The 2026 Nobel prize in physiology or medicine has been awarded to three researchers for discoveries relating to a class of light-sensitive proteins and how they can control the activity of individual cells. In particular, expressing these proteins in nerve cells has enabled neuroscientists to study which circuits in the brain are responsible for different behaviours, and to develop treatments for various neurological conditions.
The Nobel committee awarded the prize to Karl Deisseroth at Stanford University, US, Peter Hegemann at Humboldt University of Berlin, Germany, and Georg Nagel at the University of Würzburg, Germany, for ‘their discoveries concerning light-gated ion channels and optogenetics’.
In the early 1990s at the Max Planck Institute for Biochemistry in Martinsried, Germany, Hegemann was studying the algae Chlamydomonas, which swims towards light. By attaching small electrodes to the cell’s surface, he was able to measure the electrical signals in the algae’s eyespot – an organelle that contains the light capturing-molecule retinal. However, to study this process in more detail, Hegmann attempted to isolate the light-active proteins with which the retinal interacts. While initially unsuccessful, he eventually identified two genes associated with the proteins.
Meanwhile, at the Max Planck Institute for Biophysics in Frankfurt, Nagel was investigating similar proteins. In 1995, Nagel had used egg cells from the African clawed frog to produce and study bacteriorhodopsin – a light-driven proton pump.
In the early 2000s, Hegemann and Nagel combined their expertise, inserting the two genes from Chlamydomona into frog eggs. This method produced the light-activated proteins – known as channelrhodopsins – on the cell’s surface. Shining light on these proteins caused a channel to open, letting ions flow into the cell and creating an electrical signal. The pair repeated their experiments with human and hamster kidney cells, finding that they also produced an electrical impulse when exposed to light.
A few years later, Nagel and Deisseroth introduced the same genes into rat nerve cells cultured in a petri dish. Under blue light, the cells produced a signal that spread to other nerve cells. In 2007, Deisseroth’s group took the concept further by activating nerve cells in the brains of live mice. This laid the foundation for the field of optogenetics, in which light is used to activate and study neural circuits.
Following the prize announcement, Abdel El Manira, a neuroscientist at the Karolinska Institute, Sweden and a member of the Nobel committee, said that optogenetics has ‘transformed neuroscience’. He notes that researchers are now able to study the link between nerve signals and complex behaviours, such as anxiety, fear and thirst.
‘The impact of optogenetics extends far beyond understanding the healthy brain,’ he added. Researchers are actively looking to use optogenetics to develop treatments for conditions such as blindness, depression and dementia.
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