Maggie Demonia
Like the origins of life on Earth, the inspiration behind this year’s Nobel Prize-Winning discovery can be traced back to a single-celled organism. Optogenetics, a method using an algae-derived protein controlled by light to activate nerve signals in the brain, earned Peter Hegemann, Georg Nagel, and Karl Deisseroth the 2026 award in Physiology or Medicine. The technique, which is currently used as a research tool to map neuronal function and networks, also “makes it possible to show how nerve cells shape memories, feelings, and behaviors in the living brain,” according to the Nobel Assembly.
But how can an LED lightbulb and a species found in pond scum change the way we study the brain? The answer lies in a type of protein called microbial rhodopsins. Microbial rhodopsins are a class of proteins found in single-celled organisms such as archaea, bacteria, and some algae. These proteins use light to transport charged ions across the cell membrane and inside the cells. This process changes the charge on either side of the cell membrane, eventually directing the cells to the direction of the light source. Dieter Oesterhelt and Walther Stoeckenius began laying the groundwork for the field in the 1970s with the discovery of bacteriorhodopsin, a protein from the archaea species Halobacterium halobium that functions as a pump to transport ions when activated by light. This finding spurred subsequent research of photosensitivity in numerous other microorganisms.
After three decades of discovery in the field of microbial rhodopsins, Peter Hegemann became interested in the mechanism behind the light sensitivity of the green algae species Chlamydomonas reinhardtii and how they manage to swim towards light. Collaborating with Georg Nagel, the two men identified a new rhodopsin called channelrhodopsin in 2003. What makes channelrhodopsin unique among microbial rhodopsins is the speed at which it works. Functioning as an ion channel rather than a pump like other rhodopsins, channelrhodopsin transports charged ions much faster than other proteins in the same family.
Inspired by Hegemann and Nagal’s discovery, Karl Deisseroth saw the potential use in neuroscience. While photosensitive microbes use the transport of positively charged ions to find a light source, that same depolarization process is how neurons fire signals in the brain. In 2007, Deisseroth published his work in which he introduced the gene that encodes channelrhodopsin into neuronal cells in living mice. Now expressing the channelrhodopsin protein, the neurons in these mice could be depolarized and signal to surrounding cells using light activation via an optical fiber implant. This new tool functions as a light switch, allowing scientists to control specific neurons or neuronal networks in mice and providing invaluable insight into how cell signals in the brain impact health and behavior.
While optogenetics has proven to be a groundbreaking technique for researchers, clinicians hope that the applications will soon expand to treating patients. A better understanding of how the brain functions in the context of neurological and psychological disorders leads to hope for better treatments for patients with conditions such as Alzheimer’s, Parkinson’s, schizophrenia, depression, anxiety, and addiction. The technique may also be used beyond the brain. Clinical trials for vision loss due to retinitis pigmentosa have already partially restored vision for some patients using optogenetics in the retina, with further sights set on the treatment of hearing loss or insulin production in patients with diabetes.
Having only scratched the surface of a technology with such potential, one can only assume that the things we will uncover will be illuminating.
Peer Edited by: Lizzy Taggart
