Optogenetics: Lighting up the secrets of the human brain
Discover all you need to know about this innovative method and what it has in store for the future of science and medicine.
Since the beginning of humanity, doctors and scientists alike have struggled to grasp the mysteries of the human brain. As the most complex structure in the known universe, the human brain consists of 100 billion neurons on average. Neurons use electrical impulses and chemical signals to transmit thoughts, behaviours and other information to the rest of the nervous system.
In 1979, Francis Crick, one of Britain’s greatest scientists, published in an article that he believed the greatest challenge facing neuroscientists was the need to control one type of brain cell, without affecting the others. He later proposed that light may be able to solve this issue.
And that’s where optogenetics comes into play.
Simply put, optogenetics is a technique that provides neuroscientists with the ability to control individually selected neurons of the brain. This method combines light and genetic engineering (altering the genetic code of a living structure) to individually control neurons of the brain.
The ideal way to study the property of different types of neurons is to control individual types of cells independently and see what happens when you alter one type of cell. Optogenetics helps to realize this goal.
— Feng Zhang
Pretty cool, right?
The Foundation of Optogenetics
I know what you’re thinking. How does this technique work — what is the science behind it?
Let’s start from the beginning.
Chlamydomonas reinhardtii is a unicellular green alga that uses photosynthesis to create the energy it needs to survive. This organism contains a small organelle called an eyespot. Inside the eyespot are light-sensitive proteins called opsins. Algae use opsins to position themselves in a better position to absorb light to transfer into energy.
Okay . . . so, what does this have to do with optogenetics? Well, optogenetics uses light to control neuron activity
Let’s take a look at optogenetics inside a mouse. To get the opsin into the neurons of a mouse, neuroscientists insert the genetic code for opsin into the genetic code for the neurons of the mouse.
Similarly, if we can successfully insert the genetic code into the human brain, it allows us to control the neurons we chose. Electrical stimulation, on the other hand, is general. It does not allow us to select and target specific neurons or locations.
The most common opsin in neuroscience is channelrhodopsin-2 (ChR2). It is from green algae and responds precisely and only to blue light. Thus, when ChR2 is added to neurons, they can be activated with blue light and will only stay active as long as the blue light is shining on them, entitling us to exact control over timing. Natural neurons are not affected by blue light, so only neurons with ChR2 will be targeted by the blue light.
Optogenetics will help researchers to understand how different neurons control different behaviours. It will allow them the possibility to map the human brain. For example, they will be able to see exactly how areas of the brain collaborate, which areas of the brain are connected, how neurons work together, how information travels in the brain, what happens when there is a disruption in communication between neurons, what happens when a specific area of the brain is damaged and etcetera.
The list is virtually endless.
Ultimately, optogenetics creates undeniable opportunities for neuroscientists to explore how the brain works. It will bring us so much closer to understanding the mysteries of the brain and unlocking its secrets!
Recent Advancements
Optogenetics was initially used by neuroscientists in 2005. Therefore, optogenetic techniques have been used to investigate the brain from a variety of perspectives, ranging from how neurons communicate to the interactions of vast brain regions.
It has also been used to investigate stroke. A stroke occurs when the blood supply to the brain is disrupted or decreased. This prevents brain tissue from receiving the oxygen and nutrients it requires which in turn causes brain cells to die within minutes. Not only does this affect the area of the brain to which the blood supply was disrupted, but also the areas that are connected.
The World Health Organization reports that 15 million people suffer strokes each year, of which 5 million die and another 5 million are permanently disabled.
Optogenetics has been used in mice to explore the changes the brain undergoes following a stroke. In a particular study about the manner in which a small stroke to one area of the brain affected many other areas of the brain, it was concluded that a stroke, no matter the size, can have a significant impact on how the brain functions altogether. Scientists will be able to improve stroke therapies by better understanding what happens to the brain following a stroke.
This is merely one example of how optogenetics can be used to investigate brain-related questions.
Although optogenetics is a comparatively recent method, it has already been approved for its first clinical trials in humans.
A Glimpse Into The Future
We know that optogenetics allows selective control over neurons, but . . . how can that be applied in the future? What potential problems could it solve?
The answer lies partially in mental illnesses including depression, anxiety, schizophrenia, Alzheimer’s, Parkinson’s disease, eating disorders and addictive behaviours that could potentially be resolved.
Each year, mental illness kills 8 million people globally. 8 million. Now, imagine if we could prevent those deaths. How?
You guessed it. Optogenetics.
Ways to treat these illnesses or at least alleviate the symptoms are being explored by scientists. Optogenetics could provide alternatives to the currently prevalent treatment: deep brain stimulation.
What is deep brain stimulation?
DBS is a procedure that involves a neurostimulator, a medical device that sends electrical impulses, through implanted electrodes in the brain, to target specific areas for the treatment of mental illnesses such as Parkinson’s disease and dystonia. Optogenetics offers an alternative treatment. Instead of electrodes, LEDs could be implanted into the brain and used to stimulate solely neurons affected by the disease.
At least 10 percent of the world’s population — approximately 60 million people — suffer from chronic pain. But what if I told you that light could be used to block pain signals. Imagine how many people would be relieved of a huge burden.
Globally, there are an estimated 285 million people who are visually impaired, of whom 39 million are blind. Optogenetics raises the potential of eyesight recovery in blind individuals. Producing photosensitivity in the retinal ganglion cells, which typically obtain sensory input from other specialized cells rather than directly absorbing light, can restore vision to a degree.
Optogenetics could also be used to correct heart rate irregularities. The rate of contractions can be controlled with light impulses using the body’s natural mechanism by inserting sufficient rhodopsins into the sinus node, the heart’s natural pacemaker. Heart rate can be regulated directly if rhodopsins are implanted into cardiomyocytes, the cells that make up the cardiac muscle. Optogenetic pacemakers, which are currently in progress, work on this theory.
There is no doubt that optogenetics could eventually be used to repair failing organs in the human body. And gene therapy will enable us to do this completely noninvasively. If desired, it would even be possible to ‘upgrade’ our bodies by replacing some of their parts with more effective components!
— Vitaly Shevchenko, MIPT Laboratory for Advanced Studies of Membrane Proteins
Wow.
That was mind-blowing. The potential is certainly there.
Optogenetics brings to light many possibilities. Things that we would not have even dared to imagine in the past.
It truly is an innovative science breakthrough that could be used to change countless lives in immeasurable ways.
References
“What Is Optogenetics and How Can We Use It to Discover More ….” 20 Sep. 2017, https://kids.frontiersin.org/article/10.3389/frym.2017.00051. Accessed 20 June. 2021.
“Optogenetics: Shedding light on the brain’s secrets — Scientifica.” https://www.scientifica.uk.com/learning-zone/optogenetics-shedding-light-on-the-brains-secrets. Accessed 20 June. 2021.
“Current and Future Applications of Optogenetics — News Medical.” 23 Aug. 2018, https://www.news-medical.net/life-sciences/Current-and-Future-Applications-of-Optogenetics.aspx. Accessed 20 June. 2021.
“optogenetics | Definition, Method, & Applications | Britannica.” https://www.britannica.com/science/optogenetics. Accessed 20 June. 2021.
“Mortality in Mental Disorders and Global Disease Burden Implications.” https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4461039/. Accessed 20 June. 2021.
“Global data on visual impairment — WHO.” https://www.who.int/blindness/publications/globaldata/en/. Accessed 20 June May. 2021.
