Autism is understood more and more to be a genetic disorder; to many, the word “genetic” implies that autism is inherited from one’s parents. A new study focuses on de novo (spontaneous; present in the child but not in his or her parents) mutations rather than on inherited mutations. Research published in the March 16th Science magazine has “found a distinction between heritable and sporadic forms of the disease,” as a press release from Cold Spring Harbor Laboratory announced today.
“Sporadic” cases of autism are those in which there is no history of autism in the family. Using high-resolution method for analyzing DNA called microarray technology, the researchers found that many autistic children have spontaneous (de novo) copy number mutations in their DNA, and that these gene mutations occur more often in cases of sporadic autism rather than in familial (heritable) cases or in children who do not have autism. 264 families participated in the study. An article in the March 15th The Scientist provides more details:
The study found that 10% of children (12 out of 118) with sporadic autism had de novo copy number variations, whereas only 1% of controls (2 out of 196), who had no history of autism, showed CNVs. Among families with multiple autistic children, only 2% (2 out of 77) autistic children showed differences in copy number from their parents.
The researchers plan to screen more than 2000 families over the next three years. Most genetic studies of autism have been of families who have multiple autistic children; scientist Jonathan Sebat notes that “‘sporadic autism is genetically distinct from the type that runs in families’” and therefore is to be treated differently.
The results strengthen the scientific basis for using microarray technology for diagnostic testing. Methods for detecting spontaneous mutations will provide important information for children with autism and their parents. This information could help to determine the risk of having a second child with autism, and the knowledge of which genes are involved may lead to the development of new therapies.
My understanding of this study on gene mutations in autistic children is that my son Charlie would qualify as a case of “sporadic.” He is our only child with autism, and also our only child. I am wondering if relatives on the autism spectrum who are not part of one’s immediate family might also be considered: Does having an autistic cousin, for instance, mean that one’s autism is still completely sporadic? What if families were screened in which there was one autistic child and an autistic parent (see Autism Diva on the BAP or broader autism phenotype, “the condition of having just a touch’ of autism that is frequently found in the parents and other close relatives of autistic kids”). Again, Charlie is our only child; we chose only to have Charlie, so the possibility remains that Charlie could have had an autistic sibling.
The researchers note that their work may influence diagnostic testing and also treatments for autism. This research was primarily funded by the Simons Foundation, whose 2007 Autism Research Initiative notes that its mission is to “understand the causes of autism and thereby improve the diagnosis, treatment, and prevention of this and related developmental disorders.” And thinking it over tonight—as I am preparing a presentation on teaching autistic college students and Charlie ran excitedly through the house when his teacher came for a visit, cried and cried when I asked him to wait till the garbage can was full before taking it out, and asked for “Sesame Street book” after spotting the program for a musical show he saw last year tucked behind a shelf—reflecting on all this, I really cannot imagine a world without Charlie, without Charlie as he is today.
However Charlie came to be—whatever mutations, deletions, variations of genes brought him into being—it is a good thing that they did.