Monday, August 20, 2007

Another Nail in the Coffin...

Although I have begun to despair that the "mercury-causes-autism" hypothesis can ever be killed, a recent study by Zhao et al has driven another nail into its coffin.

In their study - "A unified genetic theory for sporadic and inherited autism." - the authors describe exactly how spontaneous mutations could cause both sporadic autism (autism in families without a family history of autism) and familial or inherited autism.

You see, this has been the real mystery in autism (not the faux myteries of "poor excretion" and "mercury poisoning") - how families with inherited autism can show the same mutation in all affected members yet not have the same mutation as other families with inherited autism (for example, see here, here, here, here and here).

The answer, it appears, is that females with mutations associated with autism may be resistant to developing autism. Why this is so is not yet clear, but it has been shown pretty conclusively. These women may have one of the many mutations that cause autism but they do not develop the disorder themselves.

However, even those who don't develop autism are still carriers of that genetic mutation and (on average) 50% of their sons will receive that the mutation. Of the sons receiving the mutation, a high percentage of will develop autism. Additionally, about 50% of their daughters will also get the mutation, although only a few will develop autism (all who receive the mutation will be carriers).

This, of course, is not the entire story, but it is a reasonable lay summary of the article.

For those people who will immediately say, "Aha! It's those nasty chemicals/viruses/cell phones that are causing mutations in our children!", let me point out one thing:

The mutations are in the germ cells (i.e. sperm and eggs) of the parents of the autistic children. For these mutations to happen in a child and cause autism, it would have to happen at the single-cell stage (immediately after fertilization).

I encourage people to read the article for themselves - it's available free online. Don't just take my word for it. It's not an easy read, but even if you can't understand it all, you should come away with the idea that [a] this looks less and less like a simple case of "environmental toxicity" and [b] it is a much more complex issue than many of the autism "advocates" would have you believe.

Happy reading!


Prometheus

8 Comments:

Blogger Another Autism Mom said...

Prometheus, I confess I'm a little confused. Can males be carriers of the mutation too, without presenting autism symptoms?

You see, I can trace autism in my family starting on my grandmother (my father's side) and cousin (same side of the family), both women with Asperger's. Then I have my son with autism (high functioning).

Is my NT brother at risk of having autistic offspring?

Thank you,

20 August, 2007 14:21  
Blogger Fore Sam said...

So, it must be some genetic mutation that began at 8 years of age that started reversing the symptoms of autism and not the chelation. That makes sense, if genes can mutate to cause autism, they must also mutate to cure it. Thanks for letting me know this.

20 August, 2007 15:45  
Anonymous Mekei said...

Thanks for the simple terms Prometheus.

I'm waiting for the headline: Chinese-Made Toys Linked to Autism story to break any minute.

20 August, 2007 16:32  
Blogger Bartholomew Cubbins said...

Great post as usual. But do you think that this kind of science is going to mean anything to the mercury militia?

20 August, 2007 18:10  
Blogger Prometheus said...

Another Autistic Mom,

According to this study, males can be asymptomatic carriers as well as females. The difference is that males are more likely to develop autism (symptomatic) from the mutations, so there will be fewer male carriers and more males with autism.


Fore Sam,

You seem to be stuck on the idea that autism is a syndrome of developmental stasis. It's not! It is a syndrome of developmental delay.

If you follow any autistic child through time, you will see them make progress - some more than others.

I have seen autistic kids go from completely non-verbal and no eye contact or social interaction to being indistinguishable (on casual observation) from their "typical" peers without any of the "biomedical" interventions you are so fond of.

Likewise, I have seen autistic children get the "whole enchilada" - from DAN! to nuts - and remain non-verbal and socially isolated. Their progress seems to be completely unrelated to the "therapies" they get.

The finding that mutations in many different areas of the genome can cause autism explains much of the diversity we see in autistic children - and in autistic adults. It may be more useful to think of autism as a symptom than as a disorder.

Bart,

As Fore Sam so kindly demonstrated, the "true believers" aren't going to be persuaded by anything. Not science, not reason, not even if God himself wrote it in big letters in the sky.

My purpose is to provide an alternative viewpoint for people who haven't made up their minds yet - people who can still be reached by reason.

Mekei,

I'm sure that headline is coming. It's just that Dan Olmsted is in the process of moving to a new office. Just wait, he'll get to it as soon as he can.


Prometheus

20 August, 2007 21:31  
Blogger Another Autism Mom said...

Right. I suppose my father and I are carriers; my sisters, who had NT kids only, may not be. My brother, who hasn't had kids yet, may or may not be a carrier.

Now, in regards to the discussion of causation - if you go to the IAN website, they are emphasizing that this theory supports the argument that an environmental event caused the spontaneous mutation. Parental age is a huge influence, but it can't be the reason for all cases.

In my opinion, whatever this environmental agent may be, it will be very hard to avoid, since autism is pretty much present all over the world no matter how healthy a community is. I think the vaccine theory is crap, and autism parents need to rationally look at data available to see that it will take many years, maybe never, until science figures out what causes that mutation.

21 August, 2007 08:58  
Blogger Prometheus said...

Another Autism Mom,

I'd be a bit cautious about assigning carrier status to any of your family members. Autism is, after all, one of the most rapidly growing diagnoses in pediatric mental health and, as such, has quite a bit of "faddishness".

From what I've seen - and I'm not a psychiatrist or psychologist - children are often labeled as "autistic" based on "educational criteria", which are generally (90+% of the time) much looser and less defined than the medical diagnosis of autism.

Even diagnoses made by a physician are often suspect, as there are a number of less-than-skilled physicians who are happy to slap that label on a child and then start pumping them full of vitamins, supplements, chelators and hyperbaric oxygen.

The thing to remember is that true familial (inherited) autism is the exception. Most of the cases appear to be de novo, meaning that the mutation is present in the child but not in the parents or siblings.

Another critically important point is that these mutations are germ cell mutations. This means that the mutation occurred in the sperm or egg that went on to form the embryo that is now the autistic child. The mutation happened in the parent. It was not due to any exposure that occurred after birth - or even before birth, unless it happened right after fertilization and before the first or second cell division.

If you want to look at possible causes of the mutation, you need look no farther than the air around you. The most common cause of mutations is oxidative damage to the DNA caused by oxygen.

While advanced maternal and paternal age play a role (primarily through accumulating mutations in the germ cell line), almost any other mutagen could be responsible (including the All Time Winner - oxygen!).

If you want to look at environmental exposures, you should be looking, not in the 21st century, but in the late 20th century. And you should look at exposures that the parents received, not the children.


Prometheus

21 August, 2007 09:20  
Blogger Joseph said...

Recently I saw a comment in a blog (I think it was GR's blog) where a parent said something like: "How can it be spontaneous mutations, considering I have 3 autistic children?" Somewhere else another parent said something like this: "How can it be genetic, considering I have one autistic child and one typical child?"

I thought it was funny.

Clearly, autism is often inherited from parents, and often the result of a de novo mutation, and sometimes it could be both. We're probably not talking about a single gene either, but maybe a practically unmappable array of genes. Plus there's no doubt environmental factors that make an autism diagnosis more or less likely.

It's not likely to be something as simple as a predisposing gene with a clear-cut environmental "trigger", such that everyone who has the gene and the trigger is autistic, and everyone how is autistic has the gene and experienced the trigger. Reality is rarely that simple.

21 August, 2007 10:20  

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