetic factors known to play a role in age-related macular degeneration (AMD), a leading cause of vision loss among people age 50 and older.
Supported by the National Eye Institute (NEI), part of the National Institutes of Health, the findings may help researchers understand the biological processes that lead to AMD, and may make it possible to identify new therapeutic targets for potential drug development.
AMD is a progressive disease that causes the death of the retinal photoreceptors, the light-sensitive cells at the back of the eye. The most severe damage occurs in the macula, a small area of the retina needed for sharp, central vision necessary for reading, driving and other daily tasks.
Currently no Food and Drug Administration-approved treatments exist for the more common form of advanced AMD, called geographic atrophy or “dry” AMD. While therapies for the other advanced form, neovascular or “wet” AMD, can successfully halt the growth of abnormal, leaky blood vessels in the eye, the therapies do not cure the condition, nor do they work for everyone.
A combination of genetic, environmental and lifestyle risk factors causes AMD. Up to this point, researchers had identified 21 regions of the genome – called loci – that influence the risk of AMD. The new research, published in Nature Genetics, brings the number up to 34 loci.
The International AMD Genomics Consortium, which includes 26 centers worldwide, collected and analyzed genetic data from 43,566 people to systematically identify common and rare variations in genetic coding – called variants –associated with AMD.
Marshfield Clinic patients comprised one of the largest groups in this international study. The Clinic provided DNA samples from people with and without AMD, including age- and gender-matched cases and controls, and samples from the oldest people without AMD. The patients’ personal information was removed from the data so they can’t be identified.
“This is the most comprehensive study to date that has uncovered both common and rare variants associated with AMD risk,” said Murray Brilliant, Ph.D., director, Marshfield Clinic Research Foundation Center for Human Genetics. “We can now design tests that can reveal a person’s risk of developing AMD. That is very important as one of our other recent studies suggests we may have a drug that can delay or prevent AMD. This gives us hope that someday we can identify at-risk patients and treat them with a drug to prevent the disease.”
For the first time the researchers also identified a variant specific to the neovascular form of AMD, which may point to reasons why therapy for this form of AMD is effective for some people but not everyone.
“Even with the pooling of genetic information from such a large population, the variants identified by the international consortium still cannot account for all of the heritability of AMD,” said Grace L. Shen, Ph.D., a group leader and director of the retinal diseases program at NEI. “We are, however, on track for discovering important variant genes that may play a role in AMD heritability.”
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Marshfield Clinic Research Foundation (MCRF), a division of Marshfield Clinic, was founded in 1959. It’s the largest private medical research institute in Wisconsin. MCRF consists of research centers in clinical research, agricultural health and safety, epidemiology, human genetics, biomedical informatics and dental informatics. Marshfield Clinic investigators publish extensively in peer-reviewed medical and scientific journals addressing a wide range of diseases and other health issues, including cancer, infectious diseases, heart disease, diabetes, eye disease, neurological disease, pediatrics, radiology, women’s health, agricultural safety and genetics.