Monday, 19 March 2012

Optogenetics is Guiding Cell Function Discovery
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Optogenetics is a technique used to investigate the individual function of specialist cells within the brain. These cells are genetically modified so that they perform an action potential when exposed to specific wavelengths of light. Due to the cell-specific activation, researchers are able to track the progress of the action potential within the body and understand the role of the activated cells. Having this knowledge means that the normal function of different neuron cell types can be discovered as currently these cells are poorly understood (Buchen 2010; Deisseroth 2010). After normal activity of these cells has been determined, investigation into abnormal functioning can begin. Neurological diseases such as schizophrenia, depression and Parkinson’s disease are all thought to have potential cures with the use of optogenetics (Optogenetics and mouse 2010).
In 1971 bacteriorhodopsin was discovered by microbiologists to be sensitive to light. When exposed to light, the microbial releases ions into the plasma membranes between cells. This effectively sets off an action potential within the neurons. A number of such microbials, also referred to as ‘opsins’, are used for optogenetics. Some activate cell firing whilst others inhibit the cell (refer to figure 1). Halorhodopsin, channelrshodopsin and bacteriorhodopsin are all used for optogenetics as they can activate or inhibit neurons when exposed to specific frequencies of light without causing any damage (Deisseroth 2010).

Figure 2. Steps involved in using
optogenetics (Buchen 2010)
Optogenetics involves six steps (refer to figure 2). Firstly, any of the opsins genes discussed earlier are used in conjunction with a promoter and inserted within a virus. A promoter is a genetic aid which enables the opsin gene to be expressed in different animal neurons. The virus is injected into the brain of the animal and transfers the opsin gene and promoter into the neurons. Here the promoter comes into play as its presence ensures that only the specific cell types under investigation are able to express the opsin gene. Via an optic fibre cable, a specific frequency of light is emitted within the brain. Opsin proteins, that have positioned themselves in the membranes of the neuron cells under investigation, trigger the cell when shone with the required wavelength of light (Buchen 2010). The product of these six steps can be seen in the following clip where a mouse is forced to complete anticlockwise circles when specific neurons are activated: http://www.youtube.com/watch?v=obJjXRyDcYE (Optogenetics and mouse 2010).

What makes the use of optogenetics favourable are three main properties: it’s fast, it’s cell-specific and it’s all in a single component unit. One of the greatest problems in the past with trying to activate certain neuron cells was that surrounding cells would also be activated. Optogenetics provides great precision when looking at the function of one type of cell with the use of promoters. The single component opsin genes used allow cell activation to occur at lightening speeds as is normally the case in neurons. The final advantage of using optogenetics is the variety of opsins which can be used to produce different effects including not only excitation and inhibition but also action potential frequency and stimulation varying with light intensity (Deisseroth 2010). It is through the use of optogenetics that the variety of neuron cell types in the brain can be investigated and their role defined with the body. This will ultimately lead to advances in curing neurological diseases.

References:
Buchen, L 2010,‘Neuroscience: Illuminating the brain’, Online journal article from Nature, vol. 465, pp. 26-28, viewed 17 March 2012,< http://www.nature.com/news/2010/100505/full/465026a.html>.


Deisseroth, K 2010, Optogenetics, Nature Methods, viewed 16 March 2012, http://www.nature.com/nmeth/journal/v8/n1/full/nmeth.f.324.html.

Optogenetics and mouse 2010, youtube clip, viewed 17 March 2012,
< http://www.youtube.com/watch?v=obJjXRyDcYE>.

5 comments:

  1. Freakkkkay video! fascinating blog :D

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    1. I'm glad you found it so "fascinating". We're looking for human specimens, would you be interested? Doing circles is a great way to burn carbs.

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    2. Ah yes... thats the onnnnly way to burn carbs :P

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  2. as well as groupstep <(^^<) <(^^)> (>^^)>

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    1. Nuts! Caption:

      "Step, jump over, HEEL TAP! and again"

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