Peter Hegemann, the biophysicist who tells young scientists to stop improving optogenetics

Peter Hegemann

Born	December 11, 1954 Münster
Occupation	Professor
Awards	Massry Prize · Gottfried Wilhelm Leibniz Prize · The Brain Prize

Ask Peter Hegemann how young researchers could improve optogenetics, and he gives every journalist the same answer: they should not. They should work on something new. It is an odd line from a man the Nobel Assembly has just credited with starting it all, but Hegemann has made a habit of leaving fields before they settle around him. At a press conference at Humboldt University of Berlin he listed the detours: chemist, then biochemist, then a decade of plant physiology, then professorships in biochemistry and biophysics. “And now I am a neuroscientist,” he said, “although I have never done a neuroscience experiment in my life.”

The prize, shared with Georg Nagel of the University of Würzburg and Karl Deisseroth of Stanford University, rewards discoveries concerning light-gated ion channels and optogenetics. The committee’s own account starts with him. “It all began with Peter Hegemann’s curiosity,” its press release says: he wanted to know how Chlamydomonas, a single-celled green alga, manages to swim toward a light source. The answer was channelrhodopsin, a protein that catches light and opens a pore in the cell membrane in a single step. Put into a nerve cell, it lets researchers switch that cell on with blue light. Hegemann still remembers the first comment from the journal Science on the discovery: “An ion channel from pond scum.” The Chlamydomonas community, he adds, was not amused.

Little in his schooling pointed toward any of this. Hegemann was born in Münster on 11 December 1954 and grew up in Aachen in a family of doctors. At a humanist grammar school he spent years translating what he remembers as dull accounts of Roman and Greek wars, and he liked only the sciences, art and music. He played the flute in the school orchestra, rode motorbikes and describes his marks at school and at university as absolutely average. He studied chemistry in Münster and then in Munich, where he moved into biochemistry.

The choice that shaped his career came at the Max Planck Institute of Biochemistry in Martinsried, where he completed his doctorate in 1984 in the group of Dieter Oesterhelt, working on halorhodopsin, a light-driven chloride pump from a salt-loving microbe. Oesterhelt, he recalls, offered him two paths: stay with him as long as he liked, until retirement, or do his own thing and be gone after five years. Hegemann took the second. A paper by Kenneth Foster had proposed that the alga’s light sensor was a rhodopsin, the family of molecules that also works in animal eyes, and Hegemann spent a postdoctoral year in Foster’s laboratory at Syracuse University before returning to Martinsried to lead his own group.

There, in the early 1990s, he found the puzzle that would occupy him for a decade. Using tiny electrodes on the alga’s eyespot, he recorded an electrical impulse half a millisecond after light arrived, more than twenty times faster than the chain of chemical steps that turns light into a signal in the human eye. Hegemann concluded that a single protein had to capture the light and act as the ion channel. Colleagues were sceptical, and the protein fell apart whenever his team tried to isolate it. He moved to the University of Regensburg as professor of biochemistry in 1993. Around the turn of the millennium, in Chlamydomonas gene sequences published by Japanese researchers, his group spotted two candidates and sent them to Nagel at the Max Planck Institute of Biophysics in Frankfurt, who expressed them in frog eggs and watched them open under light. With Nagel and Ernst Bamberg, Hegemann described channelrhodopsin-1 in Science in 2002 and channelrhodopsin-2, the version neuroscience adopted, in PNAS in 2003.

The tool spread quickly. In 2005 Deisseroth’s laboratory used channelrhodopsin-2 to make cultured rat neurons fire on command, and that same year Hegemann co-authored a study in which it switched on neural activity in chick embryos. At Humboldt University, where he became professor of experimental biophysics, his laboratory turned into a workshop for new variants. In 2014 his group turned channelrhodopsin into a light-gated chloride channel that silences neurons instead of firing them. A European Research Council grant awarded in 2016 funded a search for light-sensitive enzymes that turned up the first known heterodimeric rhodopsin. Since 2015 he has held a Hertie senior professorship in neuroscience in Berlin.

The three-name limit on a Nobel Prize simplifies a crowded story, and Hegemann’s own career shows where. Dieter Oesterhelt, the supervisor whose work on microbial rhodopsins underpinned all of this, shared the 2021 Albert Lasker Basic Medical Research Award with Hegemann and Deisseroth, but he died in November 2022, and the Nobel is not awarded posthumously. Bamberg, a co-author of both channelrhodopsin papers, shared the 2013 Brain Prize with this year’s three laureates and is not among them. Even the map is disputed. The committee places the prize-winning discoveries at the Martinsried institute, while the University of Regensburg says the work done in its laboratories laid the foundations. The medical promise is narrow too: the clearest clinical result is one man with retinitis pigmentosa who regained limited sight. Hegemann is also openly critical of how his profession rewards its scientists. In a video in 2023 he urged colleagues to judge young researchers by the originality of their work rather than their publication count after three or four years, which, he said, they unfortunately do not do. He has also told the broadcaster rbb that he often doubted staying in basic research at Humboldt because support fell short.

The news nearly passed him by. He told the Nobel Prize website that on 5 October he ignored an email from a stranger asking him to call back, until he recognised the Swedish dialling code from his sailing trips. At the Humboldt press conference he said that research cannot be done in order to win prizes and praised a group of at least ten nationalities. The university’s leadership has backed optobiology with a new building due for completion in May 2029. He still advises the Regensburg Center for Ultrafast Nanoscopy and is part of a European Research Council Synergy project, running since 2022, that aims to carry optogenetics into a wider range of living systems.

The medal ceremony in Stockholm is on 10 December, the day before his 72nd birthday, and he plans to bring his family and key co-workers. In his Nobel interview he pointed out that the first study of how Chlamydomonas reacts to light was published in 1866 by a Russian scientist who collected his algae from the Neva in St Petersburg and worked without electricity. Hegemann’s advice to whoever comes next is the same one he gives about optogenetics: there are so many interesting creatures to study.

Tags: Nobel Prize, Georg Nagel, Karl Deisseroth, optogenetics, Peter Hegemann, channelrhodopsin, biophysicists