By Adrian Galbreth
The onset of a common and potentially harmful form of eye disease may be predicted by a genetic factor, it has been claimed.
According to experts at the Mayo Clinic and University of Oregon, a genetic factor known as a repeating trinucleotide is a strong predictor of a person's risk of developing the condition Fuchs' dystrophy.
The report, presented at the annual conference of the Association for Research in Vision and Ophthalmology in Orlando, Florida, demonstrates how a variation in the gene for transcription factor 4 (TCF4) was a major cause of Fuchs'.
Fuchs' dystrophy occurs when the cells at the back of the cornea deteriorate, causing fluid build-up that results in swelling and cloudy vision, but until recently the cause of most cases was unknown.
The specialists based the findings on an initial genome-wide association study that revealed a link between Fuchs' dystrophy and the TCF4 gene.
Mayo researchers further defined the association with Fuchs' to be due to unusually long segments of repeated DNA nucleotides in the gene - in this case three nucleotide residues (trinucleotide) repeating more than 40 times, and some as frequently as several thousand times.
Lead researcher Dr Keith Baratz, Mayo Clinic ophthalmologist, explained that the long repeats of trinucleotides "cause havoc", impacting the coding of the TCF4 protein.
He noted that characteristics of trinucleotide repeat diseases include later onset of the condition and progressive degeneration.
In the study, the experts show that a particular repeating trinucleotide, TGC in the TCF4 gene, is a strong predictor of disease.
The specialists assert that while Fuchs' dystrophy has other causes, TCF4 repeat expansion is a "major cause" of the condition in the patients in this study, accounting for about three-quarters of cases.
Further research will now aim to establish whether the same causes apply in wider trials, which could lead to new ways of diagnosing and combating the blinding disease.
by Martin Burns