The science team indicates it is the first naturally occurring case of a nonhuman primate model of the syndrome and could lead to potential treatments.
Researchers identified a mutated gene in three rhesus monkeys that is associated with Bardet-Biedl Syndrome (BBS), a rare genetic disease that causes childhood-onset blindness. The science team indicates it is the first naturally occurring case of a nonhuman primate model of the syndrome and could lead to potential treatments.
The disease also leads to kidney problems, polydactyly—extra fingers or toes—obesity, hypogonadism, and other symptoms. It occurs in about one in 140,000 to 160,000 births in North America.
“There is no cure for Bardet-Biedel Syndrome today, but having a naturally occurring animal model for the condition could help us find one in the future,” Martha Neuringer, professor of neuroscience at the Oregon National Primate Research Center at Oregon Health & Science University, told MedicalXpress.
The findings have broader implications than just BBS. BBS is part of a family of diseases called retinitis pigmentosa, a disease of the retina. This larger family of eye diseases affects about one in 3,500 to 4,000 people in the U.S. and Europe.
The research was published in the journal Experimental Eye Research.
The authors note, “The development of therapies for retinal disorders is hampered by a lack of appropriate animal models. Higher nonhuman primates are the only animals with retinal structure similar to humans, including the presence of a macula and fovea. However, few nonhuman primate models of genetic retinal disease are known.”
One of the first gene therapies approved for use is Spark Therapeutics’ Luxturna (voretigene neparvovec) for a rare, genetic form of blindness called retinal dystrophy. The eye is a good target for gene therapies because the therapies can be directly injected into the organ, rather than requiring a systemic approach.
The development of Luxturna was built on the discovery of a gene mutation in dogs in the 1990s linked to Leber’s congenital amaurosis, which causes blindness.
Neuringer’s research team hopes their discovery can lead to a similar therapy for BBS.
Neuringer and her research group identified two monkeys that were related and did not have cells key to vision. Colleagues Betsy Ferguson and Samuel Petersen than analyzed the monkeys’ genomes and found both had a mutation of the BBS7 gene, which is one of at least 14 genes associated with BBS.
Ferguson’s research has involved sequencing the genomes of 2,000 rhesus macaques at the nonhuman primate research center. She was then able to identify a third monkey with the same mutation. That monkey had serious vision loss when it was identified in 2018. At the time, the monkey was three-and-a-half years old, but it had adapted to its social group to such an extent that the blindness wasn’t obvious.
Neuringer and her group are using a National Eye Institute grant to breed more monkeys with the naturally occurring BBS7 mutations, which will provide researchers with more laboratory animals to work with to develop treatments for these diseases.
The BBS genes encode proteins for the function of cilia. Models of BBS have been developed from rodents, fish and roundworms, but they are not as closely related to human eyes as primate models.
One of the common symptoms of BBS in humans is obesity. However, in the monkeys, only one had a body weight considered higher than average. This could be related to other factors, including the development of kidney disease. One of the monkeys also has relatively smaller testicles, but with only three monkeys, it’s not clear if the mutation is behind these characteristics.
