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Optogentics has previously been utilized to recover vision in mice by Van wyk et al in 2015, but its use in humans remained elusive until now. Two simple questions initially spring to mind:
what is optongenetics?
how does it work ?
To answer the first, Optongentics is a method that allows the control of neuronal activity via the use of light. From this we can infer one reason as to why this research has only just been introduced into human patients despite being around for 6 years. It is the issue of specificity. Optogenetics relies on the use of channelrhodopsins- light sensitive ion channels being placed into specific neurons, for example if Retinal bipolar cells are damaged, introduction of channelrhodopsins can restore vision. Researches primarily do this via the inclusion of the channelrhodopsin DNA in a viral vector. This virus will infect many neurons, but the channelrhodopsin will only be expressed in your specific neurons of interest. This is achieved by the use of Cre-Lox recombination.
A construct of the following order is arranged:
LOXP site STOP CODON LOXP site CrimsonR
Sepertly a Cre-recombinase is placed under a promoter of a gene that is selectively expressed in your neurones of interest. this means that only in the neurons of interest will the Cre-recombinase be expressed, allowing cuts at the LOXP sites, removing the STOP codon and selectively expressing CrimsonR.
This use of Viral vectors limited the use of this in humans due to the apparent ethical and health concerns. would there be any unintended side-effects of using viral vectors? how big of a variable will viral evolution be in this treatment?
What did this experiment do? and what can we learn from it?
Here, Sahel et al used an intraocular injection of an adeno-associated viral vector encoding ChrimsonR, a channel rhodopsin activated by wavelengths of light approximately 590 nm long. The patient, who suffered from Retinitis pigmentosa- a neurodegenerative eye disease which causes blindness through the loss of the death of photoreceptors. The patient will wear specially designed goggles, which can detect local changes in light intensity and then projects corresponding light pulses onto the retina in real time. This results in real time optogenetic activation of the retinal ganglion cells allowing the restoration of vision.
The result of this was a partial restoration of vision, meaning the previously blind patient could now perceive locate count and touch different objects. this is the first report of partial functional recovery from a neuro-degenerative disease following optogenetic therapy. this opens the door to treating a host of degenerative diseases via the use of optogenetics, for example Parkinsons disease
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