We have heard about different colors in light influencing certain emotions and behaviors but how about taking it a few steps further? Imagine living in a world where a person suffering from a behavioral disorder, for example an obsessive compulsive disorder, can undergo a procedure to be cured. They can go back to living a more functional life and do whatever they love without any obstacles after a clinic visit. A person with a broken bone can speed up the recovery process and get out of the cast within a couple weeks rather than a month. The field of Optogenetics aims to do something about these problems and more. The idea of this field has come into being in 2005 with a paper published by Dr. Karl Deisseroth from Stanford University and Dr. Ed Boyden from MIT in Nature Neuroscience. [ii]
Optogenetics is a genetic technique which uses several tools to control neural activity and specific cell processes with light. [i] The various methods and tools used within this field changes based on the problem at hand. However, the most successful and commonly used protein is Channelrhodopsin (ChR) which is derived from a type of green algae (Chlamydomonas reinhardtii). This protein is able to regulate membrane voltage in response to light. [i] Due to this property it is commonly used in the field of neuroscience to isolate and study specific neural circuits.
A MIT study done on mice exhibiting characteristics of Obsessive Compulsive Disorder (OCD) showed how influential light stimulation can be. The researchers were first able to isolate the neurons by using recordings of neuronal activity. They found that a specific set of neurons were exhibiting communication problems between the neocortex and striatum of the mouse’s brain which could be causing the repetitive behavior of grooming. In this situation, the neural circuit in question was genetically induced to express Opsin, a retinal- binding light-sensitive protein, with the use of a viral concentration. When light stimulation was focused onto this neural circuit the compulsive behaviors greatly diminished. However, when they were not actively receiving the light stimulation, the OCD behavior recurred. [iv] While it is not a complete treatment, Optogenetics has enabled researchers to gain a better understanding of the brain and have a method of targeting a specific circuit without affecting the surrounding cells.
Another use of Optogenetics is the ability to regulate specific ion channels within predetermined cells.[v] In the case of broken bones, research has shown that the light sensitive Ca+2 channels within osteoblasts can be regulated by blue light stimulation. The protein used by researchers to make these specific ion channels light sensitive is called BACCS. This protein is capable of generating Ca2+ signals and can regulate the speed of recovery in both directions if needed. [iii]
Optogenetics is a new field that will continue to improve and provide tools to aid researchers in accurately testing specific hypothesis. Perhaps in the far future scientists will have produced treatments for a range of behavioral disorders, bone deficiencies, and improve regenerative medicine due to these new methods.
[i] Duebel J, Marazova K, Sahel JA. Optogenetics. Curr Opin Ophthalmol. 2015;26(3):226-232. doi:10.1097/ICU.0000000000000140
[ii] Grens, K., 2016. The History of Optogenetics Revised. [online] The Scientist Magazine®. Available at: <https://www.the-scientist.com/the-nutshell/the-history-of-optogenetics-revised-32910>
[iii] Ishii, T., Sato, K., Kakumoto, T. et al. Light generation of intracellular Ca2+ signals by a genetically encoded protein BACCS. Nat Commun 6, 8021 (2015). https://doi.org/10.1038/ncomms9021
[iv] Newsroom | Inserm. 2013. Optogenetics is proving to be highly promising in the treatment of obsessive-compulsive disorders. [online] Available at: <https://presse.inserm.fr/en/optogenetics-is-proving-to-be-highly-promising-in-the-treatment-of-obsessive-compulsive-disorders/8382/>
[v] Spagnuolo G, Genovese F, Fortunato L, Simeone M, Rengo C, Tatullo M. The Impact of Optogenetics on Regenerative Medicine. Applied Sciences. 2020; 10(1):173. https://doi.org/10.3390/app10010173