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stranger_in_a_strange_land's avatar

Is there a genetic marker for Autism Spectrum Disorders?

Asked by stranger_in_a_strange_land (18335points) December 16th, 2009

I was diagnosed with Aspergers Syndrome (in the autism spectrum) about two years ago. Since then I have been reading everything I can get my hands on about the topic.

Experts believe that autism spectrum disorders are an inherited condition. From my reading (I’m not a biologist or geneticist) I understand that the condition has not been traced to single-gene mutation or single-chromosome abnormality.

Has a marker pattern, or combination of markers been discovered that directly points to or labels ASD? What is the likelihood of a genetic test being developed that either gives a probability of an individual or couple producing ASD offspring or an in-utero test such as for Downs Syndrome?

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sndfreQ's avatar

We had the tests done and yes there are genetic markers…PM me and I can look up the test for you (honestly, my wife is the more knowledgeable one on the subject, so I’ll have to wait until she wakes up to get you the answer and references).

dpworkin's avatar

There are markers that have a positive correlation, but be aware that it is a distinctly polygenic phenomenon and by no means are all factors and combinations known, and also, as I am sure you are well aware, it is a spectrum disorder, presenting on a broad continuum, so that merely identifying certain markers does not make a prognosis. However, there does seem to be some reason for early optimism.

King_of_Sexytown's avatar

A friend of mine has two boys by different fathers who are both autistic to some degree. She had a test done to see if she was the carrier. Cos that sort of thing can be done if that is what you are asking. They know enough that they can tell who is likely to have autistic kids and then the kids can be watched so if treatment is needed it can be caught and given early.

sndfreQ's avatar

@pdworkin that is correct, as the “spectrum” is broad-based, and is characterized by many factors, including genetics. As ASD has such a broad spectrum, the combination of factors the diagnosis comes from identification of one or more factors in concert; I’m sure this group is aware of them, but for laypersons, there are several (I may not be listing them all either-there are a couple dozen):

-Genetic markers/predispositions (for example, the inability to flush/excrete toxins, esp. heavy metals, for example, the Mercury (Thimerasol) that is a preservative in vaccinations);
-Diet/Allergies (intolerance to lactose, glutens, proteins, etc.);
-“Leaky Gut” syndrome/digestive issues related to allergies/intolerance;
-Other metabolic issues (e.g. cellular disorders that cause oxidative stress, Methylation imbalances, etc.);
-Blood-brain barrier trauma (viral infections, exposure to certain viruses via pediatric vaccinations like Measles);

It’s the very thing that causes the “spectrum” and why most identify ASD with the icon of a “jigsaw puzzle”-it’s a very complex set of circumstances, which produce very specific and unique symptoms-some treatable, some curable, others that need to be accommodated for in making life adjustments, and cognitive and behavioral therapies to mitigate the social and behavioral effects of the disorders.

The thing that pisses me off most about this is not the circumstances, but the unwillingness for our government, big Pharma, and the medical industry to acknowledge the truths and facts for what they are and to treat this like any other medical epidemic.

When the parent knows more than the pediatrician, when therapies are being cut from regional services like SELPA because some bureauocrats don’t believe in their efficacy, that’s what starts to push my buttons.

\rant

nikipedia's avatar

If I understand correctly, there are a number of genes that each confer some degree of susceptibility to austim spectrum disorders, and we have only identified a few of them so far. And to make the story even more complicated, epigenetic influences seem to play a role, too. A paper came out this past October showing that either a deletion of genes involved with oxytocin receptor expression, or methylation at that site [link opens pdf] is associated with autism. But even in that paper, this was only the true in 1 case out of the 119 included in the study.

Here’s a summary of genes that have been implicated from a review published in 2004. There have been more genes identified since then:
Thus far, a putative speech and language region at 7q31-q33 seems most strongly linked to autism, with linkages to multiple other loci under investigation. Cytogenetic abnormalities at the 15q11-q13 locus are fairly frequent in people with autism, and a “chromosome 15 phenotype” was described in individuals with chromosome 15 duplications. Among other candidate genes are the FOXP2, RAY1/ST7, IMMP2L, and RELN genes at 7q22-q33 and the GABA(A) receptor subunit and UBE3A genes on chromosome 15q11-q13. Variant alleles of the serotonin transporter gene (5-HTT) on 17q11-q12 are more frequent in individuals with autism than in nonautistic populations. In addition, animal models and linkage data from genome screens implicate the oxytocin receptor at 3p25-p26.
From the journal Pediatrics.

So I think what scientists are looking for right now is not a specific constellation of genes, but instead looking for the individual genes that each seem to play a role. I suspect (although I don’t know for sure) that identifying a genetic pattern would be extreeeeeemely difficult: genetic studies in general are very hard to carry out because of the massive quantity of data carried by a single genome. So finding a meaningful pattern across many genomes becomes mathematically very difficult due to the sheer size of the data set.

That said, I think genetic tests are probably not far off. You could probably get a company like 23andMe to search for some of the genes that have already been found. But a meaningful test with interpretable results… who knows when that’ll be.

sndfreQ's avatar

Awesome insights and info @nikipedia ! Thanks and Lurve!

jerv's avatar

The shortest thing I can think of to add is this: if it were that simple then you and I would be diagnosed by blood test, not psychologists/psychiatrists.

The truth it that right now they are not sure. All evidence points to certain genes, but the fact that Autism manifests in so many different ways means (for instance, you and I are fluent in at least one language and don’t spend most of our day just sitting there rocking) that researchers have an even harder time trying to pinpoint certain genes.

It’s less of “Here are the genes for autism” and more like the Electron Cloud theory of atomic structure; an area of probability rather than a direct cause-effect relationship. It is also possible for one twin to have some form of ASD while their identical twin is neurotypical.

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nikipedia's avatar

Aw, you guys are too kind :)

augustlan's avatar

[mod says] Off topic, personally identifiable information has been removed.

King_of_Sexytown's avatar

I don’t even remember what I said

stranger_in_a_strange_land's avatar

@jerv I like that Electron Cloud analogy. That seems to be the way research will have to go. +GA

stranger_in_a_strange_land's avatar

@pdworkin Thanks for you’re earlier summary, +GA

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