Wednesday, March 28, 2007

The "Raising Arizona" theory of autism?

A new study using new imaging techniques has discovered missing and/or extra pieces of DNA in cases of autism where the disorder cannot be genetically traced to the parents. Strangely, I couldn't find this article in the online version of Science Magazine. I'd like to read the study before I draw any conclusions from it, but it sounds as if it might give some support to my personal theory that there are different causes for autism, some genetic, some possibly not. This blurb makes it sounds as if the authors concluded that the DNA quirks arose spontaneously in the father's semen or the mother's egg, soemthing that sounds, well, quirky. I'd have to see that spelled out. It reminds me of that character in "Raising Arizona" who couldn't sire children because of his bad semen. In any event, that seems to beg the question what caused the DNA anomalies, whether they arose in the parents' reproductive material or in the children themselves. That the question is begged would seem to lend support to the theories that some cases of autism have environmental causations:

New Gene Mutations Linked to Autism
By Erik Stokstad
ScienceNOW Daily News
16 March 2007

Autism has been a frustrating puzzle for geneticists. Searching for genes involved in the disorder, they have focused mainly on the 10% of cases that seem to be inherited. Now a group has made progress toward figuring out what goes wrong in the other 90%, the so-called sporadic cases.

Led by Jonathan Sebat of Cold Spring Harbor Laboratory in New York, the team looked at DNA from 264 families. Using a variety of techniques, the researchers scanned the genetic material for so-called copy number variants, in which relatively long stretches of DNA are lost or gained. Sebat and colleagues found these defects in about 1% of the 196 people without autism they tested. The rate was 10-fold higher among 112 sporadic cases (people who were the only ones in their families with autism). In contrast, copy number variants turned up in just 2% of 47 families with multiple cases of apparently inherited autism, the team reports today in Science. When the researchers further tested the families with a single case, they found that the parents did not have the mutation, suggesting that the mutations were not inherited but had arisen spontaneously in mom's egg or dad's sperm.

Sebat estimates that at least 15% of cases of autism and closely related disorders are due to these kinds of mutations. And he expects that fraction to rise considerably when the team continues the research on more families and with more sensitive DNA probes--work that will also help pin down the genes involved. "Increasing our resolution and sample size is going to give us a better idea of where the major players are," he says.

In the meantime, the finding could be useful for parents with an autistic child who worry that the disorder is inherited in their family and that future children will also be autistic. "If a [spontaneous] deletion is identified, the recurrence risk seems greatly reduced," says Linda Brzustowicz of Rutgers University in New Jersey.

Edited to add: Thanks to gentle reader Ros, Ph.D., I have paroused a copy of the report. It looks like good research to me, and, as I said previously, raises questions about what might cause spontaneous deletions. I wonder whether hospital genetics departments will obtain the imaging technology to conduct these tests when a child is diagnosed with autism so that parents can make informed decisions on how to proceed with future procreation. Probably not.

On a personal note, we went in for genetic counseling after our first son was diagnosed but before the second son was diagnosed. The doc told us that we had a 5% chance of our second child having autism (he does) and a 10-12% chance of any third child having the disorder. I joked afterwards that "genetic counseling" is a euphamism for "get yourself fixed," which is what I did shortly after our second autism diagnosis. It seemed like it would be irresponsible and unfair to create another life knowing in advance there was a very good chance that the child would be born with a potentially lifelong, severe disability.


Ros said...

If you don't have access, I can email you the pdf.

Ros said...

oops, just re-read your post. You know were Science is parked on the web.

I think this is a science express article. This means that it will generate enough interest that it is released online before it comes out in print. Only people with individual (not institutional) subscriptions can access the pre-published material. I am a geek and it so happens that I have a subscription. I can get you the pdf if you are interested.

Randy said...

Ros, I'm very interested. There's an e-mail addy on my blogger profile. If you could send me that pdf version of the article, I'd greatly appeciate it.

Ros said...

Ok, sent it your way. Let me know if you have any troubles getting it.