Controlling with Light

Researchers from the Massachusetts Institute of Technology have developed a protein that is light sensitive and can enable control of brain activity through optogenetics.

Optogenetics is a laboratory tool for shutting off or stimulating specific types of neurons in the brain, allowing neuroscientists to learn much more about their function.

Optogenetics involves shining a light on the neurons to suppress or stimulate electrical signals within cells. For this the neurons must be genetically engineered to produce light-sensitive proteins known as opsins that are channels or pumps which influences electrical activity by controlling the flow of ions in or out of cells. The light is shone by inserting a light source such as an optical fibre into the brain. However, the invasive procedure is incompatible with many kinds of experiments and its interaction with the brain physiology could be harmful. Therefore, in order to find a better alternative, researchers turned to the natural world. They identified two light-sensitive chloride ion pumps that respond to red light which penetrates deeper into living tissues, unlike natural organisms that use opsins to detect green or blue light. However, it did not induce strong enough photocurrent to be able to control neuron activity. Scientists then engineered one of the relatives of these proteins which resulted in Jaws – the protein which retains the red light while having a much stronger photocurrent.

With this opsin researchers were able to shut down neuronal activity in a mouse brain with a light source outside the rodent’s head. The suppression occurred as deep as 3 millimeters in the brain, and was just as effective as that of existing silencers that rely on other colours of light delivered via conventional invasive illumination. A key advantage to this opsin is that it could enable optogenetic studies of animals with larger brains.