Scientists have linked an epileptic gene to severe migraines

Scientists at Northwestern University (USA) have found that mutations in the SCN2A gene, previously associated with epilepsy and neurodevelopmental disorders, including autism, can also cause familial hemiplegic migraine, a rare and severe form of the disease in which half of the patient's body temporarily fails. The study was published in the journal Brain.

"Patients with this type of migraine have a dramatic symptom before the onset of the headache: they lose the ability to move muscles in half of their body — this can be very frightening. And often this condition is mistaken for a stroke until the opposite is proven," said Alfred George, one of the lead authors of the work, head of the Department of Pharmacology at Northwestern University.

To find new genetic causes of the disease, scientists studied a large family of four generations in which hemiplegic migraine was inherited. Genome—wide analysis and exome sequencing indicated a single candidate, the SCN2A gene encoding the Nav1.2 neuronal sodium channel, which plays a key role in the electrical activity of the brain. A rare mutation in this gene was present in all sick family members and was absent in healthy relatives.

To verify the finding, the researchers additionally examined other families with several affected members, as well as about 600 unrelated patients with hemiplegic migraine who did not have mutations in already known disease genes. As a result, two more rare variants of SCN2A were discovered. None of the three variants has previously appeared in large databases of population genetics, which strengthens the arguments in favor of their causal role.

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Electrophysiological experiments have confirmed that all three mutations change the response of the sodium channel to voltage and the rate of its activation. Computer simulations have shown that altered channels make neurons hyperactive — they become more easily excited and stay in an excited state longer. It is this mechanism, according to scientists, that triggers hemiplegic migraine attacks.

According to George, the discovery adds SCN2A to the list of ion channels associated with migraine, and confirms that migraine is fundamentally an excitability disorder of the brain. The finding may improve genetic diagnosis and patient counseling, and in the long term, give impetus to the development of new treatment methods.

The SCN2A gene has been studied by George's group for more than 20 years. Researchers have already established its connection with epilepsy in newborns and autism. Familial hemiplegic migraine is a rare hereditary disease in which migraine attacks are accompanied by temporary unilateral paralysis or limb weakness. Known genes explain less than one in five genetically diagnosed cases of the disease, which for a long time left most patients without a molecular diagnosis.

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Olga Butenko, a pediatric neurologist at the Medin Medical Center, said on March 26 that epilepsy attacks can occur in different areas of the brain, which affects movement, speech, memory and other functions. The causes of epilepsy can be different, including genetic characteristics, injuries, strokes, and brain tumors.