Researchers have discovered a mutant gene that causes a rare form of epilepsy in women. Known as epilepsy and mental retardation limited to females (EFMR), the condition is characterised by seizures from around the age of one, with the slowing of development and cognitive impairment, in some cases with severe mental retardation.
The mutant gene, known as PCDH19, was found on the X chromosome of female sufferers. Males can also carry the mutant gene on their X chromosome and pass it onto their children, however they do not suffer from the illness.
This is an interesting phenomenon which defies typical genetic coding. Usually, mutations found on the X chromosome present symptoms of disease in males rather than females. This is because female DNA contains two X chromosomes and if a mutation is found on one of the X chromosomes it is usually not found on the other, and the non-mutated X chromosome offers protection from the disease. Male DNA on the other hand contains one X chromosome and one Y chromosome, therefore a mutated X chromosome usually causes the person to be affected by the mutation and suffer from the disease.
The scientists who carried out this study are still unclear as to why men are unaffected by EFMR but believe the male Y chromosome could be protecting them from the disease.
Hope for Sufferers of Related Conditions
Until now the cause of EFMR had not been known but this new discovery is being welcomed as an opportunity to better understand related issues such as autism and obsessive compulsive disorders. The PCDH19 gene is important for cell to cell communication in the brain and scientists believe there could be a link between its mutation and other conditions. They are also excited by the possibility of offering screen testing for families affected by EFMR.
The research was carried out by the Adelaide Women’s and Children’s Hospital and University of Adelaide, Australia, alongside the Wellcome Trust Sanger Institute in Cambridge, in the UK. Seven families with subsequent generations of male carriers and female sufferers were studied across the globe, from Israel to the United States. In one family 23 women across five generations suffered from the disease.
In each family studied, researchers discovered that every woman who carries the mutant gene presents symptoms of the disease whereas any male carrier shows no presentation of symptoms. Professor Michael Stratton of the Wellcome Trust said after the recent publication of results, “identification of PCDH19 as the underlying gene will now allow diagnostic testing in families with the disease opening the possibility of prevention of further cases.”
Whilst this is a relatively rare condition, it does offer hope for sufferers of the debilitating condition worldwide and the promise of hope for sufferers of related conditions.
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