The 2026 Nobel Prize in Physiology or Medicine connects a chain of experiments carried out in Germany and California. Peter Hegemann’s work on how a single-celled green alga senses light led to channelrhodopsins. Georg Nagel and colleagues in Frankfurt showed that these proteins could act as light-gated ion channels. Karl Deisseroth’s Stanford group then put channelrhodopsin into neurons and used flashes of light to control their activity. This Tracespot follows those three places to show how basic research on an alga became one of neuroscience’s most widely used tools.
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1990s–early 2000s
University of Regensburg, Regensburg, Germany
At the University of Regensburg, Peter Hegemann’s group studied phototaxis in Chlamydomonas reinhardtii, a single-celled green alga that can swim toward or away from light. The work focused on the light-sensitive proteins behind that behaviour. After algal gene sequences became available around 2000, the group identified candidate rhodopsin genes. The question was no longer only how the alga behaved, but what the proteins themselves could do.
48.9992°N · 12.0932°E
2002–2003
Max Planck Institute of Biophysics, Frankfurt am Main, Germany
Hegemann asked Georg Nagel at the Max Planck Institute of Biophysics to test the proteins encoded by the algal genes. Working with Ernst Bamberg and colleagues in Frankfurt, Nagel helped show that channelrhodopsins directly form ion channels that open when illuminated. That result made the proteins unusually useful: light could now be converted directly into an electrical change across a cell membrane. The Max Planck Institute describes the Frankfurt experiments as a key step on the path to optogenetics.
50.1737°N · 8.6303°E
2004–2005
Stanford University, Stanford, California, United States
Karl Deisseroth started his Stanford laboratory in 2004 and began testing whether channelrhodopsin could work inside mammalian neurons. His group engineered the protein into selected nerve cells and showed that pulses of blue light could make those neurons fire. The key result was published in 2005. It connected the German work on microbial light-sensitive proteins with a practical method for controlling neural circuits. Optogenetics then developed into a broad toolkit used to study how specific cells contribute to behaviour and disease.
37.4313°N · 122.1744°W