Tragedy on the stage is no longer enough for me


A technique called optogenetics has transformed neuroscience during the past 10 years by allowing researchers to turn specific neurons on and off in experimental animals. By flipping these neural switches, it has provided clues about which brain pathways are involved in diseases like depression and obsessive-compulsive disorder. “Optogenetics is not just a flash in the pan,” says neuroscientist Robert Gereau of Washington University in Saint Louis. “It allows us to do experiments that were not doable before. This is a true game changer like few other techniques in science.” […]

The new technology relies on opsins, a type of ion channel consisting of proteins that conduct neurons’ electrical signaling. Neurons contain hundreds of different types of ion channels but opsins open in response to light. Some opsins are found in the human retina but those used in optogenetics are derived from algae and other organisms. The first opsins used in optogenetics, called channel rhodopsins, open to allow positively charged ions to enter the cell when activated by a flash of blue light, which causes the neuron to fire an electrical impulse. Other opsin proteins pass inhibitory, negatively charged ions in response to light, making it possible to silence neurons as well. […]

The main challenge before optogenetic therapies become a reality is getting opsin genes into the adult human neurons to be targeted in a treatment. In rodents researchers have employed two main strategies: transgenics, in which mice are bred to make opsins in specific neurons—an option unsuitable for use in humans. The other method uses a virus to implant a gene into a neuron. Viruses are currently being used for other types of gene therapy in humans, but challenges remain. Viruses must penetrate mature neurons and deliver their gene cargo without spurring an immune reaction. Then the neuron has to express the opsin in the right place, and it has to go on making the protein continuously—ideally forever.

{ Scientific American | Continue reading }