Genetic Autism and Spontaneous Mutation

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New Mutations: Genetic Autism Is Not Always Inherited

According to a significant study at the Cold Spring Harbor Laboratory in Long Island, New York, at least 15% of children with autism have genetic mutations that are not inherited from their parents. Another study, conducted only with children who have classic autism, found an even higher rate of new ("spontaneous") mutations.

So far, says researcher Dr. J.

Sebat, there is no indication of why these mutations occur- or whether they are on the rise. It is clear, however, that these mutations are more prevalent among children with autism. Typically, developing children have only about a 1% likelihood of having a spontaneous mutation. Interestingly, Sebat says, while autistic children have mutations, they don't all share the same mutation. Instead, there are many different mutations that occur along with autism.

Genetics and Autism Versus Heredity and Autism

The most important take-home message from this study so far is that while genetics may play a big role in autism, heredity may play a smaller role. That is, while some children do inherit autism, a large number do not. Says Dr. Sebat:

The first real clinical outcome [from our research] will be diagnostic. There is a real certainty now that you could start doing routine genetic screening of autistic children for the purpose of estimating the risk of parents for having a second child with autism. Recurrence risk is on many parents' minds. If you can identify that the primary cause is a spontaneous deletion, that is likely to put you in the "sporadic" class. This is a class of families that do NOT have as high a risk of having another autistic child as those who inherited autism.

If your first child is autistic, you have a 10% chance of having another child with autism -- but that is only an average. The risk of having another spontaneous mutation will never approach 10%. Those families who do have more than one kid with autism don't have lightning striking twice: Generally, there's something in the family.

Once you have two kids affected and then you have a third and fourth -- your risk is now 50% among males!

Next Steps in Research on Genetics and Autism

Sebat's research is only one step along the way to truly understanding how genetics and autism relate to each other. Next steps will be research to investigate some of these questions:
  • Why do spontaneous mutations occur? Is the cause environmental? Does the age of the parent have any relationship to spontaneous mutations?
  • Can the different mutations associated with autism be grouped together? If so, will it be possible to do genetic testing to figure out what type of autism a child has -- and thus which treatments will be most effective?
  • Can spontaneous mutations explain why some children with autism have physical problems while others are healthy?


Sebat J, Lakshmi B, et al. "Strong association of de novo copy number mutations with autism." Science. 2007 Apr 20;316(5823):445-9.

Zhao X, et al. "A unified genetic theory for sporadic and inherited autism." Proc Natl Acad Sci U S A. 2007 Jul 31;104(31):12831-6.

Interview with Dr. J. Sebat, August, 2007.

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