This year's Nobel Prize in Physiology or Medicine has been awarded for the development of optogenetics, a technique that allows researchers to turn specific neurons on and off using light. Originally a laboratory tool, this technology is now expanding possibilities for treating blindness and brain disorders.
Optogenetics involves inserting light-sensitive proteins from microorganisms into specific neurons and then using light to control the activity of those cells. The technique began with the discovery of the protein 'channelrhodopsin' in green algae. Unlike traditional electrical stimulation, which affects surrounding cells, optogenetics selectively regulates only the targeted cells.
Professor Kim Ki-hyun of Seoul St. Mary's Hospital explained, "We can now directly verify the causal relationship between neural circuits and functions by observing which behaviors emerge when specific neurons are activated and how behaviors change when their activity is suppressed. This has significantly changed the way we study complex brain functions such as memory, emotion, reward, and movement."
The applications of this technology extend to disease research as well. Professor Kim Jun-ki of Asan Medical Center noted, "Optogenetics is being used to study the mechanisms behind neurological disorders such as Parkinson's disease, epilepsy, and sleep disorders, as well as to validate new therapeutic targets and drug candidates. It also helps test hypotheses about the effects of developing drugs on the brain." Identifying which cells cause symptoms allows for the design of targeted drugs or therapies.
Initially, the proteins only responded to blue light, which is difficult to penetrate deep into tissues. However, recent advancements have led to the development of proteins that respond to red light and have increased sensitivity, propelling therapeutic research forward. The field that has made the most progress in patient treatment is ophthalmology. Since light can easily reach the eye, introducing light-sensitive proteins into remaining retinal neurons can recreate visual signals even after photoreceptor cells have died.
Professor Kim stated, "Research is underway to provide light-sensing capabilities to the remaining retinal neurons in patients with retinitis pigmentosa, and reports have emerged that some visual functions have been restored." The optogenetic gene therapy 'Mogenly' from the U.S. company Nanoscope Therapeutics has been submitted for FDA approval, with a review target set for the first half of next year. However, applications for brain disorders are still in preclinical stages, with challenges remaining in delivering light deep into the brain and ensuring long-term safety.
The scope of regulation is also expanding beyond neurons. Professor Hyung Soo-jin's research team at Samsung Medical Center summarized studies in a 2023 review published in the journal 'Frontiers in Cellular Neuroscience' that stimulated glial cells, which were previously considered supportive cells for neurons, with light. According to the summarized studies, light-stimulated astrocytes released signaling molecules that altered communication between neurons, while Schwann cells in peripheral nerves produced myelin, the protective sheath around nerves, solely through light stimulation. This suggests that treatment targets could expand to diseases like multiple sclerosis or nerve damage.
Professor Hyung remarked, "The ability to turn neurons on and off with light has become a standard method for elucidating brain function. It is encouraging that we are beginning to provide clues for functional recovery in patients with conditions like terminal blindness, for which there were previously no effective treatments." He added, "While expanding this to other organs remains a challenge, I expect this award will accelerate progress in that direction."
Professor Kim Ki-hyun anticipates that future research will lead to a more precise understanding of the neural circuits related to diseases, paving the way for the development of clinically applicable therapies.
Meanwhile, Karl Deisseroth, a co-recipient of this year's Nobel Prize and a professor at Stanford University, emphasized that optogenetics could offer hope for patients with autism and depression. In an interview with foreign media shortly after the announcement on October 5, he stated, "As a physician-scientist and psychiatrist, I think of my patients suffering from autism and depression. The hope that this research brings is significant."
* This article has been translated by AI.
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