CHLAMYDOMONAS REINHARDTII is not an obvious subject for high-profile research. It is a pear-shaped, single-celled alga which swims around ponds propelled by two flagella. As a photosynthetic organism, which subsists by converting visible light into chemical energy, it often uses those thin appendages to swim towards sources of light. When doing so it is guided by a reddish patch made of protein known as an eyespot. And, in an example of the potential value of even the most off-the-wall scientific research, studying exactly how this eyespot works has led to both a new scientific field, called optogenetics, and this year’s Nobel prize for physiology or medicine.
This insight was confirmed when Dr Hegemann enlisted the assistance of a colleague, Georg Nagel, then at the Max Planck biophysics campus in Frankfurt. Optogenetics permits neuroscientists to use light to instantaneously activate individual brain cells. It has thus transformed neuroscience by making it possible to work out exactly what particular cells are doing. That enables researchers to investigate both basic neurobiology and the neural basis of illness. Testing his guess with the tools then available proved hard, until the blossoming science of genomics came to his rescue. A team of Japanese researchers had produced a map of the DNA of Chlamydomonas, showing that it included two genes resembling those for light-sensitive proteins in some other organisms. Dr Nagel, who shared the prize, inserted the DNA of the two newly identified genes into some frogs’ eggs, which then turned out the desired proteins in quantities large enough to test. Just as Dr Hegemann had predicted, they turned out to be light-stimulated ion channels.
Dr Miesenböck, as an audience member at Monday’s announcement observed, might have serious reason to be miffed. Regardless of details of priority, though, the subject has since exploded. Dr Deisseroth’s lab led the way, first by repeating what had been done in cultured rat cells in living mouse brains, and then by inventing the trick of using extremely thin optical fibres to illuminate, and thus stimulate, groups of neurons. In combination, these tricks let the researchers control the movements of a mouse’s whiskers.
The paper announcing this finding was published in 2005, but other researchers were also exploring similar ideas.
Three years earlier, Gero Miesenböck, then at the Memorial Sloan-Kettering Cancer Centre in New York, had done similar work using a light-sensitive protein from a fruit fly.
