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Genetic clues to epilepsy discovered by scientists

Scientists have discovered two new genes linked to severe forms of childhood epilepsy, a breakthrough reached with new genetic technology, according to a study published in the journal Nature.

Researchers say that the genetic research technique may be a highly effective way of making discoveries about other complex neurological disorders like epilepsy.

According to the Centers for Disease Control and Prevention (CDC), epilepsy affects more than 2 million people in the US. More than 300,000 of these are children under the age of 15.

This most recent research is part of a worldwide study called Epilepsy 4000 (Epi4k), analyzing DNA from 4,000 epilepsy patients and their relatives.

Researchers from Duke University Medical Center and staff from the National Institutes of Health (NIH) created a series of international research institutions named Epilepsy Centers Without Walls. The centers enabled the researchers to conduct an analysis of DNA sequences and patient information of participants.

People with epilepsy tend to suffer from recurrent seizures due to excessive neuronal discharge. Approximatey 50 million people throughout the world suffer with the condition, with the majority living in developing countries.

The researchers say that DNA and clinical data was originally collected through the NIH-funded Epilepsy Phenome/Genome Project.

Overall, within the 4,000 epilepsy patients, there were as many as 25 epilepsy-causing mutations in new and previously unidentified genes.

David Goldstein, director of the Human Genome Variation Center at Duke University Medical Center and a study leader, says: "It appears that the time for using this [genome] approach to understand complex neurological disorders has arrived.

This moderately-sized study identified an unusually large number of disease-causing mutations and provides a wealth of new information for the epilepsy research community to explore."

New childhood epilepsy genes discovered

The scientists used exome sequencing to detect the mutations in DNA sequences that could cause two forms of childhood epilepsy - infantile spasms and Lennox-Gastaut Syndrome.

The exome sequences of 264 epileptic children were compared with those of the parents, who did not have the neurological disease. To identify any disease-causing mutations, the researchers analyzed the sequences using various statistical tools.

The results of the study revealed disease-causing mutations in six genes, four of which had been uncovered before in previous studies, but two were discovered for the first time.

Randall Stewart, a program director at the NIH's National Institute of Neurology Disorders and Stroke, says:

"Unlike some diseases, many of the genetic mutations associated with severe childhood epilepsies appear to be new mutations that are not inherited."

The researchers say that by using "novel genetic analysis techniques," they also revealed that epilepsy-causing mutations in humans are concentrated in genes that are intolerant or highly sensitive to changes in their DNA sequence.

They add that the genes are so sensitive that the smallest change in their DNA sequence means the gene may not work, which could lead to death or severe forms of diseases.

Improved drugs and treatment for neurological disorders

Following this research, the scientists also wanted to discover more genes that are likely to have epilepsy-causing mutations. They analyzed thousands of exome sequences of healthy volunteers involved in the National Heart, Lung and Blood Institute Exome Sequencing Project.

Results showed that up to 90 genes could carry epilepsy-causing mutations, and many of these have been previously linked to other neurological disorders, such as autism.

Dr. Goldstein says that further studies may discover more disease-causing genes:

"One of the most encouraging aspects of this study is that we're beginning to see how best to interpret and make effective use of exome sequence data."

He adds: "We anticipate that further studies will identify many new disease-causing genes and we intend to develop a watch list of the genes which summarizes their clinical characteristics in way that will be helpful for doctors, patients, and researchers."

Dr. Goldstein says it is clear a few pathways may be responsible for many severe pediatric epilepsies, which could mean that understanding epilepsies could be more manageable and lead to improved drugs and other therapies.

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