February 7, 2011

Researchers Gain Insight Into Age-Related Blindness

Researchers report in the journal Nature that they have found an enzyme known as DICER1 which stops functioning, resulting in age-related macular degeneration (AMD).

AMD affects one in fifty people over 50 years of age and one in five people over 85 years old. The macula is a part of the eye which sits in the center of the retina and is responsible for the fine detail at the center of the field of vision. As the disease progresses that central vision declines, making reading, driving and recognizing people difficult.

While the exact cause is unknown, the risk factors include smoking, high blood pressure and having relatives with the condition.

Researchers noticed the enzyme was less active in the retina of people with the more common "dry form" of the illness. When the researchers turned off the gene, which makes the enzyme in mice, 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.

University of Kentucky professor Jayakrishna Ambati, told the BBC: "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, told the British news agency: "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."

Head of molecular and cellular neuroscience at UCL, professor Mike Cheetham, told BBC News reporter James Gallagher: "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."

"It will not change a thing for patients immediately but it may lead to new treatments in the long term," says Cathy Yelf, spokesperson for the Macular Disease Society. "This is a very interesting piece of research and provides us with another valuable piece of the AMD jigsaw," she concluded.


Image 2: Geographic atrophy is induced by DICER1 reduction as seen in the retinal photograph (top right, blue arrowheads). This is prevented by blocking Alu RNA (top left). Flat mount pictures show that the degeneration of the RPE cells induced by DICER1 reduction (bottom right) is prevented by blocking Alu RNA (bottom left). Credit: Ambati Laboratory/University of Kentucky


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