Sunday, 20 May 2012

A genetic cure for Myopia?

Myopia (or Near/short sightedness) is an extremely common eye disorder which poses a significant public health problem as researchers believe it is present in roughly half of the world’s population and is in many cases goes un-diagnosed. When you look at an object light enters the eye through the cornea and the lens and is focused onto a small area of the retina which allows you to see that object clearly. Myopia is a refractive error where the eyeball is slightly longer than normal which prevents the light from focusing directly onto the retina but rather slightly in front of it which causes the eye to have trouble focusing on distant objects, which instead appear fuzzy and blurry. Objects that are in close proximity to the eye however still appear clear and unaffected as the light doesn’t travel a significant enough distance to be refracted away from the retina.
For hundreds of years scientists have been trying to identify the cause of short, and with the developments in biology and in particular genetics during the 20th century it became clear that the this was a disease caused by a defect in the human genome. However intensive research during the past 20 years researchers have not been able to understand what caused myopia at the molecular level and have been unable to identify the exact gene responsible. In 2011 however a team of researchers from the Ben-Gurion  University of the  Negev led by Professor Ohad Birk discovered that a mutation in the gene LEPREL 1 was the cause of myopia. They focused on a Bedouin tribe in Israel that had a strong history of myopia and intensively analysed the genome of the population in an attempt to locate the gene/genes responsible for the mutation.
The study found that a gene called LEPREL 1 encodes an enzyme that is essential in the modification of collagen in the eye. Collagen is a group of proteins that is found throughout the body especially in the flesh and connective tissue of mammals. Wherever collagen is present a specific enzyme ‘modifies’ it to serve the specific purpose required by it in that part of the body. When the mutated form of LEPREL 1 is present in a genome the enzyme is coded incorrectly which in turn causes the collagen to be incorrectly ‘modified’. This causes the eyeball to be longer that normal which affects the refraction of light onto the retina leading to myopia.
Although this study has led to an exciting discovery as to the cause of myopia it focused on an extremely small focus group and the researchers behind the discovery themselves admitted that a more in depth study needs to be conducted to determine if LEPREL 1 is the cause of myopia throughout the entire human genome. If this is the case then it will have a significant impact on the lives of many people and may allow a cure for myopia to be developed which would fix the mutation in LEPREL 1.
Reference List:
Mordechai, S, Gradstein, L, Pasanen, A, Ofir, R, El Amour, K, Levy, J, Velfair, N, Lifshitz, T, Joshua, S, Narkis, G, Elbedour, K, Johanna, M, Birk, O 2011, ‘High Myopia Cause by a Mutation in LEPREL 1 , Encoding Prolyl-3-Hydroxylase 2’, The American Journal of Human Genetics vol. 80, pp. 438-445.
Researchers Identify Gene That Leads To Myopia (Nearsightedness) 2011, viewed 18 March 2012, <>
Reece, J, Meyers, N, Urry, L, Cain, M, Wasserman, S, Minorsky, P, Jackson, R, Cooke, B, Campbell Biology, 9th edition, Pearson, China.               

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