Researchers at the University of Washington, US, have found that different genes may be responsible for causing autism in boys than girls. Reporting in the Journal of Molecular Genetics last week, they have found evidence for two genetic subtypes of autism; both male versus female and also the early versus late onset form of the disorder. The study provides new evidence that multiple genes contribute to autism.
Professor Geraldine Dawson, a Professor of Psychology and a member of the team, explained that this information is critical: 'With Alzheimer's disease research, one big breakthrough was segregating the late and early onset forms of the disease, and this led to important genetic discoveries'.
Autism is a lifelong developmental disability that typically appears during the first three years of life. The disorder affects social and language skills, and the way in which a child relates to people, objects and events.
The researchers examined the DNA of 169 families with at least two siblings who met the strict criteria for autism. They also scanned the DNA of 54 other families that had members with autism and less-severe forms of the disorder such as Asperger syndrome.
Professor Gerard Schellenberg who led the study explained that they came up with 'strong support' for an autism gene on chromosome 7 and 'less, but still compelling evidence' for genes on chromosomes 3, 4 and 11. These results confirm some data from previous studies, particularly involving chromosome 7.
He continued, 'It is highly unlikely that there is only one gene responsible for autism', adding 'There may be four to six major genes and 20 to 30 others that might contribute to autism to a lesser degree', adding 'and because autism is rarer in females, it may take more risk genes for a female to have autism'.
The researchers are looking for autism susceptibility genes, ones that heighten the risk of an child getting autism, just as there are genes that raise the chance of getting breast cancer. Professor Dawson said that "once we discover these susceptibility genes, we can immediately screen infants to identify those at risk early in life. Early identification can lead to early intervention, which could have a much more dramatic effect'.
She added: "Once you understand the biology you can develop a prevention strategy including medical approaches'. The search for autism genes is part of a long term Autism Center effort to uncover the genetic and neurobiological causes of autism. The US Centers for Disease Control and Prevention estimates that up to one in every 175 US children have autism.