Gene Variations Cause Exfoliation Glaucoma
August 11, 2007
Adapted from deCODE genetics
In a paper published today in the journal Science, scientists from deCODE genetics and academic colleagues from the National University Hospital in Reykjavik and Uppsala University in Sweden report the discovery of two common variations in the sequence of the human genome that appear to account for virtually all cases of a major subtype of glaucoma. The variations are located in the LOXL1 gene on chromosome 15, and confer respectively 26-fold and 8-fold increases in risk of exfoliation glaucoma compared to the low-risk versions of the same markers. Approximately 25% of those in the Icelandic and Swedish study cohorts were found to have two copies of the highest risk variant, putting them at approximately 100 times the likelihood of developing exfoliation glaucoma (XFG) as are individuals with the low risk version of the same variation. The LOXL1 protein encoded by the gene is involved in the formation of elastin fibers which, when they accumulate in the eye, cause XFG.
“This discovery is remarkable and important because the genetics has led us directly to what appears to be the sole cause of a devastating common disease. The risk conferred by these variants is such that it accounts for virtually all cases of exfoliation glaucoma, meaning that if we can neutralize the impact of these variants we might eliminate the disease. The LOXL1 protein made by this gene appears to play a role in the accumulation of fibrous deposits that causes XFG, providing a promising mechanism to target for developing therapy. We plan to conduct additional studies to examine how we can take advantage of this finding to begin drug discovery,” said Kari Stefansson, CEO of deCODE.
Glaucoma is one of the most common causes of blindness worldwide. There are various types of glaucoma, all of which lead to damage in the optic nerve and progressive loss of vision. Exfoliation glaucoma is caused by the buildup of fibrous deposits on the surfaces on the front of the eye. Between 10-20% of people over the age of 60 are believed to have some degree of exfoliation syndrome, and perhaps more than half of these individuals will go on to develop exfoliation glaucoma. The progression of glaucoma can be slowed using various medications that promote the drainage of fluids from the eye and reduce pressure on the optic nerve. However, exfoliation glaucoma is often resistant to drug treatment. Little has been understood to date about the pathophysiology of the disease and there are no treatments targeting the underlying causes of the condition.
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