'Epilepsy in a dish': Stem cell research reveals clues to disease's origins and may aid search for better drugs

July 25, 2013 A new stem cell-based approach to studying epilepsy has yielded a surprising discovery about what causes one form of the disease, and may help in the search for better medicines to treat all kinds of seizure disorders.

The findings, reported by a team of scientists from the University of Michigan Medical School and colleagues, use a technique that could be called "epilepsy in a dish."

By turning skin cells of epilepsy patients into stem cells, and then turning those stem cells into neurons, or brain nerve cells, the team created a miniature testing ground for epilepsy. They could even measure the signals that the cells were sending to one another, through tiny portals called sodium channels.

In neurons derived from the cells of children who have a severe, rare genetic form of epilepsy called Dravet syndrome, the researchers report abnormally high levels of sodium current activity. They saw spontaneous bursts of communication and "hyperexcitability" that could potentially set off seizures. Neurons made from the skin cells of people without epilepsy showed none of this abnormal activity.

They report their results online in the Annals of Neurology, and have further work in progress to create induced pluripotent stem cell lines from the cells of patients with other genetic forms of epilepsy. The work is funded by the National Institutes of Health, the American Epilepsy Society, the Epilepsy Foundation and U-M.

The new findings differs from what other scientists have seen in mice -- demonstrating the importance of studying cells made from human epilepsy patients. Because the cells came from patients, they contained the hallmark seen in most patients with Dravet syndrome: a new mutation in SCN1A, the gene that encodes the crucial sodium channel protein called Nav1.1. That mutation reduces the number of channels to half the normal number in patients' brains.

"With this technique, we can study cells that closely resemble the patient's own brain cells, without doing a brain biopsy," says senior author and team leader Jack M. Parent, M.D., professor of neurology at U-M and a researcher at the VA Ann Arbor Healthcare System. "It appears that the cells are overcompensating for the loss of channels due to the mutation. These patient-specific induced neurons hold great promise for modeling seizure disorders, and potentially screening medications."

With the new paper, Parent, postdoctoral fellow Yu Liu, M.D., Ph.D. and their collaborators Lori Isom, Ph.D., professor of Pharmacology and of Molecular and Integrative Physiology at U-M, and Miriam Meisler, Ph.D., Distinguished University Professor of Human Genetics at U-M, report striking discoveries about what is happening at the cell level in the neurons of Dravet syndrome patients with a mutated SCN1A gene.

They also demonstrated that the effect is rooted in something that happens after function of the gene is reduced due to the mutation, though they don't yet know how or why the nerve cells overcompensate for partial loss of this channel.

And, they found that the neurons didn't show the telltale signs of hyperexcitability in the first few weeks after they were made -- consistent with the fact that children with Dravet syndrome often don't suffer their first seizures until they are several months old.

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'Epilepsy in a dish': Stem cell research reveals clues to disease's origins and may aid search for better drugs