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Optogenetics () is a biological technique which involves the use of light to control cells in living tissue, typically neurons, that have been genetically modified to express light-sensitive ion channels. It is a neuromodulation method employed in neuroscience that uses a combination of techniques from optics and genetics to control and monitor the activities of individual neurons in living tissue—even within freely-moving animals—and to precisely measure the effects of those manipulations in real-time. The key reagents used in optogenetics are light-sensitive proteins. Spatially-precise neuronal control is achieved using optogenetic actuators like channelrhodopsin, halorhodopsin, and archaerhodopsin, while temporally-precise recordings can be made with the help of optogenetic sensors for calcium (Aequorin, Cameleon, GCaMP), chloride (Clomeleon) or membrane voltage (Mermaid). The earliest approaches for optogenetic control were developed and applied by Boris Zemelman and Gero Miesenböck, at the Sloan-Kettering Cancer Center in New York City, and Dirk Trauner, Richard Kramer and Ehud Isacoff at the University of California, Berkeley; these methods conferred light sensitivity but were never reported to be useful by other laboratories due to the multiple components these approaches required. A distinct single-component approach involving microbial opsin genes introduced in 2005 turned out to be widely applied, as described below. Optogenetics is known for the high spatial and temporal resolution that it provides in altering the activity of specific types of neurons to control a subject's behaviour. In 2010, optogenetics was chosen as the "Method of the Year" across all fields of science and engineering by the interdisciplinary research journal ''Nature Methods''.〔Primer on Optogenetics: Editorial: Commentary: 〕 At the same time, optogenetics was highlighted in the article on “Breakthroughs of the Decade” in the academic research journal ''Science''. These journals also referenced recent public-access general-interest video (Method of the year video ) and textual (SciAm ) summaries of optogenetics. ==History== The "far-fetched" possibility of using light for selectively controlling precise neural activity (action potential) patterns within subtypes of cells in the brain was articulated by Francis Crick in his Kuffler Lectures at the University of California in San Diego in 1999. An early use of light to activate neurons was carried out by Richard Fork who demonstrated laser activation of neurons within intact tissue, although not in a genetically-targeted manner. The earliest genetically targeted method, which used light to control genetically-sensitised neurons, was reported in January 2002 by Boris Zemelman (now at UT Austin) and Gero Miesenböck, who employed Drosophila rhodopsin photoreceptors for controlling neural activity in cultured mammalian neurons.〔 In 2003 Zemelman and Miesenböck developed a second method for light-dependent activation of neurons in which single ionotropic channels TRPV1, TRPM8 and P2X2 were gated by caged ligands in response to light.〔 Beginning in 2004, the Kramer and Isacoff groups developed organic photoswitches or "reversibly caged" compounds in collaboration with the Trauner group that could interact with genetically introduced ion channels. However, these earlier approaches were not applied outside the original laboratories, likely because of technical challenges in delivering the multiple component parts required. In April 2005, Susana Lima and Miesenböck reported the first use of genetically-targeted P2X2 photostimulation to control the behaviour of an animal. They showed that photostimulation of genetically circumscribed groups of neurons, such as those of the dopaminergic system, elicited characteristic behavioural changes in fruit flies. In August 2005, Karl Deisseroth's laboratory in the Bioengineering Department at Stanford including graduate students Ed Boyden and Feng Zhang (both now at MIT) published the first demonstration of a single-component optogenetic system, beginning in cultured mammalian neurons. using channelrhodopsin, a single-component light-activated cation channel from unicellular algae, whose molecular identity and principal properties rendering it useful for optogenetic studies had been first reported in November 2003 by Georg Nagel. The groups of Gottschalk and Nagel were the first to extend the usability of Channelrhodopsin-2 for controlling neuronal activity to the intact animal by showing that motor patterns in the roundworm ''Caenorhabditis elegans'' could be evoked by targeted expression and stimulation of Channelrhodopsin-2 in selected neural circuits (published in December 2005). Now optogenetics has been routinely combined with brain region-and cell type-specific Cre/loxP genetic methods developed for Neuroscience by Joe Z. Tsien back in 1990s 〔Tsien JZ, et al (1996). Subregion- and cell type-restricted gene knockout in mouse brain. Cell. 1996 Dec 27;87(7):1317-26.http://www.sciencedirect.com/science/article/pii/S0092867400818267〕 to activate or inhibit specific brain regions and cell-types in vivo. The primary tools for optogenetic recordings have been genetically encoded calcium indicators (GECIs). The first GECI to be used to image activity in an animal was cameleon, designed by Atsushi Miyawaki, Roger Tsien and coworkers. Cameleon was first used successfully in an animal by Rex Kerr, William Schafer and coworkers to record from neurons and muscle cells of the nematode ''C. elegans''. Cameleon was subsequently used to record neural activity in flies and zebrafish. In mammals, the first GECI to be used in vivo was GCaMP, first developed by Nakai and coworkers. GCaMP has undergone numerous improvements, and GCaMP6 in particular has become widely used throughout neuroscience. In 2010 Karl Deisseroth at Stanford University was awarded the inaugural (HFSP Nakasone Award ) "for his pioneering work on the development of optogenetic methods for studying the function of neuronal networks underlying behavior". In 2012 Gero Miesenböck was awarded the (InBev-Baillet Latour International Health Prize ) for "pioneering optogenetic approaches to manipulate neuronal activity and to control animal behaviour." In 2013 Ernst Bamberg, Ed Boyden, Karl Deisseroth, Peter Hegemann, Gero Miesenböck and Georg Nagel were awarded The Brain Prize for "their invention and refinement of optogenetics."〔(【引用サイトリンク】url=http://www.thebrainprize.org/flx/prize_winners/ )〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Optogenetics」の詳細全文を読む スポンサード リンク
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