In a study in the
journal Cell, scientists checked for variations in the CHD8 gene of 3,730 children
with autism or developmental delay. They identified eight people carrying
mutations in the gene, but no mutations were found in the control group of
around 9,000 unaffected children, indicating a strong link to autism despite the small numberof carriers.
The children with the mutation share similar clinical
characteristics. They have wide set eyes and large foreheads, and most have
trouble sleeping and gastrointestinal problems. In the study, the researchers
combined their observations of these children with clinical reports of another
seven children with the same autism subtype.
got a clear cut case of an autism-specific gene', said Dr Raphael
Bernier, the lead author and clinical director of the Autism Center at Seattle
Children's Hospital in the USA. 'This will be a game changer in the way scientists
are researching autism'.
the role of the mutant version of CHD8,
the team worked with scientists at Duke University in the USA who study zebrafish. When they
disrupted the gene in the zebrafish, they developed large heads, wide set eyes
and were constipated - similar to the symptoms observed in the affected individuals.
developmental disability that affects behaviour and social interaction, is complex
and manifests itself to varying degrees and may have many subtypes. Researchers
have traditionally tried to distinguish different subtypes based on behavioural
differences. But as Dr Bernier told Scientific American: 'We've tried for so long to
identify subtypes of autism based on behaviour alone and we've done abysmally at
The researchers involved in the study say that the reverse
approach — investigating patients who carry identical genetic mutations and seeing
if their symptoms also cluster — could prove more fruitful, especially when it
comes to designing specific treatments.
in the past have suggested that most cases of autism cannot be put down to
one genetic mutation. Rather, a large variety of different types of genetic
variations, perhaps with chromosome rearrangements or copy number variations may
work in concert. An environmental role is also hotly debated.
the most important realisation is that not all autisms are created equal', Dr
Evan Eichler, who was in charge of the genetics side of the study, told
The researchers are now looking for more people
with CHD8 mutations, hoping to
further characterise the link between the gene and autism. They have access to
a worldwide genetic database of 15,000 people with developmental disorders with
permission to contact affected families.