Optogenetics, Make Way for Sonogenetics.

     Optogenetics has been a widely used method for triggering excitation or inhibition of specific neurons with stimulation from light (Fenno, Yizhar, and Deisseroth, 390). It has proven its use through extensive research done on a variety of different organisms, mice and rats being some of the most representative. For example, in Dr. Stephen Steidl's presentation, he elaborated on the research he conducted on the dopamine system in rats such as how in the midbrain dopamine systems, many brain areas like the PPTg and LDTg nuclei can be the sources of multiple inputs. To study the effects of PPTg and LDTg, Dr. Steidl utilizied the optogenetic technique in rats and by being able to specify the areas in which he wanted to see the effects of, he gained much more insight into the complex workings of the dopamine systems.  

     This technique has many additional human applications such as studying the therapeutic possibilities available for "depression, Parkinson's disease, and substance abuse" (Fenno, Yizhar, and Deisseroth, 399). However, while this technique has allowed researchers to manipulate neurons in various ways to study potential effects and/or behaviors, it is undeniable that there are some drawbacks to the technique. One of which comes from the necessity of the light stimulus to be extremely close to the target neuron necessitating the insertion of a fiber optic cable into the brain directly.  

     But fear not, there is a potential option where there will be no more holes in the brain or unnecessary damage in the brain of any kind. Sonogenetics is the option for the future and neuroscientist Sreekanth Chalasani has started to build its foundation through his research on C. elegans.

     Sonogenetics is a technique that uses ultrasound to affect behaviors by triggering different neurons. So in essence, it is a variation from optogenetics, where instead of light, ultrasound is used. To develop this technique, Chalasani and his research team proceeded as follows: first, they made genetic modifications in C. elegans so that some of the motor neurons would include TRP-4 ion channels in their cell walls, second, the worms were surrounded in a "fluid containing microscopic bubbles", third, the worms were exposed to ultrasound, which would have an amplified effect due to the microscopic bubbles, and fourth, the ultrasound would affect the TRP-4 ion channels on the specified neurons and consequently, the worms would exhibit a change in behavior (Sample). While it may seem like the specificity that the optogenetic method can achieve is not as clearly evident in the sonogenetic method, this specificity is actually established in the very first step of genetic modification. The ultrasound will only work to stimulate the specific neurons with the TRP-4 ion channels. Furthermore, to extend this technique and try to target neurons in humans, "gene therapy" or even a "therapeutic virus" could be used (Sample). Chalasani has high hopes for this new technique because unlike optogenetics, sonogenetics uses ultrasound, so the ultrasound can just go through the skin (Wagner). 

     While there is a still some time before this technique can be conducted on humans or even on mice, Chalasani hopes that this technique could take the place of "deep-brain stimulation", a treatment used for reducing the symptoms of Parkinson's disease (Sample). Moreover, there is speculation that sonogenetics may even expand beyond neurons but work in areas of our muscles and heart as well. Thus, while sonogenetics is only in the beginnings of its making, the potential that it can bring to neuroscience research as well as therapeutic applications to humans is incredible.

 

Works Cited

 

Fenno, Lief, Ofer Yizhar, and Karl Deisseroth. "The Development and Application of Optogenetics." Annu. Rev. Neurosci. Annual Review of Neuroscience 34.1 (2011): 389-412. Neuroscience Seminar Box Site. Web. 15 Oct. 2015.

Image:

Ibsen, Stuart, Ada Tong, Carolyn Schutt, Sadik Esener, and Sreekanth H. Chalasani. Figure 1: Amplifying Ultrasound Signals Using Microbubbles Modifies Animal Behaviour. Digital image. Nature Communications. Nature Publishing Group, 15 Sept. 2015. Web. 15 Oct. 2015. http://www.nature.com/ncomms/2015/150915/ncomms9264/fig_tab/ncomms9264_F1.html.

Articles pertaining to subject of interest:

Sample, Ian. "'Sonogenetics' All Brain Cells to Be Controlled by Sound Waves." Theguardian. Guardian News, 15 Sept. 2015. Web. 15 Oct. 2015. http://www.theguardian.com/science/2015/sep/15/sonogenetics-allows-brain-cells-to-be-controlled-by-sound-waves.

Wagner, David. "Sound Waves Give San Diego Neuroscientists Control Over Brain Cells." KPBS Public Media. KPBS Public Broadcasting, 28 Sept. 2015. Web. 15 Oct. 2015. <http://www.kpbs.org/news/2015/sep/28/sound-waves-give-san-diego-neuroscientists-control/>.