Genetic Study of Chinese Patients with Recessive RP Provides Global Benefits

June 20, 2013

A Foundation-funded investigative team led by Ruifang Sui, M.D., Ph.D., of Peking Union Medical College Hospital, has completed the first comprehensive genetic screening of a group of Chinese people with autosomal recessive retinitis pigmentosa (arRP). Results of the study, recently published in Investigative Ophthalmology and Visual Science, bolster the international research community’s genetic knowledge of the vision-robbing condition and reveal new targets for potential therapies. 

“Studying different ethnic populations reveals new genetic mutations, which helps us understand the mechanisms of retinal disease and associated vision loss,” says Radha Ayyagari, Ph.D., a retinal-disease genetic researcher at the University of California, San Diego. “This information is valuable in developing therapies.”  

China has one of the world’s largest RP populations with approximately 340,000 affected — more than triple the number of people with RP in the United States. Yet most previous genetic studies of RP have been performed on people of European descent. 

“We are very excited to be greatly expanding our global reach in genetic research,” says Stephen Rose, Ph.D., chief research officer, Foundation Fighting Blindness. “Studies of people with Chinese descent can significantly increase our knowledge base of rare retinal diseases, and what we learn from the Chinese can benefit those of other ethnicities and vice versa.”

Dr. Sui and her colleagues reported that 63 percent of the mutations identified in the study were previously unknown. The team’s findings were made using a probe that could detect mutations in 163 known retinal-disease genes, including those for arRP and several other retinal conditions.  

The investigators identified disease-causing mutations in 12 of 31 families. While all families were thought to have arRP based on doctors’ diagnoses, genetic screening revealed that three families had different retinal conditions.  

Two families had Bietti crystalline dystrophy (BCD) caused by mutations in the gene CYP4V2. BCD is more common among people of Asian descent and characterized by: crystals in the cornea; shiny, yellow deposits on the retina; and progressive degeneration of the retinal pigment epithelium. 

One family had cone-rod dystrophy (CRD) caused by mutations in the gene ADAM9. CRD affects central vision early in the disease process.

“This study underscores the importance of genetic screening for making a definitive diagnosis. Retinal diseases aren’t always as they appear. There are often surprises,” says Dr. Rose. 

Dr. Sui notes that the 19 undiagnosed families may be affected by mutations that are difficult to identify in known retinal-disease genes or defects in genes that have not yet been linked to retinal degenerations.