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New mutations implicated in half of autism cases
news@nature.com ^ | 24 July 2007 | Heidi Ledford

Posted on 07/25/2007 12:12:34 AM PDT by neverdem

news@nature.com - the best science journalism on the web Close window



Published online: 24 July 2007; | doi:10.1038/news070723-1

New mutations implicated in half of autism cases

Disorder linked to genetic differences between parent and offspring.

Heidi Ledford



Autistic children display a wide range of different symptoms.HENNY ALLIS / SCIENCE PHOTO LIBRARY

Half of all cases of male autism may be caused by spontaneous genetic mutations, say researchers who have studied the genetic patterns of the condition. Offspring who inherit such mutations are at a greater risk of having an autistic child themselves.

Autistic people have difficulty relating socially with others and tend to focus obsessively on a narrow set of interests. Three to six out of every 1,000 people are expected to have the condition; its cause is unknown but there is thought to be a strong genetic component.

"That genetics plays a major role in autism has been obvious now for 20 years or more," says Isabelle Rapin, a neurologist at Albert Einstein College of Medicine in New York, who was not affiliated with the study. "The evidence for genetics is not controversial."

But determining how genes affect autism has been difficult. Autism is a complex disease with a wide range of symptoms and severity. It also affects four times more males than females, for unknown reasons.

Spontaneous mutation

Earlier this year, a genome-wide scan linked some cases of autism with mutations in the number of copies of certain genes. Ten per cent of autistic patients had copy-number mutations that were not present in either parent, showing that the mutations were spontaneous1.

But Michael Wigler, a geneticist at Cold Spring Harbor Laboratory in New York and a lead author on the study, says that the study probably missed some copy-number mutations. "We were sure that 10% was an underestimate," he says.

So Wigler and his colleagues turned to a database containing pedigrees of families with two or more autistic children and asked: if the family's first two children were autistic, what were the chances that the third was autistic as well?

In 86 families with two autistic children and a third, male child, 42 of the third-born children showed autistic symptoms, the researchers report in Proceedings of the National Academies of Sciences2.

This suggests that parents had a one-in-two chance of passing on a mutation to their offspring, matching a dominant inheritance pattern. Another database gave the same result.

Handed down

Using mathematical models, Wigler's team found that the simplest way to describe the patterns of autism inheritance was to divide parents into two risk classes: those who carry a pre-existing autism-causing mutation, and those who do not.

The models suggest that about half of autistic children are born to parents with no previous genetic predisposition to autism, suggesting that the cases are caused by spontaneous mutations.

Older mothers, who are more likely to have autistic children, could fall into this class, notes Wigler. Such mothers' eggs have had more time to accumulate mutations.

Once those spontaneous mutations have been passed on, the offspring — particularly women, who can carry the mutation without showing symptoms — have a high risk of having an autistic child. Males with the mutation would also bear this risk, but are also likely to be autistic and therefore less likely to have children.

The researchers' model suggested that about a quarter of autistic children have inherited a copy-number mutation from their parents.

"It's a new way of looking at the data," says Rapin. Future studies using data from other family members are needed to further test the new models, she says. Other factors, such as complications during pregnancy, and the influence of multiple genes, may also be important in causing autism.

Visit our newsblog to read and post comments about this story.

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References

  1. Sebat, J. et al. Science 316, 445-449 (2007). | Article | PubMed | ISI | ChemPort |
  2. Zhao, X. et al. Proc. Natl Acad. Sci. USA doi: 10.1073/pnas.0705803104 (2007).


TOPICS: Culture/Society; Extended News; News/Current Events
KEYWORDS: autism; cnv; copynumbervariation; copynumbervariations; genetics; godsgravesglyphs; health
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To: randita

Personally I think it is something as simple as the widespread use of plastics in our food supply. I know they are supposed to be bio-inert. But they really are not over time.


21 posted on 07/25/2007 9:26:48 AM PDT by Chickensoup (If it is not permitted, it is prohibited. Only the government can permit....)
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To: bannie
Radiation from the color spectrum of purple emitted and received into the body from sitting too close to the TV watching Barney. That's my guess. But it might be the center of green surrounded by purple. I need more funding to research this.
22 posted on 07/25/2007 9:27:43 AM PDT by CJ Wolf
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To: bannie
What’s tweaking our DNA to mutate?

Icky food and toys from China.

23 posted on 07/25/2007 9:28:54 AM PDT by madison10
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To: neverdem
Ten per cent of autistic patients had copy-number mutations that were not present in either parent, showing that the mutations were spontaneous.

What if 10% of all children have copy-number mutations that are not present in either parent?

