The genetic factors influencing susceptibility to a degenerative eye disorder are explored in two papers in the September 2006 issue of Nature Genetics. The scientists report that multiple genetic variants together explain a high proportion of inherited individual disease risk.
Age-related macular degeneration - AMD - is a degenerative disorder of the eye affecting the central retina, which gradually reduces vision and is one of the most common causes of vision loss in the elderly. The risk of developing AMD increases with age, and is influenced by environmental as well as genetic components. Previous studies showed that a common, variant form of a protein called complement factor H (CFH) is associated with increased susceptibility to AMD. These new studies show that additional variants within the CFH gene, which do not affect the function of the protein, also make an important contribution to disease risk.
In one study, Gonçalo Abecasis and colleagues examined variants within and surrounding the CFH gene, in AMD patients and healthy individuals from a single study population. They find that variants in the gene encoding CFH, which do not change the protein itself, strongly contribute to the risk of AMD. They also show that multiple variants together define a high proportion of risk.
In an accompanying paper, Mark Daly and colleagues examine an independent set of AMD cases and similarly find that a common non-protein-coding variant in CFH influences disease risk. The authors also confirm previous associations between disease susceptibility and variation in two additional genes, and show that, together, the genetic variation in these three genes defines a broad spectrum of individual disease risk. It has been noted that siblings of individuals with AMD show a 3-6 fold higher incidence of disease compared to the general population. Daly and colleagues estimate that variation in the three genes they study explains roughly half of this increased risk seen among siblings.
Gonçalo Abecasis (University of Michigan, Ann Arbor, MI, USA)
Mark Daly (Massachusetts General Hospital, Boston, MA, USA)
Abstracts available online:
(C) Nature Genetics press release.
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