Tuesday, 3 April 2012

Gene Therapy Combats Inherited Blindness - Joshua Perrin

Gene Therapy Combats Inherited Blindness

Description: File:Protein RPE65 PDB 3FSN.png
Imagine the world without the ability of vision or with impaired vision. Would you be able to cope? For some, this is the reality they are given with no alternative. They are born into this life and up until recently the only option available to those with this fate was to endure and carry out their lives. The first is X-linked, which results only in males receiving an abnormal gene from their carrier mother. The second and third form, dominant and recessive, are similar to one another in that sense that they both require abnormal genes from their parents however, dominant only requires one in total whereas recessive requires one from each parent. [1] An example of inherited vision disease is Leber Congential Amaurosis (LCA). LCA is the result of the RPE65 gene being defective. This gene is responsible for producing enzymes in order to breakdown vitamin A for use by photoreceptor cells in the retina; hence a faulty RPE65 gene drastically affects the production of this enzyme. [2] Now however, a breakthrough in genetics has led to the discovery that gene therapy can be used to treat these patients.

LCA is treatable through a procedure known as gene therapy. The method that is used for this was to have genes with the capability of repairing the tissue of the retina. Simply, normal copies of the RPE65 genes are injected to replace the defective RPE65 genes. When one mentions a virus everyone instinctively imagine these organisms as “the bad guys”.  These RPE65 genes are delivered to the patient via eye surgery in the form of an injection of a genetically engineered disabled adeno-associated virus, commonly referred to as a vector. [3] As there is now a presence of functional RPE65 genes, the enzyme begins to develop which results in an increase in vision efficiency.
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Jean Bennett and Albert Maquire are two of the scientists who explored this area of researched and also used this gene therapy of humans who had not yet fully become blind. Patients who underwent this procedure were monitored afterwards to keep track of progress and to monitor if any side effects occurred. Results proved that within the first two weeks that all the patients who participated in this treatment all showed improvement in their vision. Of the twelve people in the initial trial, six of these patients were no longer considered to be legally blind. [4] One of the post-operations tests was a standard obstacle course which was designed to test the patient’s ability to navigate through the use of vision. The conclusive results showed that the patients had were able to navigate themselves much more confidently indicating an improvement. A second round of this procedure commenced on the same patients. The results of this experiment showed that this extra injection of the gene further improved the vision of the patients. Not only this, it was also concluded that in terms of the input from the retina the responsiveness of the brain was also enhanced. [4]

In conclusion this area of research has high hopes for the future and given the efficiency of the results the patients presented this may very well be the way to go in treating vision disorders among those in the general population. The only downside to this procedure is that it has not been tested on those that are already blind so further research is needed into this field to determine course of action for those who are already blind. With this in mind, this research project has definitely opened doors to a critical area.

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1. (William, 7th October 2010)
2. (Manning, N.D)
3. (Science Daily, 2008)
4. (Jabr, 2012)

Jabr, F (8th February 2012). ‘Sight Seen: Gene Therapy Restores Vision in Both Eyes’ [WWW] Scientific American. Available from: http://www.scientificamerican.com/article.cfm?id=gene-therapy-blindness [accessed: 14th March 2012]


Jabr, F (8th February 2012). ‘Sight Seen: Gene Therapy Restores Vision in Both Eyes’ [WWW] Scientific American. Available from: http://www.scientificamerican.com/article.cfm?id=gene-therapy-blindness [accessed: 14th March 2012]


Manning, A (N.D). The Gene Therapy Journey: From Bench to Bedside’ [WWW] National Eye Institute. Available from: http://www.nei.nih.gov/lca/blindness.asp [accessed: 14th March 2012]


Science Daily (27th April 2008). ‘Gene Therapy Improves Vision In Nearly Blind Patients’ [WWW] Science Daily. Available from http://www.sciencedaily.com/releases/2008/04/080427194726.htm [accessed: 14th March 2012]

William, S ( 7th  October 2010). Hereditary blindness: the parents' dilemma’ [WWW] The Telegraph. Available from: http://www.telegraph.co.uk/health/8046393/Hereditary-blindness-the-parents-dilemma.html [accessed: 14th March 2012]

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