Keratoconus causes
distortion of the cornea and can lead to blindness. Thin corneas are an
indication of a risk of developing the disease.
Identification
of specific genetic variants associated with common eye disorders could improve
treatment and prevention
The eye is covered by a clear and protective layer
called the cornea, and abnormal thickness of the cornea can result in eye
disease. An international research team including Chiea Chuen Khor of the
A*STAR Genome Institute of Singapore has pinned down 27 genetic variations that
are strongly associated with a heritable trait known as central corneal
thickness (CCT)1. Some of these variations are also directly linked to eye
diseases, so the findings may lead to better prevention and treatment.
Extreme thinning of the cornea is associated with rare
eye disorders, whereas milder thinning is linked to more common problems. These
include primary open angle glaucoma (POAG), which is the second leading cause
of blindness worldwide, and a progressive eye disease called keratoconus, which
affects 1 in 2,000 people and causes distortion of the cornea and visual
impairment (see image).
In several previous studies, researchers investigated
the genetic basis for CCT by comparing the corneal thickness of individuals
with their genetic fingerprints. This revealed 11 genetic variations linked to
CCT, but with varying levels of certainty; the new study solidified these
findings and uncovered further associated genetic variations.
Khor and co-workers achieved this by collecting and
re-analyzing the data from 13 previous studies as a whole. They identified a
total of 27 genetic variations that are strongly linked to CCT; 16 of these had
previously eluded detection. Furthermore, the researchers found that six of
these variations indicated a risk of developing keratoconus, with one of the
six also linked to POAG.
The new study identified a higher number of genetic
variations associated with eye disease than previous ones because it included
data from over 20,000 individuals. “[Our study] is three to four times the size
of previous studies, and it combines data from Asians and Europeans for the
first time,” explains Khor. “As such, the results are correspondingly rich in
detail.”
The team’s findings not only provide greater insight
into the genetic basis for corneal thinning, but also demonstrate that
associated genetic variations increase the risk of common eye diseases.
According to Khor, this could open up new avenues for dealing with these
diseases.
“We now know the biological targets that are relevant
for disease to occur, and some of these gene targets may be amenable to drug
modifications,” he says. “For prevention, individuals [who carry] multiple risk
variants, and who are deemed to be at very high risk of disease, can be
screened earlier to intervene before blindness occurs.”
The A*STAR-affiliated researchers contributing to this
research are from the Genome
Institute of Singapore
References
- Lu, Y., Vitart, V., Burdon, K. P., Khor, C. C., Bykhovskaya,
Y. et al. Genome-wide association analyses identify
multiple loci associated with central corneal thickness and
keratoconus. Nature Genetics 45, 155–163
(2013). | article
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