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Dr. Edwin Stone, Associate Professor of Ophthalmology, at the Molecular Ophthalmology
Laboratory, University of Iowa, provided us with this press release describing some of their genetic research relating to macular degeneration.
Ul researchers map gene for eye disease linked to macular degeneration.
IOWA CITY, Iowa -- Researchers at the University of lowa College of Medicine have mapped the gene for a form of age-related
macular degeneration, a finding that may provide scientists with valuable insight into the leading cause of blindness in older Americans.
The Ul team led by Drs. Edwin Stone,
Associate Professor of Ophthalmology, and Val Sheffield, Associate Professor of Pediatrics, worked with colleagues from Arizona, West Virginia, Canada and Switzerland to map the gene
responsible for the disorder, known as malattia leventinese, to chromosome 2. The work is a major step in that this gene may also be involved in some cases of typical age-related
macular degeneration (AMD) -- a condition which affects many older adults. The Ul study is published in the Feb. 5 issue of the ournal Archives of Ophthalmology.
"Although
we do not yet know what percentage of AMD is caused by the gene or genes involved in malattia leventinese, the clinical features of this disorder are more similar to common forms of
AMD than any other hereditary macular disorders whose genes have been mapped or actually identified," Stone says. "This study is a significant step toward actually isolating
a gene for macular degeneration."
Gene mapping is the process of identifying the general location of a gene on a specific chromosome. Eventually, researchers hope to
isolate and sequence the gene itself to learn how it works. Macular degeneration is a term used to describe a variety of diseases in which the area of the retina at the center of the
back of the eye - called the macula - deteriorates, causing a loss of central vision. These disorders include common conditions such as AMD as well as rarer eye dystrophies that occur
at an earlier age. The genes for several of these dystrophies have been mapped previously and, in some cases, actually identified. However, none of the identified genes have been
found to cause a large number of macular degeneration cases that occur late in life.
A key characteristic of AMD is the presence of drusen, a random pattern of tiny
yellow-white spots in the macula. In patients with malattia leventinese, however, the drusen are arranged in a radial pattern, making it distinct from other types of AMD.
In
the Ul project, researchers studied 86 people from four unrelated families with radial drusen to identify the chromosomal location of the disease-causing gene. One family live in the
United States and the other three live in the Leventine Valley in southern Switzerland, where malattia leventinese was first described by ophthalmologists in 1925. Genealogical
studies revealed that the American family had two branches, one in Arizona and one in West Virginia, that have lived in the United States since the late 1700s. The Swiss families all
originated from the Leventine Valley and members of one family had participated in previous studies of malattia leventinese.
"It's interesting that the two branches of the
American family, who live a huge distance apart, show less genetic variation than the three Swiss families, who live in a very small geographic area," Sheffield says.
The
genetic characteristics of the people studied are more compatible with the diagnosis of AMD than any other previously mapped macular dystrophies. As a result, the gene responsible for
people with malattia leventinese has a good chance of also being involved in a significant number of AMD cases. "Mapping the gene gets us closer to identifying the gene involved
in typical AMD," Stone says. "And identifying the gene would be an important advance. It would facilitate the development of laboratory studies looking at the cellular and
biochemical processes involved in macular degeneration, which clinical studies of human patients cannot do. Also, the information we've learned from this study can be used to evaluate
other macular dystrophies for a possible genetic relationship. |
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