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Genetic Defect Linked To Epilepsy

January 14, 2009

Scientists find link between genetic defect on chromosome 15 and epilepsy

In a research published in the advanced online publication of the scientific magazine Nature Genetics, researchers have identified a genetic defect for common epilepsies on chromosome 15. A subset of the patients with epilepsy lacked a certain part of this chromosome. Further studies on patients from the USA confirmed this finding. The loss of small chromosomal segments, called microdeletions by geneticists, has previously not been connected with common disorders that also include many types of common epilepsies.

Dr. Ingo Helbig, University of Kiel and Department of Neuropediatrics at the University Medical Center Schleswig Holstein, Germany, is first author on this research study: “So far, we didn’t know that microdeletions, loss of entire chromosomal segments including several genes, can also be a cause for common diseases. This finding will help understand why people suffer from common disorders including epilepsies.”

Up to three percent of the population experience epileptic seizures and one percent suffers from epilepsy, which is characterized by recurrent seizures. The researchers hope that understanding how this genetic defect leads to epilepsy will help develop new drugs against seizures. So far, most genes for epilepsy were only found in rare form of epilepsies. However, hereditary factors are long known to play a much larger role, contributing to many common forms of seizure disorders. Hence, the discovery of the 15q13.3 microdeletions in common epilepsies is an important milestone.

44 coauthors contributed to the recent study, which was coordinated by Dr. Thomas Sander from the Cologne Center of Genomic at the University of Cologne, Germany. On a European level, this project included German groups from Berlin, Bonn, Marburg, Ulm as well as groups from Vienna, Copenhagen, Utrecht (NL), Geneva, Troina (Italy), Marseille and Nice. The research study was performed in collaboration with the group of Dr. Evan Eichler at the Department of Genome Sciences and Howard Hughes Medical Institute at the University of Washington, Seattle. Dr. Eichler is one of the pioneers of research on microdeletions in human disease.

Many authors on this research papers are part of the European EPICURE project of the European Union, a large consortium dedicated to the research of epilepsies.

Image 1: Prof. Ulrich Stephani at the University Medical Center Schleswig-Holstein, Germany is taking the medical history from a young patient with epilepsy from Kiel. Using EEG monitoring, brain waves are constantly monitored in order to detect epileptic seizures. Using this information, physicians can find regions in the brain, which cause epileptic seizures. In many cases, however, seizures affect both sides of the brain and are called “generalized” epilepsies. Particularly in generalized epilepsies genetic factors such as the recently identified 15q13.3 microdeletion are found to play an important role. Copyright: UK SH

Image 2: The EEG record the activity of the brain helping physicians and researchers understand the form of epilepsy that the patient suffers from. In the recent publication on microdeletions in epilepsy, researchers focused on so-called Idiopathic Generalized Epilepsies, which show a specific EEG pattern. This pattern is characterized by sudden rhythmic discharges (right half of the picture) that can be recorded at the same time over both sides of the brain. Copyright: UK SH

Image 3: Using hundred thousands of markers are used to measure the intensity at specific spots in the human genome. A sudden drop of signal intensity (red bar) in certain parts of a chromosome suggests that a small part of genetic material is missing. In the recent publication, researchers have used modern computational tools to scan the genomes of patients and unaffected controls for the presence of microdeletions on chromosome 15. Microdeletions were only found in patients with epilepsies and not in controls. Copyright: UK SH

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