In The Field

SfN 2009: Optogenetics – the second wave

There are heaps of posters and presentations this year about optogenetics — the technique developed just a few years ago at Stanford by Karl Deisseroth and Ed Boyden, in which neurons can be engineered to respond to light. There’s even a section of the press book on optogenetics. If this had been a year ago, I might have rolled my eyes and thought, “optogenetics is so 2005”, but it looks like the technology is riding on its second wave: it’s out there, people trust it, and now labs are using it in quite creative ways and actually discovering new things about the brain. A few people at the conference are already murmuring about a Nobel for optogenetics.

The hottest thing I saw so far was a poster by Matteo Rizzi and Kate Powell from Michael Häusser’s lab at University College London. The group put the light-sensitive protein channelrhodopsin (ChR2, the most commonly used protein for optogenetics that’s sensitive to blue light) under the control of the promoter for c-fos, a gene that is expressed by recently activated neurons. This way, they could specifically hit neurons that had been involved in a behavior or task. It’s a great new tool that they used to generate a very exciting result, which you can read about on Nature News.

Posters all over the place were using optogenetics’ fast, cell-type specific control to learn more about various circuits, and of course Boyden, now at the MIT Media Lab, and Deisseroth had many posters and gave a number of talks (I only had time for a few posters — there were more than 3,000 posters today alone). A couple of Boyden’s posters were working out how to do simultaneous optogenetic simulation and electrophysiological recordings — many people thought this couldn’t be done, as the light source would cause too much noise. Turns out all you need to do is shield the light source or shield the electrode.

Deisseroth is also doing a lot of work on other light-sensitive proteins, which would respond to a color other than ChR2’s blue. These include NpHR, which is sensitive to yellow; VChR1, which is sensitive to yellow but has the opposite effect of NpHR; OptoXR, which activates second messenger signaling; and a newcomer called GtR3, which is inhibited by blue light. Given the progress already made with ChR2, it’s very exciting to imagine the ingenious ways people will use these various proteins to further dissect neural circuits.


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