Researchers at the McGill University Health Centre (MUHC) have identified a gene underlying a common form of epilepsy. The research, co-authored by Patrick Cossette, is a collaborative study that also includes investigators from the University of Toronto and Université de Montréal. Results from this work will be published in the June issue of Nature Genetics. The principle investigator is Dr. Guy Rouleau MUHC neurologist and professor of neurology and neurosurgery at McGill University.
The MUHC study analyzed DNA from 14 members of a Quebec family, eight of whom have juvenile myoclonic epilepsy (JME). Rouleau and collaborators found that the family members with JME had a mutation in a particular gene, the alpha 1 subunit of the GABAA receptor. This gene was not mutated in the unaffected family members. "The GABAA receptor is important for controlling the electrical activity in the brain," says Rouleau. "We determined that the mutation affects the function of the GABAA receptor which results in abnormal electrical patterns."
Epilepsy is a lifelong, disabling disorder that affects brain function. It is characterized by seizures that are caused by excessive electrical discharge in the brain. If the seizures are severe, brain damage or patient death may occur. Approximately, 1 out of 100 Canadians have epilepsy and about 3,200 children under the age of ten are diagnosed with this disorder each year in Canada. Most patients with epilepsy are treated throughout their lives with drug therapy, which may have severe side effects.
"Treatment for epilepsy may not work for everyone and there is a need for new therapy. Identifying and characterizing the genes that cause epilepsy will help in designing more specifically targeted drugs for this disease," says Rouleau.
For further information please see the attached Nature Genetics press release.
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NATURE RESEARCH JOURNALS PRESS RELEASE
DATED 30 APRIL 2002
**********NATURE GENETICS (http://genetics.nature.com)*********
SCIENTISTS IDENTIFY GENE UNDERLYING COMMON FORM OF EPILEPSY
The identification of a gene underlying juvenile myoclonic epilepsy (JME)--a first for one of the classical' epilepsy syndromes--is reported in Nature Genetics. The classical epilepsies are common neurological disorders that affect approximately 0.4% of the population, with those affected by JME making up about one-quarter of those.
Whereas a few mutated genes have been shown to be associated with rare forms of epilepsy, the variability in clinical features of the common epilepsies has hampered the search for the genetic bases of these syndromes. To circumvent this problem, Guy Rouleau and colleagues identified a unique French-Canadian family in which eight individuals have a similar set of symptoms that are consistent with JME.
They screened all 14 members of this family and found identical mutations in a well-characterized gene, GABRA, in the 8 individuals who have JME. The 6 family members who are unaffected did not carry the mutation. This gene encodes a subunit of a chloride channel (the GABAA receptor) that is involved in the transmission of signals between neurons. The authors confirmed that the mutation alters the function of the channel by showing that the mutant protein has diminished activity in cultured cells.
It was previously shown that mutations in a different subunit of the GABAA receptor, are involved in a different form of epilepsy that is accompanied by fever-induced seizures. The present study, in which the GABAA receptor is implicated in a distinct and more common form of epilepsy, suggests that this molecule may be centrally involved in these syndromes. As there are 16 different subunits that can contribute to a functional GABAA receptor in the brain, the screening of families for mutations in each may yield further insight.