Genetic Cause for Childhood Absence Epilepsy Identified
June 2, 2008 by Kristina Chew, PhD
Filed under Genetics, Health, Neuroscience
More genetics news today: Researchers have identified the mutated gene that causes childhood absence epilepsy (CAE).
The seizures of childhood absence epilepsy (CAE) are usually staring spells during which the child is not aware or responsive. The child’s eyes may roll up briefly. Each spell lasts about 10 seconds and ends abruptly. The child often is not even aware that anything has happened. These episodes can occur 1 to 50 times per day, often during exercise. Tonic-clonic (grand mal) seizures, with or without fever, may occur for a while before absence seizures develop and may occur from time to time thereafter. [Epilepsy.com]
The Childhood Absence Epilepsy Family Study also notes that CAE is also known as “Petit Mal” or epilepsy with “staring spells.” CAE is an inherited disorder and accounts for 10-12 percent of cases of childhood epilepsy.
The new study that points to a genetic cause for CAE appears in the May 29th online edition of the American Journal of Human Genetics. The study’s authors are from the David Geffen School of Medicine at UCLA and the Epilepsy Genetics/Genomics Laboratory, Epilepsy Center at the VA-Greater Los Angeles Healthcare System in West Los Angeles.
UCLA/VA research scientist Dr. Miyabi Tanaka studied the DNA of 48 patients with CAE and discovered that four patients had a genetic mutation occurring in a receptor called GABAR which binds to a neurotransmitter of the brain called GABA that inhibits the excitation of nerve cells in child and adult brains. When this regulation is lost or reduced, seizures develop.
“We identified this genetic mutation in eight percent of study patients with CAE, which is significant,” said Richard W. Olsen, Ph.D., study author and professor, Department of Molecular and Medical Pharmacology, David Geffen School of Medicine at UCLA.
Scientists also found that the genetic mutation was caused by an “alternative signal peptide called exon 1a, which is richly expressed in the fetus and developing brain, but as the child matures and becomes an adult, the expression of exon 1a is reduced”—-and this is why CAE “disappears” in adolescence and in adults.
We have wondered about the possibility of my son having seizures like the “absence seizures” noted above. Charlie’s pediatric neurologist specializes in epilepsy and seizures and (based on our descriptions of Charlie’s behavior) does not think he is having these types of seizures. Since my son’s language is very limited, we can never be 100% certain about anything, though—-hence the continuing interest in the possibility of medical signs and/or tests to detect conditions; to find answers.
Jeff Stimpson
Jill Cornfield