Background
The Epilepsy Genetics Group has been studying the inheritance of seizures in families and twins for over a decade. By mid-2007 approximately 8000 people have participated in our research studies.
Although epilepsy can be acquired in some people (through a bad head injury for example), there is strong evidence that genetics may cause or contribute to many types of epilepsy. For example it is more common for identical twins to both experience seizures than for non-identical twins, and there is often a family history of epilepsy or seizures in patients with certain types of epilepsy.
By 2006 there were twelve known "epilepsy genes", and our group is proud to have been involved in the identification of eight of these. However, despite these findings, relatively little is known about the genetic causes of epilepsy in most people. The genes that have been identified so far either cause very rare types of epilepsy or are rare causes of the more common types of epilepsy. In addition, we believe that the common genetic epilepsies are caused by a number of genes acting together, making it much harder to identify each individual gene.
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How do we study the genetics of epilepsy?
Twins
Twins do not have a greater chance of having epilepsy that the general population, but twins can provide special insights into the causes of epilepsy. Because identical twins share the same genes, and all twins typically share the same environment, studying twins where one or both have seizures or epilepsy can help us distinguish genetic causes of epilepsy from other causes.
Families
Most known epilepsy genes have been identified by studying families where there are a large number of people who have had a seizure at some time. While these families give us the best chance of finding these genes, they are quite rare. We also study smaller families where there are only a few people who have had seizures, and also individuals with no family history at all.
In all genetic epilepsy studies it is very important to determine exactly who has epilepsy, the type of epilepsy each person has and whether everyone in the family has similar or different types. This involves conducting a detailed questionnaire with as many people from the family as possible and may sometimes involve further testing such as an EEG (brainwave reading) or MRI (brain imaging) scan. We then request a blood sample from the participants, which is sent to our colleagues in Adelaide (A/Prof John Mulley and his team) where the DNA (genetic material) is extracted and tested. In large families detailed analysis is performed to try to determine which areas of DNA are shared by all the people in the family with seizures. This tells us where to start looking for genes that may play a role in causing the epilepsy in the family. Discovery of new genes can take many years of detailed study.
The information provided by smaller families and individuals is also crucial to our study. It is often necessary to look at a large number of people to see whether changes in a particular gene could be a common or rare cause of epilepsy. We can also make educated guesses about which genes may play a role in causing epilepsy and we need to look at a large number of people to see whether each gene is, or is not, relevant.
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What happens next?
Once a gene is identified we attempt to understand how it causes epilepsy. This is done by a number of methods including replicating the changes we see in the gene in simple systems (such as single cells) or in whole animals. We have a group of talented collaborators at the University of Melbourne, the Howard Florey Institute, Monash Medical Centre and internationally who are helping us with this.
We hope that understanding how these genes cause epilepsy will lead to a deeper understanding of epilepsy and possibly new treatments. The development of new treatments may take many years, but the genetic research and the blood samples we collect are the important beginning.
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