Many Gene Glitches May Up Autism Risk

People with autism may have more DNA mutations sprinkled
throughout their genes than those without autism, a new study shows.

The study focuses on spontaneous mutations, not inherited gene glitches that
are handed down from parent to child.

Such spontaneous mutations may affect 100 or more different genes and appear
to be "frequent" with autism, researcher Jonathan Sebat, PhD, tells
WebMD.

By screening for such mutations, "we may be able to inform parents about
their risk for having a second child with autism," says Sebat, who works at
Cold Spring Harbor Laboratory in Cold Spring, N.Y.

The study appears online in Science Express.

Autism Gene Study

Sebat's team studied 264 families, not all of which had an autistic
child.

Of the families studied, 118 families had one child with an autism spectrum
disorder, 47 families had multiple children with an autism spectrum disorder,
and 99 families had no diagnoses of autism spectrum disorders.

Participants provided blood samples. Using those blood samples, the
researchers mapped each participant's genome, their entire collection of
DNA.

The scientists looked for chunks of DNA that were duplicated or deleted.
They also checked whether those gene glitches were spontaneous mutations, which
weren't passed down from parent to child.

Many Mutations

Spontaneous DNA mutations were seen in more than 10% of the autistic
participants studied, Sebat tells WebMD.

The mutations were typically deletions, not duplications, of DNA chunks.

The mutations didn't just turn up in one or two genes. Instead, they were
found at many locations throughout the genome, and the mutations weren't the
same in every patient.

Some mutations involved more than one gene. For instance, one child with an
autism spectrum disorder had a DNA deletion that involved approximately 27
genes, the study shows.

All in all, the researchers spotted 17 spontaneous mutations in 16
participants, 14 of whom had an autism spectrum disorder.

More Than 100 Autism Genes?

"These data are consistent with the hypothesis that there are many
autism genes in the genome," Sebat tells WebMD.

He speculates that there could be "100 or more" autism genes.

The spontaneous gene mutations were typically seen in families with only one
autistic child. The genetics of autism may unfold differently in families with
several autistic children, Sebat notes.

By Miranda Hitti
Reviewed by Louise Chang
B)2005-2006 WebMD, Inc. All rights reserved