Brain/Body study

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New Autism Gene Doubles Risk

Finding Suggests Autism Is Disease of Brain and Body By DeNoon

WebMD Medical News Reviewed By Louise Chang, MD

on Monday, October 16, 2006

Oct. 16, 2006 -- A single gene mutation doubles a child's susceptibility

to autism, a Vanderbilt-led research team reports.

It's a discovery with far-reaching implications. Why? It isn't

specifically a brain gene. In fact, it affects multiple systems in the

body, including immune function and gut repair. The gene in question is

a variant form of a gene called MET.

This suggests that the complex set of behaviors and mental disabilities

we call autism may not, as previously thought, be solely a problem with

brain development. It may also be linked to subtle developmental

problems throughout the body.

The study, which included Pat Levitt, PhD, of the Vanderbilt Kennedy

Center for Research on Human Development, appears in the early online

edition of the Proceedings of the National Academy of Sciences.

" We hypothesize that the common, functionally disruptive [MET gene

variant] can, together with other vulnerability genes and [genetic] and

environmental factors, precipitate the onset of autism, " Levitt and

colleagues suggest.

New Autism Gene Important

Kids with autism usually seem normal at first. Then they seem to

backslide, losing abilities they once had and suddenly withdrawing into

their own world.

There are many theories about why this happens. Clearly, something goes

wrong with normal development.

The MET gene, Levitt and colleagues note, encodes an important enzyme

called the MET receptor. Among other things, the MET receptor sends out

signals important for brain growth, brain maturation, immune function,

and gut repair.

Many parents of children with autism report that their kids have

digestive problems and haywire immune responses. It's never been clear

whether this is directly or indirectly linked to their autism.

Linking the MET gene to autism opens the door to exciting new research,

notes W. State, MD, PhD, director of the neurogenetics program

at Yale University. State's editorial accompanies the Levitt team's report.

" The possibility that a MET variant might lead to immune dysfunction and

gastrointestinal disturbance along with autism-spectrum disorders is an

important question to pursue and one that will likely lead to some

debate, " State writes.

That's because the first theory to link autism, gut problems, and immune

dysfunction blamed these symptoms on childhood immunization with the

measlesmeasles/

mumpsmumps/rubella (MMR) vaccine.

That theory -- now rejected by all but one of the researchers who first

proposed it -- holds that kids who develop autism are particularly

sensitive to the toxic effects of thimerosol, a form of mercury used as

a vaccine preservative.

The thimerosol theory was rejected by an Institute of Medicine panel of

experts. Now the MET gene may reopen investigation into the link between

autism and other developmental problems.

" The very important question of whether and how gut disturbance,

regression, and immunological issues may be related has been, in part,

obscured by this [thimerosol] controversy, " State writes. " Hopefully,

the present study will lead to additional rigorous investigations of

these questions without fueling unnecessary concern regarding MMR. "