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Optogenetics may allow us to use light like a remote control for our brains, and treat diseases like retinitis pigmentosa.

Hosted by: Stefan Chin
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Sources:
https://www.newyorker.com/magazine/2015/05/18/lighting-the-brain
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4756725/
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[♪♩INTRO].

Imagine being able to remote control your cat. By clicking a remote at a receiver on your beloved kitty’s head, you could make it walk, turn in circles, or even stop moving altogether.

Maybe, with the press of a button, you could even put it to sleep or turn off its sense of pain when it hurt itself. And even weirder, what if you could control your own body that way? Well, there’s a scientific technique that might someday deliver just that.

It’s called optogenetics, and it’s a method for controlling the function of cells using light. Even though it sounds a lot like mind control, optogenetics is really most useful for learning what specific cells do, or for treating certain conditions. It does this by using light to control certain pathways on a cell’s surface called ion channel receptors.

These are sort of like switches that start and stop electrical signals traveling down your cells. Normally, they’re activated when molecules like neurotransmitters attach themselves to the receptor. That causes charged atoms, or ions, to move into the cell, which generates an electrical current that can make other cells stop or start firing.

These channels are ultimately what makes your body move and function. Optogenetics works by using light to control this process instead of molecules like neurotransmitters. Using fiber optic wires, scientists can transmit precise light pulses that last just one thousandth of a second directly to a small group of cells.

And that triggers ion channels to open and start sending signals. Now, even before this method, researchers had actually been trying to control ion channels for years, since that could help us figure out how cells work or even treat some diseases. But other methods, like drugs or electrodes, tend to be too slow or imprecise.

To really study a small number of neurons, researchers needed fast, accurate signals. And that’s where optogenetics shined a light on the problem… literally. It all works thanks to special proteins called opsins, which are naturally found in organisms like microbes or green algae.

When they’re exposed to certain particles of light, they’ll generate an electrical signal and open a cell’s ion channels. We’ve actually known this about opsins since the 1970s, when researchers noticed that one in certain bacteria, called bacteriorhodopsin, opened its ion channels in response to green light. And today, we know about plenty of others, which start and stop firing neurons in response to all kinds of light.

But no matter how many opsins we found, it took until the beginning of the twenty-first century for scientists to really understand the applications of them. They realized that, if they could somehow get these opsins into animal cells, they’d be able to control the ion channels in the fast, accurate way they needed. And in 2005, they did it for the first time.

In the journal Nature Neuroscience, researchers announced that they’d introduced opsins into a rat’s brain cell — although the cell was in a petri dish and not a live animal. When they shone blue light on it, it showed a spike in electrical activity. Essentially, they had made a light sensitive brain cell!

But trying this on live mammals was a lot harder, because smuggling opsins into a living cell is a tricky business. To do it, researchers had to develop a special virus that could transfer the protein onto the surface of an animal’s cells — without the virus itself running haywire. Then, if that worked, they could just insert a wire into the animal’s brain and use an.

LED or laser to start manipulating neurons. And they did it! In 2007, scientists demonstrated this technique for the first time in a live animal, by applying optogenetics to cells in the motor cortex of a mouse.

By transmitting blue light down the optical fiber in the mouse’ brain, they could make the mouse walk in circles and make it stop when they turned off the light. Pretty weird. Many other studies also use optogenetics to study how cell activity correlates with behavior and bodily function.

For example, in one study from the journal Nature, the researchers manipulated cells that put fruit flies to sleep, then could wake them up on command. Those same cells are involved in the fruit fly’s internal sleep clock, which has similarities to the one in humans. In mice, researchers have also used optogenetics to study behavior related to hunger, which could help us model obesity in people.

It even has a role in helping us understand -- and maybe someday treat -- certain diseases. Like, back in 2011, in the journal Molecular Therapy, researchers claimed they’d used optogenetics to restore light sensitivity to cells in a mouse that had lost its vision. That could someday help develop human treatments for a disease called retinitis pigmentosa, which destroys light sensitive cells in the retina and causes blindness.

And another study, from the journal Neuron, pinned down specific mice neurons involved with motor control. In humans, cells in a similar part of the brain are affected by Parkinson’s disease. Now, even though mice, rats, and fruit flies have brain structures with some features in common with humans, our brains are way more complicated to understand.

We’ll need a lot more work before we’re ready to give everyone remote controls for their brains. Still, it’s possible that, some day, tiny optogenetic devices will be working away in our bodies, offering targeted therapies and cyborg-style nerve implants. We’re definitely there yet.

But if it ever happens, just be careful not to leave the controls to your body lying around the house. If your cat sits on it, it might end up controlling you instead. Although, really, I guess that’s not much different from owning a cat today anyways.

Thanks for watching this episode of SciShow, brought to you by our awesome patrons on Patreon! If you want to help us keep making episodes like this one, you can go to patreon.com/scishow. [♪♩OUTRO].