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Transformative Science: Correcting Vision Loss Through Gene Therapy

Gene therapy is a technique used to replace or supplement a mutated gene with a healthy copy of the gene. Altering these genes has the potential to treat or even cure a wide range of diseases, including vision-related conditions.

Gene therapy is different from traditional drug-based therapy, which may treat symptoms but not the underlying genetic cause. Paul Gamlin, PhD, a professor in the UAB Department of Ophthalmology, is working to apply gene therapy approaches to the eye – in particular, patients diagnosed with retinal degeneration.

For much of his long career, Gamlin has studied how the brain controls eye movements. Specifically, he has researched the retinal ganglion cells (RGCs) that drive pupillary responses. RGCs are a type of neuron located in the retina that indirectly receive visual information from photoreceptors. In 2005, in the course of this research, Gamlin and Dennis Dacey, PhD, a professor in the Department of Biological Structure at the University of Washington, made a novel discovery and identified a new type of cell in the primate retina that controls circadian rhythms and pupillary responses. Subsequent research prompted Gamlin to study how individual retinal cells could be manipulated using gene therapy.

“This discovery led us to become interested in gene therapy approaches to restore vision loss,” Gamlin says. “Over the past few years we have looked at several different approaches at both the RGC and photoreceptor level. For instance, there are some diseases where just a single defect in the DNA sequence produces defects in photoreceptor proteins. Photoreceptors convert light into signals that can stimulate biological processes and relay visual information to the brain via RGCs. When photoreceptors don’t behave appropriately, they stop signaling. When the signaling stops, vision loss or impairment occurs. If we can deliver the correct DNA into these cells, we can restore visual function.”

Introducing healthy genes into the eye requires a delivery vehicle – in this case, a harmless virus. The Adeno-associated virus, or AAV, is not pathogenic, meaning it poses no harm and in some cases can even be beneficial. The virus enters the damaged cell to deliver the corrective gene so that restoration can begin.

“For most retinal degeneration disorders, no effective treatment currently exists to preserve photoreceptors,” Gamlin says. “This could be a preventive approach or more likely a potential treatment for people who are at risk of losing vision or have experienced partial vision loss. The challenge now is to bring this technology to patients with a wide spectrum of blinding eye disorders.”