Optogenetics Turns 10: A look at the technique that changed how we study the brain, featuring the head of the Media Labs Synthetic Neurobiology group, Ed Boyden. Ten years ago, Karl Deisseroth and Ed Boyden performed a series of late-night experiments that launched a new era in neurobiology research. The pair were collaborating on the idea that they could control neural behavior using only light to activate specific ion channels that could then activate neurons. If such a channel could be made to open on demand, they reasoned, it could be used to probe neural function, connectivity, and even neurological disease. By restricting expression of the light-sensitive channels to certain smell receptor neurons, for example, researchers could induce an animal to smell something that isnt there and then watch what happens. They were actually not the first to have this idea. The concept of using light to control action potentials in neurons was initially proposed years earlier by DNA structure pioneer Francis Crick. The tools needed to implement such an idea were even known to exist—microbial opsins, a class of proteins that includes bacteriorhodopsins, halorhodopsins, and channelrhodopsins, were known to move charged particles across bacterial membranes in response to light—but nobody had been able to put them together into a useful neurobiological tool. Deisseroth and Boyden keyed in on one of those microbial opsins, channelrhodopsin-2 (ChR2), which is a light-gated cation channel. When illuminated with light, ChR2 opens to allow positively charged ions to flow into a cell. Between March and July of 2004, the researchers obtained a clone of ChR2 from Georg Nagel, expressed it in rat neurons, and showed by “activity-dependent transcription factor activation” that the channel seemed to work. In the early hours of August 4, 2004, Boyden placed the cells under a microscope, attached an electrode to one genetically modified cell, and flipped the light switch. Momentarily bathed in a blue glow, the neuron depolarized. biotechniques/BiotechniquesJournal/2014/July/OPTOGENETICS-TURNS-10/biotechniques-352735.html?pageNum=1
Posted on: Sat, 12 Jul 2014 16:03:06 +0000