Lighting the Way Forward

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Science  16 Jan 2009:
Vol. 323, Issue 5912, pp. 311
DOI: 10.1126/science.323.5912.311a

The controlled expression of foreign genes has enabled all sorts of pyrotechnic displays, from the creation of carotene-rich golden rice to the riotous palette of neuronal arbors revealed via Brainbow by combinatorial derivatives of green fluorescent protein. In most instances, genes from the microbial world are identified, modified, and then packaged for delivery and expression in plant or animal tissues, sometimes for purposes completely unrelated to the specific aims for which the original research was funded. Berndt et al. describe one of the latest such endeavors, in which light-activated channelrhodopsin-2 (ChR2)—a cationconducting protein from green algae—was engineered, on the basis of detailed structure-function analyses of the bacteriorhodopsin photocycle, and converted into a switch. Changing a single cysteine residue yielded a neuronally expressable ChR2 variant that turned on (and stayed on) when illuminated with 470-nm light for 10 ms, and could then be turned off with a 50-ms pulse of 530-nm light. These properties allow for non-invasive modulation of the membrane conductances of individual neurons with innocuous illumination. — GJC

Nat. Neurosci. 10.1038/nn.2247 (2008).

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