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, 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.
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 September 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.
We are excited to be hosting Drs. Young and Farber at our 9th World Symposium, “Where Vision Meets Reality” in San Diego from November 16 – 18. They will be among 19 leading vision and genetic eye researchers who will meet to share and collaborate on their latest research efforts involving genetic vision disorders. Click here for more information on the Symposium.