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| |  Gene That Causes Glaucoma Has Been Located SAN FRANCISCO, Jan. 30, 1997 - As reported in the January 31st issue of the journal "Science," researchers have located a gene that causes a subset of Primary Open Angle Glaucoma (POAG) called juvenile open angle glaucoma. Juvenile open angle glaucoma is characterized by its early onset. Glaucoma is the second leading cause of blindness in the United States. The disease, characterized by progressive deterioration of the optic nerve, is generally associated with elevated intraocular pressure. POAG is the most common form of glaucoma, affecting 3 million Americans. "The identification of this gene could increase our understanding of the pathophysiology of the disease. These researchers have identified a mutation in approximately 3% of adult-onset (POAG) glaucoma patients they tested," said Tara Steele, Executive Director of the Glaucoma Research Foundation. Identification of the glaucoma gene provides the possibility of developing accurate and inexpensive methods for testing those who may be predisposed to develop glaucoma, and could lead to more effective treatments. The scientists in Iowa led by Drs. Edwin Stone, Val Sheffield and Wallace L. Alward found the genetic mutation in some individuals who did NOT have the juvenile form of the disease. This suggests that the mutations of the gene lead to the development of both the juvenile and the adult form of glaucoma. The researchers in Iowa lead used a genetic approach to identify this glaucoma gene. Meanwhile, researchers in San Francisco (with support from the Glaucoma Research Foundation) cloned the same gene using a different approach. The combined data from the two groups demonstrates that this gene causes glaucoma. The Glaucoma Research Foundation, a national non-profit organization was a principal funding source for the work of Drs. Thai Nguyen and Jon Polansky at the UCSF medical school campus who were contributing authors to the Science article. "This research takes us one step closer to a day when glaucoma patients can be identified from tissue (blood) samples and medications can be designed according to a genetic template," said John Hetherington, M.D., Vice President Glaucoma Research Foundation Thai Nguyen, Ph.D -- a molecular biologist at the University of California at San Francisco was the first to clone the gene. Based on his knowledge on the gene he has proposed its potential role in obstructing the outflow of fluid from the eye. Because of its relationship to the Trabecular meshwork (the eye's drainage system) he called it TIGR (Trabecular Meshwork-Induced Glucocorticoid Response protein). The San Francisco lab was trying to understand the cell biology and pathology of steroid-induced glaucoma and along the way the two groups realized that they were studying the same gene. Iowa's data provided evidence that the TIGR molecule is involved in the genetic inheritance of glaucoma. The Iowa group used a genetic approach to show there was a defect affecting 3% of the adult glaucoma population. They were using families with glaucoma to map where in the human genome the gene was. They narrowed the location and then identified a gene within the interval that was causing the disease. Once they did that they knew which gene sequence was involved. They also knew from its sequence that it was the same gene that San Francisco lab was studying. "Besides Ed Stone's group in Iowa, who proved the genetic importance of the TIGR molecule in glaucoma by using our TIGR sequence, we anticipate that other groups around the world who are working on a similar genetic location of the TIGR gene will confirm that this gene is an important factor in glaucoma. "And we predict that they will come up with similar or new mutations affecting glaucoma," said Thai Nguyen, Ph.D. "We would soon be able to develop guidelines that recommend that people be screened for this particular genetic defect. Those who carry the defect in this gene would be likely to get glaucoma and should be followed carefully by their ophthalmologists," said Tara Steele. "The ability to diagnose a subset of people with a predisposition to glaucoma before they have standard signs of the disease (high pressure or optic nerve damage) -- most importantly, before they lose sight could be a huge benefit to their long-term treatment," she added. "Dr. Nguyen and I believe that we are on the verge of a major breakthrough in glaucoma research and possibly therapy. Now that there is clear `proof of principle' that the TIGR gene is involved in glaucoma based on the report by Stone and Sheffield. "Our independent indications are that this gene could help in the diagnosis of more than just the 3% reported in the article, which may just be the tip of the iceberg. Having a defect in the TIGR gene will indicate a 'risk-factor' for glaucoma," said Jon R. Polansky, Associate Professor, Ophthalmology and hormone research, UCSF "For the patients who have mutations in this gene we hope to be able to determine which of their children will develop glaucoma and which of their children are at no higher risk for glaucoma than the general population. "My hope is that this is the first of many discoveries on the genetics of POAG that will revolutionize the way we think about this disease," said Wallace L.M. Alward, M.D., University of Iowa Department of Ophthalmology. "This is a very important finding because it opens up an important new area for study. We don't know whether this protein is involved only in 3% of adult POAG or whether it will have broader implications," said David Epstein, M.D., Chair, Scientific Advisory Committee, Glaucoma Research Foundation. The Glaucoma Research Foundation is a registered 501c3 charity. Individuals may contact the Foundation for information on glaucoma, its diagnosis, treatments and latest research developments. Call toll free 1-800/826-6693 or visit www.glaucoma.org .
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