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Researchers Find Gene That Plays Role in Age-Related
Macular Degeneration
 March 11, 2005 – Researchers say their discovery of
a gene associated with age-related macular degeneration (AMD), the
leading cause of blindness in senior citizens 60 and older, opens the
door for more study of the role of genes in AMD and possible treatments.
No cure exists today.
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Macugen Hits Market to Treat Age-Related Macular Degeneration
Jan. 21, 2005 - Macugen (pegaptanib sodium
injection), the recently FDA-approved treatment for neovascular
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Pharmaceuticls, Inc. AMD is the leading cause
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Dec. 30, 2004 – Macugen (pegaptanib), the recently
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citizens. More...
12/30/04*
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AMD is the leading cause of blindness in the
developed world, and most sufferers are older than 60. It causes a loss
of the central visual field necessary for detailed sight, reading,
driving, sports participation and watching TV and movies. A
characteristic of AMD (both the "dry" and wet forms) is the build up of
fatty deposits called drusen in the macula, the central region of the
retina.
By combining the tools of high-throughput biology
and statistical genetics, scientists at Rockefeller University, Yale
University School of Public Health and the National Eye Institute have
identified a gene that confers susceptibility to age-related macular
degeneration (AMD).
Reported in the March 10 issue of Science Express,
the finding opens the door for new investigations of the role of genes
in developing AMD and possible treatments for this disease.
"We have shown that a variant, or polymorphism, of
the complement factor H gene, which alters a protein whose normal
function is to regulate the immune system's attack of foreign invaders
and abnormal cells, is involved in the development of AMD," says senior
co-author Jürg Ott, Ph.D., professor and head of the Laboratory of
Statistical Genetics at Rockefeller. "We believe this polymorphism is a
strong risk factor for the disease."
The gene variant, known as a single nucleotide
polymorphism (SNP), derives from a single letter difference in the
genetic sequence of DNA. Some of these differences may change a gene's
protein products in ways that may confer susceptibility to -- or
protection from -- diseases. In this case, the complement factor H (CFH)
SNP associated with AMD encodes for a different amino acid, as histidine
substitutes for tyrosine at a specific position. The CFH gene lies in a
region of human chromosome 1 that had been linked previously to AMD
through family studies by other researchers.
The research team was led by senior co-author
Josephine Hoh, Ph.D., an assistant professor in the Division of Chronic
Disease Epidemiology at Yale's School of Public Health. Before joining
Yale in 2003, Hoh was a research assistant professor in Ott's lab.
For the research reported in Science Express, Hoh
used DNA taken from blood samples collected for the National Eye
Institute-sponsored Age-Related Eye Disease Study (AREDS). The AREDS was
designed to learn more about the natural history and risk factors of AMD
and cataract and evaluate the effect of high doses of antioxidants and
zinc on the progression of these conditions.
Hoh and colleagues analyzed DNA from 96 unrelated
patients with an advanced form of AMD and 50 healthy people who had
little or no drusen deposits in their retinas.
The controls were chosen to be older than those
with AMD. The study was carefully designed by matching other potential
factors such as ethnicity, gender and smoking to ensure the only
differences between the two study groups was disease status and genetic
background
The researchers genotyped more than 116,000 SNPs
using the most advanced microarray technology and compared the frequency
of each of the 116,000 SNPs in the two groups, patients and controls.
Under the superevision of Hoh and Ott, Ott lab
member Robert Klein, Ph.D., the first author of the paper, played a
major role during course of the project, which include genotyping and
analyzing the data generated by the microarray.
"Robert's unique background of molecular and
computation biology was crucial to the success of this project," says
Hoh.
Biochemical analysis of drusen by other researchers
has shown that the deposits are largely composed of lipids, but a small
portion of the drusen are components of the immune system called
complement. The complement system is a collection of related proteins
that are the body's front-line defense system -- the innate system --
that attacks foreign invaders while usually avoiding any attacks against
healthy cells, the "self." And one of the known properties of factor H
is that it regulates the activation of complement components.
The researchers examined the eyes of four patients
with AMD and found complement debris in the drusen, as well as in eye
components called Bruch's membrane and the intercapillary pillars. Other
researchers also have detected complement components in the drusen of
humans.
"The polymorphism
produces a change in a specific amino acid in the complement factor H
protein, which is located in the region that interacts with C-reactive
protein and heparin," says Hoh. C-reactive protein is associated with
heart disease and high cholesterol levels and both C-reactive protein
and heparin are associated with AMD.
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