Researchers identify second gene that causes ocular albinism
The quest for better understanding and finding cures for ocular albinism is closer to fruition, thanks to the recent discovery of mutations in a second gene that can trigger this genetic vision disorder. This finding has major implications for better diagnosis of this disease. With a clearer understanding of the cause of the condition, scientists can move forward with cutting-edge research to improve vision for thousands of children with ocular albinism.
The research, funded by The Vision of Children Foundation based in San Diego, was led by Alejandra Young, Ph.D., Assistant Project Scientist at UCLA Stein Eye Institute. Dr. Young worked under the leadership of Debora Farber, Ph.D., Karl Kirchgessner Foundation Distinguished Professor of Ophthalmology and Director of the Retinal Biochemistry Laboratory.
The Vision of Children Foundation was founded by Rancho Santa Fe residents Sam and Vivian Hardage in 1991, after their son was born with ocular albinism. At the time, there were no researchers anywhere in the world studying this genetic vision disorder, for which there are no treatments and no cures. The Hardages were determined to encourage scientific research to find a cure for this congenital condition. Today, The Vision of Children Foundation is the foremost organization in the world supporting research for ocular albinism and related vision disorders.
Until recently, ocular albinism was believed to be caused solely by mutations in the OA1 gene (also known as GPR143), which provides instructions for making a protein that is involved in the pigmentation of the eyes and skin. This discovery was made in the early 1990s, also thanks to research funded by The Vision of Children Foundation.
“However, about 30 percent of patients with clinical manifestations of the disease had no mutations in the OA1 gene,” said Dr. Young. “This raised the possibility that a different gene could be responsible.”
Dr. Young and her colleagues analyzed DNA samples from 26 people who exhibit all the clinical characteristics of ocular albinism but do not have mutations in the OA1 gene. They compared these DNA samples to samples from subjects without a personal or family history of the disorder and consistently discovered several mutations in a gene called GNAI3. The results of this research study were published in the Sept. 8, 2016, edition of PLOS ONE, a multidisciplinary open access scientific journal.
Ocular albinism is a genetic eye disease that is transmitted through the X chromosome. It primarily affects the pigmentation in the eye, which is essential for normal vision. Affected individuals typically suffer from poor clarity of vision (reduced visual acuity), rapid and involuntary eye movements (nystagmus), eyes that do not look in the same direction (strabismus), and increased sensitivity to light (photophobia). They also have problems with the ability to create depth perception when combining vision from both eyes. This is due to abnormalities involving the optic nerves, which carry visual information from the eye to the brain.
Incidence rates for this disorder are difficult to determine, partly due to frequent misdiagnosis. The most common form of ocular albinism is known as the Nettleship-Falls or type 1, which affects at least 1 in 60,000 males in the United States, according to the National Institute of Health. The classic signs and symptoms of this condition are much less common in females, who are carriers. Unlike some other forms of albinism, ocular albinism usually does not significantly affect the color of the skin and hair.
Ocular albinism is just one of hundreds of genetic vision disorders. Millions of people around the world have uncorrectable genetic vision disorders, and even obtaining an accurate diagnosis is difficult, as there are limited facilities that can run the tests. Depending on the particular genetic disorder, testing can take up to two months to complete. One of the few centers conducting such tests is the Medical Genetics Laboratory at Baylor College of Medicine in Houston. Richard Alan Lewis, M.D., a collaborator on this research, specializes in the study and diagnosis of hereditary eye disorders at Baylor.
Over the past two decades, Vision of Children-funded researchers have conducted revolutionary work that has broad implications for vision science. Now, gene therapy and stem cell therapies, which seemed but a distant dream when the Foundation was founded, are becoming a reality. Scientists funded by the Foundation are exploring how to best use byproducts of patients’ own stem cells to replace defective DNA. This research is also taking place at UCLA Stein Eye Institute, under the direction of Farber.
“Our goal is to provide adequate funding to finish the quest at hand — eradicating Ocular Albinism,” Sam Hardage said. “Scientists should then be able to utilize these proven techniques and procedures as a template to discover cures for a variety of genetic vision disorders, including oculocutaneous albinism and retinal degenerations. “Through this research, we can foresee a day in the not-so-distant future when these and other vision diseases will be curable.”
The Vision of Children Foundation is a nonprofit 501(c)(3) charitable organization dedicated to curing hereditary childhood blindness and other vision disorders, and improving the quality of life of visually impaired children and their families. Visit www.visionofchildren.org; 858-314-7916.
Submitted press release
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