Scientists have identified a gene that is "strongly associated" with a person's risk for developing age-related macular degeneration (AMD). The finding was made by three independent teams, which include researchers with the National Eye Institute (NEI), part of the National Institutes of Health (NIH), and other leading research centers. Detecting an AMD-associated gene may lead to early detection and new strategies for prevention and treatment for the debilitating eye disease. Papers by all three teams appear in a March 10, on-line issue of the journal Science (in Science Express ).
AMD is a disease that blurs or destroys sharp, central vision. There is no known cure for AMD. Most scientists think the cause lies in an interplay of hereditary and environmental factors. It is the leading cause of blindness in people over age 60.
Family history of AMD is a risk factor for the disease. In recent years, eye researchers have been investigating certain portions of chromosomes to find AMD-associated genes. The new studies provide the strongest evidence yet of a specific gene association.
"The three studies are a significant step in AMD research. They confirm a strong genetic component of AMD, which may allow scientists to develop tests for the disease before symptoms begin to appear and when therapies might help slow its progress," said Paul A. Sieving, M.D., Ph.D., director of the National Eye Institute.
The three studies described in Science used different methods to screen the genomes from different groups of AMD patients. Yet all three studies came up with a commonly inherited variant of the same gene, called complement factor H (CFH). The CFH gene is responsible for a protein that helps regulate inflammation in part of the immune system that attacks diseased and damaged cells. In certain patients with AMD, inflammation in the eyes may trigger a biological process leading to the disease.
"This exciting work helps clarify how AMD develops and the relationship of the immune system with the disease. This could lead to entirely new approaches for therapeutics," said Emily Chew, M.D., deputy director, NEI Division of Epidemiology and Clinical Research, and collaborator on one of the studies.
Dr. Chew's team, headed by Josephine Hoh, Ph.D., Yale School of Public Health, New Haven , CT , found that people whose genetic make up includes a variant of the CFH gene are 7.4 times more likely to develop AMD. The study was based on whole genome analysis of participants from the NEI-sponsored Age-Related Eye Disease Study, a major clinical study that closely followed nearly 5,000 patients with varying stages of AMD.
The team will next look at a larger number of patients and perhaps look at genetic differences between patients with the wet and dry forms of AMD. Wet AMD occurs when abnormal blood vessels behind the retina start to grow under the macula, a part of the central retina, where light is converted to nerve signals to the brain. Loss of central vision can be rapid. Dry AMD occurs when the light-sensitive cells in the macula slowly break down. Central vision can be lost gradually.
The second team, headed by Jonathan L. Haines, Ph.D., Vanderbilt University Medical Center , Nashville , identified the CFH gene by using high resolution mapping of a portion of a chromosome that had previously been associated with AMD in family studies.
A third research team, also funded by NEI, was headed by Albert O. Edwards, M.D., the University of Texas Southwestern Medical Center, Dallas.
Adapted from the following source: National Eye Institute