Update on Glaucoma Genetics
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While great progress has been made in identifying the underlying genetic components of glaucoma, there is still a lot of ground to cover before we have a complete picture of the many different genes that cause glaucoma, contribute to its severity, or affect treatment outcomes.
As research groups around the world are carrying out the search for glaucoma genes, each new discovery draws additional research groups into the study of the genes that are found. With more than a dozen genetic locations known for genes that can cause a broad array of different kinds of glaucoma, and more than a half dozen of the genes themselves identified, it is clear that most glaucoma genes remain to be found.
For primary open-angle glaucoma, of special importance because it affects so many people, there are now eight mapped gene locations, and two of those genes (MYOC and OPTN) have been shown to account for a small fraction of open-angle glaucoma cases. Many more regions around the genome have been identified that appear to be predictive of risk for primary open-angle glaucoma, called genetic risk factors, but the actual genes involved have not been found.
In addition, among the several congenital glaucoma genes that have been found, the CYP1B1 gene has been found to be responsible for more than half of cases of congenital glaucoma in some populations studied.
The identification of the first two open-angle glaucoma genes, MYOC and OPTN, and the first congenital glaucoma gene, CYP1B1, has provided important means to develop diagnostic tools and explore the mechanisms by which these genes participate in the initiation and progression of the glaucoma disease process. Biochemical and cell biology studies are examining the role of these three genes in cellular and developmental processes.
Genetic studies are evaluating how large a role each of these genes plays in different populations. Future studies are expected to examine the roles of such glaucoma genes in populations that have participated in some of the largest glaucoma clinical trials studies, in an effort to determine whether genetic testing might help predict not only whether someone will develop glaucoma, but also perhaps predict things about the clinical course of the disease or even the optimal treatment for that particular patient.
As a preliminary part of such clinical trials studies, the Glaucoma Research Foundation is currently supporting a study of family history of glaucoma in the population participating in the Collaborative Initial Glaucoma Treatment Study.
Since family history is already one of the pieces of information that physicians obtain during an eye examination, it will be important to determine whether such information can predict more than risk of glaucoma and perhaps also give the ophthalmologist important information that will assist in discussing prognosis and in suggesting the optimum treatment.
Article by Julie Richards, PHD and Paul R. Lichter, MD.
Julia E. Richards, PhD is Associate Professor of Ophthalmology and Visual Sciences, Associate Professor of Edidemiology at the University of Michigan.
Paul R. Lichter, MD is the F. Bruce Fralick Professor of Ophthalmology and Visual Sciences Director, University of Michigan Kellogg Eye Center.
Last reviewed on December 23, 2011