Patients with rare epilepsy aphasia share mutations on same gene

Some patients with a rare type of epilepsy called epilepsy aphasia have something else in common. They have mutations in the same gene. Epilepsy aphasia disorders are characterized by seizures and speech abnormalities.

University of Washington researchers headed a recent study on genetic association. Their report, "GRIN2A mutations cause epilepsy-aphasia spectrum disorders," is published in the Aug. 11 issue of Nature Genetics.

The scientists sequenced genes in 519 patients with severe seizure disorders. Within the group, 44 patients had epilepsy aphasia and four of those -- or 10 percent -- and their affected family members had mutations in the GRIN2A gene.

"For a long time, people have debated whether this type of epilepsy had a genetic component, mostly because so few families have the disorder. To find a genetic cause is really interesting," said Gemma Carvill, senior fellow at the UW Department of Pediatrics, Division of Genetic Medicine, and the lead author of the study.

Carvill said to find 10 percent of patients with a genetic mutation for a particular epilepsy disorder "is quite sizable."

"In the families we looked at, multiple individuals were affected with epilepsy aphasia and all had a mutation in GRIN2A," she said.

Heather C. Mefford, assistant professor of pediatrics, said clinical testing for this gene could be done for individuals with epilepsy aphasia disorders who are wondering if they will pass on epilepsy to a child. In families with a mutation in GRIN2A, the risk of passing on a genetic mutation carrying the disorder is 50 percent.

Mefford said two other studies report similar findings.

Mefford said a lot of work is being done now to identify genes that cause epilepsy, Researchers know about only a small percentage of genes that, when mutated, result in epilepsy.

"The thought is there is probably a large number of genes with mutations that could cause epilepsy.

"We now have the tools to look for genetic mutations in large numbers of patients to identify the genetic cause," said Mefford.

UW researchers collaborated with Ingrid Scheffer and Sam Berkovic, at the Epilepsy Research Centre at the University of Melbourne, which has been collecting DNA on epilepsy patients for a long time. Other UW investigators contributing the study were Jay Shendure and Brian O'Roak from the Department of Genome Sciences, and Joe Cook, Adiba Khan and Eileen Geraghty from the Department of Pediatrcs.