New gene identified: Involved in both intellectual disability and epilepsy

March 10, 2002

Intellectual disability and epilepsy often occur together and frequently have genetic causes. Now, for the first time, researchers from the Women's and Children's Hospital, Adelaide have identified a major gene that is responsible for both conditions.

Senior hospital scientist Dr Jozef Gecz from the Dept of Cytogenetics and Molecular Genetics says, " This gene is found on the X-chromosome and is one of probably 100 genes on that chromosome, which when mutated, can cause intellectual disability.

"The really novel aspect to this gene is its involvement in epilepsy as well as in intellectual disability.

Previously nine other epilepsy-causing genes have been identified and these belong predominantly to a specific group called 'ion channels' and they have nothing to do with intellectual disability.

"Our new gene is different, being more of a master gene, controlling how, where and when other genes work and thus contributing to the normal cognitive function of human brain.

"It will be very interesting to know the identity of these genes, that are under control of this master gene as they may potentially be involved in either epilepsy, intellectual disability, or both," says Dr Gecz, who led the team of 17 researchers from six countries collaborating on this project.

Dr Gecz and his team are puzzled by their finding that the same mutation in this gene can give rise to very different clinical outcomes.

"We studied genetic material from nine families worldwide and found the same mutations in the gene gave rise to epilepsy including infantile seizures (early childhood epilepsy) and other types of seizures, dystonia (disorder of muscle tone causing muscle contraction) as well as intellectual disability. We have no answers for why this occurs, but it is something we are keen to study further".

The research involved a worldwide collaboration with genetic material being obtained from families in Norway, Canada, Belgium, and Australia (Adelaide, Melbourne and Newcastle). However, isolation and identification of the gene was carried out in Adelaide, South Australia at the Women's and Children's Hospital.

"Our findings of mutations in this gene in the set of nine families with various clinical presentations including West syndrome, Partington syndrome, myoclonic epilepsy, syndromic and non-specific intellectual disability is quite unexpected, " Dr Gecz says.

The identification of this gene may have its biggest impact on families and isolated cases with 'non-specific' intellectual disability, which until now could only be diagnosed by delayed development and intellectual impairment. However, this still needs to be substantiated by further experiments.

Dr Gecz says the immediate benefit of this discovery is that we can now provide feedback to the affected families and thus assist them in making informed reproductive decisions.

It is estimated that up to 2% of the population suffer from intellectual disability and 2% from epilepsy.
This work is published on line on March 11, 2002 in Nature Genetics.

To arrange interviews with Dr Gecz please contact:
Dr Edna Bates
Manager, Research Communications Tel: (618) 8161 7388
mobile 0401 125 630 (after hours)

Women's and Children's Hospital, Adelaide - Part of the Children, Youth and Women's Health Service

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