A new study in the journal Nature has reported the pathology of blindness caused by age-related macular degeneration or AMD. This condition affects more than 50 million worldwide and is incurable. The researchers report that when an enzyme known as DICER1 stops functioning AMD starts to develop.
The macula is a part of the eye that is situated at the center of the retina and is responsible for the fine detail at the centre of the field of vision. With progression of AMD the central vision declines, making reading, driving and recognizing people difficult. It affects 1 in 50 people over age 50 and 1 in 5 people over age 85. The exact cause is unknown, but risk factors include smoking, high blood pressure and having relatives with the condition. This study according to experts could shed light on the condition and is an important breakthrough.
The researchers noted that the enzyme DICER1 was less active in the retina of people with the more common “dry form” of AMD. They then knocked off the gene which makes the enzyme in mice and found that the animal’s retina cells were damaged. It was then discovered that DICER1 is necessary for destroying small pieces of genetic material called Alu RNA. Without DICER1, the Alu RNA accumulates with toxic consequences leading to the death of the retina.
Lead researcher, Professor Jayakrishna Ambati, from the University of Kentucky said, “This work opens many new doors of research… First, we need to identify various classes of molecules that can either increase DICER1 levels or block Alu RNA so that these can be evaluated in clinical trials… Second, we need to understand more about the biological processes that lead to reduction in DICER1 levels and the precise source of the Alu RNA transcripts.”
Professor Ian Grierson, school of clinical sciences at the University of Liverpool, added, “This is a great piece of science which provides another jigsaw piece which we need to put together with other findings…It was done in an animal model which is a long way from the patient, the breakthrough is we’ve got another player.” Professor Mike Cheetham, head of molecular and cellular neuroscience at UCL, also said, “It’s a potentially very important breakthrough which gives insight into this dry form of the disease…It could provide new pathways to therapy, but the findings need to be validated by other researchers.” Cathy Yelf, spokesperson for the Macular Disease Society, said, “This is a very interesting piece of research and provides us with another valuable piece of the AMD jigsaw…It will not change a thing for patients immediately but it may lead to new treatments in the long term.” Dr. Napoleone Ferrara, a researcher at biotechnology company Genentech added, “Ambati’s latest research provides important mechanistic insights in geographic atrophy, and identification of this novel pathway may result in new therapeutic targets for a major cause of blindness.” “The authors have opened an important line of research with real possibilities for future therapeutic intervention for patients with geographic atrophy,” added Dr. Stephen J. Ryan, president of the Doheny Eye Institute
Dr Ambati has created two treatments that could potentially halt the progression of the disease. One works by boosting levels of Dicer, the other breaks down the toxic Alu RNA. The University of Kentucky has applied to patent the techniques and the first trials on people could start by the end of this year.
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