A new study, published on March 3, 2013 as an “Advance Online Publication” by the journal Nature Genetics, has identified seven new regions of the human genome (i.e., the complete set of genes contained in the human body) that are associated with an increased risk for age-related macular degeneration (AMD). Nature Genetics publishes current genetic research, with an emphasis on the genetic basis for common and complex diseases.
About the Research
The study, entitled Seven new loci associated with age-related macular degeneration, was authored by the AMD Gene Consortium, with Lars G. Fritsche as lead author. (Note: “Loci” is the plural of “locus” or “location” and refers to the seven new regions/locations, scattered throughout the human genome on many different chromosomes, that are associated with increased risk for AMD.) The complete list of contributors and their affiliations can be found at the Nature Genetics site.
The AMD Gene Consortium is a network of international investigators, representing 18 research groups, supported by the United States National Eye Institute (NEI), a part of the National Institutes of Health. The Consortium’s large-scale analysis includes data from more than 17,100 people with the most advanced and severe forms of AMD, which were compared to data from more than 60,000 people of European and Asian ancestry without AMD. The Consortium also confirmed 12 loci that were identified in previous studies.
The current study, which represents the most comprehensive genome-wide analysis to date of genetic variations associated with AMD, was made possible by a number of prior genetic research breakthroughs, including immune system research and AMD risk, the Human Genome Project, and the International HapMap Project.
More about the Study
From an NEI press release:
“Like a map that identifies neighborhoods where the electricity has been knocked out by a storm, the AMD Gene Consortium’s study effectively tagged regions within the genome where researchers are most likely to find short circuits in DNA that cause AMD,” said Anand Swaroop, Ph.D., chief of the NEI Laboratory of Neurobiology and Neurodegeneration and Repair, and one of the group leaders of this consortium effort.
“Once you are in the right neighborhood, going block-to-block or house-to-house to look for downed power lines goes much faster. Likewise, by limiting their search to the 19 genomic regions identified by the AMD Gene Consortium, scientists can search more efficiently for specific genes and causative changes that play a role in AMD.”
Macular Degeneration: What are the Mechanisms?
From Risk Factors for Age-Related Macular Degeneration at VisionAware.org:
Age and the environmental factors together produce an increased number of free radicals in the macula. The macula is the small sensitive area in the center of the retina that provides clear central vision. Free radicals are unstable molecules that must be neutralized to keep them from causing damage. Mother Nature has provided anti-oxidants in food to neutralize these free radicals.
However, when we have too many free radicals and not enough anti-oxidants, damage is done. The first signs of damage in the macula are small whitish or yellowish spots called drusen, which the ophthalmologist can see usually before the individual is experiencing vision loss.
This initial damage triggers inflammation, which causes more damage, exacerbated by more free radicals. This results in more inflammation and the cycle continues, eventually scarring the macula and causing central vision loss.
The Study Results and Conclusions
The National Eye Institute summarized the study results as follows:
As with other common diseases, such as type 2 diabetes, an individual person’s risk for getting AMD is likely determined not by one, but by many, genes. Further comprehensive DNA analysis of the areas around the 19 loci identified by the AMD Gene Consortium could turn up undiscovered rare genetic variants with a disproportionately large effect on AMD risk. Discovery of such genes could greatly advance scientists’ understanding of AMD pathogenesis and their quest for more effective treatments.
“This compelling analysis by the AMD Gene Consortium demonstrates the enormous value of effective collaboration,” said NEI Director Paul A. Sieving, M.D., Ph.D. “Combining data from multiple studies, this international effort provides insight into the molecular basis of AMD, which will help researchers search for causes of the disease and will inform future development of new diagnostic and treatment strategies.”
Additional Information
VisionAware will continue to provide updates for ongoing genetic and macular degeneration research as they become available. You can read more information about genetic risk factors for AMD at A Nationwide Study Is Investigating Genetic and Other Risk Factors for Macular Degeneration on the VisionAware blog.
Save Your Vision Month
This March, during Save Your Vision Month, visit VisionAware.org to learn more about normal vision changes as we grow older, the difference between a vision screening and an eye examination, the different types of eye care professionals, and questions to ask during an eye examination.