Genetic causes of rare eye disorder discovered
9 September 2011
The study, part-funded by the Wellcome Trust, found that the disorder was associated with mutations in a gene that encodes the antioxidant protein peroxidasin - which makes up part of the lens and cornea in the eye.
The work may help to identify new treatment opportunities for adults and children with this form of inherited blindness and should also make it easier to identify families with the condition who are at increased risk of conceiving a child with severely impaired vision.
The lens and cornea make up the clear 'window' at the front of the eye. But if these structures do not develop correctly then the window can become cloudy, making it difficult to see clearly. If the problems are not treated, they can get worse, leading to glaucoma and eventually blindness.
Led by researchers at the University of Leeds and Flinders University in Adelaide, Australia, the team looked at DNA from three unrelated families with a history of poor vision from birth linked to problems with the eye's lens and cornea.
They discovered that all of the various family members with impaired vision had defects in peroxidasin, and concluded that these defects are responsible for causing cataracts and glaucoma in children with this rare form of inherited eye disorder.
Dr Manir Ali of the University of Leeds explained: "We know that in healthy eyes, peroxidasin acts as a first line of defence against the damage that ultraviolet radiation and sunlight does to our skin. It may also help protect against cataracts in older people. Our findings imply that this same protein is essential for the normal development of the lens and surrounding structures at the front of the eye."
Full details of the study are published in the latest issue of the 'American Journal of Human Genetics'.
The discovery was made using next-generation DNA sequencing, a new way of reading genes quickly and spotting errors that cause inherited diseases. Dr Ali and colleague now plan to use the same approach to screen all the eye's genes at once, so that all patients with inherited blindness can find out exactly what is causing their illness and can receive the appropriate treatment.
"This DNA-sequencing technology looks set to revolutionise the medical world, giving patients and their doctors more information than ever before about their genetic make-up and how it can affect their health and response to treatment," Dr Ali added.
Image: Composite image of the eye. Credit: Shelley James/Wellcome Images
Reference
Khan K et al. Homozygous mutations in peroxidasin (PXDN) cause congenital cataract, corneal opacity and developmental glaucoma. Am J Hum Genet 2011 [epub].
