Optogenetics is one of the most rapidly growing fields of applied research because of its large application potential. It combines knowledge of optics and genetics in order to control and dictate the behavior of cells using light. The ability to control someone else’s body movement might sound like something only possible in movies but as technology progresses and with studies such as optogenetics that might become reality sooner than you think.
So how does this work?
Optogenetic studies focus on regulating the activity of neurons and controlling the signals they send out in order to, not only gain additional and much-needed knowledge on the functioning of the brain, but also to provide potential solutions to certain medical conditions. In order to make the cells responsive to light, scientists have to alter their genetic code to allow for production of photosensitive opsin proteins. They do that by adding special genes found in single cell organisms such as algae into the genetic code for the neurons of the test subject. Most commonly a mouse is used because of how familiar we are with its genetic code. This knowledge also allows us to insert the code into a specific type of neuron or even a specific location in the brain.
The great precision this is done with in living, freely moving animals opens up many possibilities. For example it can be used to control specific behaviors in animals such as triggering or blocking fear or pain responses, as well as to find out more about how individual cells contribute to those behaviors.
Depending of the type of opsin protein used to modify the neuron, it will have either an activating or an inhibiting effect on the nerve impulse (by controlling the movement of charged ions across the cell membrane) in response to light. The most commonly used by scientists is channelrhodopsin-2 or ChR2, an opsin protein which responds specifically to blue light. Currently it is used to activate neurons and astrocysts but could also be used in other cells like cardiomyocytes and skeletal muscle cells.
Real life applications of optogenetics
Optogenetics have predominantly been used in studies conducted on animals, however, their potential in curing or at least lessening the effects of certain medical condition is undeniably great.
It could be used to block pain signals in people with chronic pain who currently rely on pain killers whose effectivity will lessen over time as they develop drug dependence.
By introducing the right opsin protein into the SA node (controls the rate of contractions) or even the cardiomyocytes (cardiac muscle cells) you could regulate the heart muscle contractions and therefore correct heart rate abnormalities. This principle is being used in the development of optogenetic pacemakers, a possible alternative to electric pacemakers.
Optogenetics could also help restore motor functions in patients suffering from paralysis by modifying either motor neurons or the muscle cells themselves so that they are activated by light. In the latter case by illuminating specific muscles you would cause them to contract and therefore cause movement of that body part.
There is also the possibility of eye-sight recovery in blind people when the damage is done to retinal cells. Research on animals have shown that lost vision can be restored to some degree by addition of opsin proteins to retinal ganglion cells which usually receive information from other specialized cells instead of directly absorbing light.
The problem
The biggest problem of optogenetic therapy in humans is that it raises ethical concerns. First there is the problem of irreversible modifications made to the human DNA by adding non-human genes to it. But the other and far more troubling problem is the external control, the idea of a third-party having control of human actions, decisions and at some point in the future possibly even thoughts.
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