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Gene Therapy for Blindness

As published in the journal Nature Medicine on May 24, a 58-year old blind man was able to recover a bit of his vision with the help of gene therapy and specially engineered goggles.


Background


According to an article from Live Science, the patient was diagnosed with retinitis pigmentosa at 18 years old. This condition occurs when the genes an individual carries have mutations that can lead to light-sensitive cells in the retina to break down. According to the National Eye Institute, the disorder may lead to the damage of retinal tissue and, in the case of the patient, complete blindness. In order to restore the patient’s vision, researchers used methods of optogenetic therapy. The man was treated in Brittany, France, and his identity has not been revealed.


What is Optogenetic Therapy?


Optogenetic therapy is a form of gene therapy. As described by Gensight Biologics, the process involves the transfer of a gene that codes for a light-sensitive protein, causing neurons to respond to light. The therapy is currently being researched in applications for conditions such as Parkinsons’ disease, and to see if this method can also help people recover from a stroke. As stated by Science News, this type of gene therapy is different compared to the now traditional gene editing method, which involves the use of CRISPR/Cas9 tools to remove pathogens. These types of therapies are not effective when helping those who have already lost their vision, according to Botond Roska, a neuroscientist and gene therapist at the Institute of Molecular and Clinical Ophthalmology Basel.


Image is courtesy of the BBC.


The Process


The scientists inserted the genes of a protein that is light-sensitive into a modified virus. Then, it was injected into one of the patient’s eyes, specifically into the retina ganglion cells. These neurons are meant to send visual information to the brain. The engineered protein is called ChrimsonR. The protein is originally found in the prokaryotic cell of an algae, which allows for it to detect and move towards sunlight. The researchers planned to make the cells sensitive to yellow light so that the goggles they made would detect light intensity. This would then translate into a signal sent to the patient's retina, eventually activating the ChrimsonR protein.


The Results


An article by BBC News explains how it took several months for proteins to build up in the eye and reach high enough levels for the brain to be able to see again. The first time the patient was able to see was at a crosswalk, and he reported seeing the crosswalk stripes.


“...when he started to report spontaneously he was able to see the white stripes coming across the street, you can imagine he was very excited. We were all excited.”

- Dr José-Alain Sahel, the Institute of Vision


Although his vision isn’t perfect, this innovation is a major improvement and breakthrough in gene therapy and what it can accomplish. According to Roska of the University of Basel, these conclusions prove optogenetic therapy providing partially improved vision is achievable.



Article Author: Idil Gure

Article Editors: Victoria Huang, Sherilyn Wen