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Repeating trinucleotide associated with ability to predict Fuchs’ corneal dystrophy
FORT LAUDERDALE, Fla. — A repeating trinucleotide, specifically TGC in the TCF4 gene, is a strong predictor of Fuchs’ corneal dystrophy , a speaker here said.
In a press release, the Mayo Clinic attributed the association with Fuchs’ to “unusually long segments of repeated DNA nucleotides in the gene.” In this case, the trinucleotides repeat more than 40 times and sometimes several thousand times.
“Currently there are only a handful of diseases that are attributable to trinucleotide expansion,” Keith H. Baratz, MD, said at the Association for Research in Vision and Ophthalmology meeting.
The TGC expansion is a better predictor of Fuchs’ corneal dystrophy than the minor associated allele, the SNP rs613872, which has positive predictive value of only 79%, whereas the TGC expansion carried a 96% positive predictive value, Dr. Baratz said.
Many of the associated characteristics of Fuchs’ corneal dystrophy are consistent with those of other diseases associated with trinucleotide repeats, namely, late-onset, progressive degeneration involving primarily non-replicating tissue, and a dominant pattern of inheritance with variable expression, Dr. Baratz said.
“One aspect of trinucleotide disorders that we do not normally associate with Fuchs’ is the phenomenon of anticipation, in which affected individuals tend to have earlier onset and more severe disease,” he said.
Dr. Baratz said that this research establishes an association between the trinucleotide TGC repeats and Fuchs’ corneal dystrophy but does not establish cause and effect.
- Disclosure: Dr. Baratz holds a patent for diagnostic and therapeutic target for endothelial dystrophy.