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Gene associated with age-related blindness

1 September 2008
Appeared in BioNews 473

Scientists working in China and the USA have identified a gene associated with dry Age-related Macular Degeneration (AMD). AMD is the most common form of visual impairment in the developed world. The research is the first time a gene has been linked with the disease, and will improve understanding and hopefully lead to new treatments. The work was published in the New England Journal of Medicine last week.

'This represents a major step forward in our understanding of the dry form of macular degeneration,' Dr. Kang Zhang, from the University of California, San Diego, co-author of the paper, told the Washington Post.

In AMD, cells of the macular break down, affecting central vision. The macular is a small area in the retina, the light sensitive part of the eye, which processes sharp and clear central vision. AMD occurs in two forms, 'wet' and 'dry'. Currently there is no cure or treatment of dry AMD.

The researchers have found that a gene, named TLR3, is involved with the disease. The gene encodes a protein that has functions in the immune system. They also discovered that a certain allele, or version, of this gene has a protective effect - meaning a person with the allele is less likely to develop dry AMD.

The study has also highlighted an important issue in the treatment of wet AMD. The researchers speculate that experimental treatments for wet AMD, which use so called RNAi (ribonucleic acid interference) to switch off certain genes, may not be suitable for people with the protective TLR3 allele because they could inadvertently switch off the protective version of the TLR3 allele increasing the risk of developing dry AMD.

Dr Zhand told the Washington Post, This [research] raises particular concerns regarding RNAi therapy for wet AMD. But by establishing this link between the treatment for the wet form of AMD and the potential harmful effect on the dry form of the disease, we can perhaps better understand the mechanisms of both diseases.

AMD has also been in the news this week for other reasons: the National Institute for Health and Clinical Excellence (NICE) has announced that the drug Leucentis, which does not use RNAi, will now be available on the NHS to treat wet AMD.

SOURCES & REFERENCES
Gene Linked to 'Dry' Macular Degeneration
The Washington Post |  27 August 2008
Gene Thwarts Dry Macular Degeneration
WebMD |  27 August 2008
Patients to get sight-saving drug
BBC News Online |  27 August 2008
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