24 posted on 07/25/2007 9:40:57 AM PDT by edsheppa
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To: bannie
What’s tweeking our DNA to mutate?

Clearly, in the industrial age, we're exposed to all kinds of chemical compounds that people a couple of centuries ago could never have encountered. Also, things that would formerly kill babies either in utero, or shortly after birth, are being "corrected" for, and the genetic underpinnings of those things are being passed on to the next generation.

25 posted on 07/25/2007 9:48:04 AM PDT by hunter112 (Change will happen when very good men are forced to do very bad things.)
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To: AdmSmith

Thanks for the link.


26 posted on 07/25/2007 10:02:33 AM PDT by neverdem (Call talk radio. We need a Constitutional Amendment for Congressional term limits. Let's Roll!)
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To: Monkey Face

Except when driving... then, everyone falls into three groups — Me, those who are driving too slow, and those who are driving too fast. ;’)


27 posted on 07/25/2007 10:10:46 AM PDT by SunkenCiv (Profile updated Monday, July 23, 2007 https://secure.freerepublic.com/donate/)
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To: SunkenCiv

thanks.

i know an autistic child.


28 posted on 07/25/2007 10:10:59 AM PDT by ken21 ( b 4 fred.)
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To: CholeraJoe

We don’t have to worry about this much longer — cases after January 1, 2010, will be referred to as “teenism”.


29 posted on 07/25/2007 10:12:24 AM PDT by SunkenCiv (Profile updated Monday, July 23, 2007 https://secure.freerepublic.com/donate/)
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To: ken21
i know an autistic child.

I am highly suspicious of my nephew's 4 year old son and the younger sister. I have talked to one of my sister's about the child's behavior and she agrees that there is something wrong. However, she says that when she talks to our other sister about her grandson, she says that the childs mother will not enter into any discussion about it. Its almost as if the mother is in denial that there may be a problem with the son and quite possibly the younger daughter too......

30 posted on 07/25/2007 10:21:28 AM PDT by Hot Tabasco
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To: SunkenCiv

Ohyah...I forgot about that! LOL!


31 posted on 07/25/2007 10:29:01 AM PDT by Monkey Face ("Equal opportunity" means everyone will have a fair chance at being incompetent. ~~ L J Pete)
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To: neverdem

It seems like everyone here on FR thinks Big Pharma can do no wrong, and wants to say that vaccines have nothing to do with autism — but I know several families whose children were perfectly normal, received a vax, and they then watched their normal child regress into autistic behaviors nearly immediately.

When you overstimulate the immune system (i.e. with vaxes) you can’t possibly predict every outcome. I believe some children are just more susceptible.


32 posted on 07/25/2007 10:42:46 AM PDT by Zechariah_8_13 (Courage is not simply one of the virtues, but the form of every virtue at the testing point.)
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To: Hot Tabasco

that’s sad.

this girl is 4 years. she’s the daughter of a friend of mine. my unprofessional opinion is that she’s a “high functioning” autistic child.

when i first met her she was 3. now, she’s picking up language at an accelerated rate.

her autism includes: 1. she doesn’t recognize emotions in other people. for example, if her mother gets angry at another person, she doesn’t see it.

2. she’s very visual. very, very. likes puzzles. draws well.

3. she has no fear of strangers. this requires complete supervision of her.

she likes men. very few men she does not like. most children her age are removed from strangers and men.

she adores her princess videos, dolls, etc. she stares at her princess and mermaid dolls for hours.


33 posted on 07/25/2007 10:43:01 AM PDT by ken21 ( b 4 fred.)
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To: neverdem

What I’m saying:

Genetics loads the gun, but environment pulls the trigger.


34 posted on 07/25/2007 10:54:25 AM PDT by Zechariah_8_13 (Courage is not simply one of the virtues, but the form of every virtue at the testing point.)
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To: Zechariah_8_13; Incorrigible
Genetics loads the gun, but environment pulls the trigger.

That's a common hypothesis. IMHO, this latest stuff implicates copy number variation, and more specifically, IIRC, the deletion of genes in males. I'm not a geneticist, just a physician trying to understand what's going on.

IMHO, I think the increased prevalence of autistic spectrum disorder is due to having more specific diagnostic criteria, i.e. in the past many would have been diagnosed as mentally retarded, in addition to those now diagnosed with pervasive developmental disorder and Asperger's syndrome.

35 posted on 07/25/2007 11:29:27 AM PDT by neverdem (Call talk radio. We need a Constitutional Amendment for Congressional term limits. Let's Roll!)
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To: ken21

My nephew’s son is not loveable like the other kids in the family, does not interact with adults other than his parents,and the most telling of all is he will suddenly stop what he is doing and start shaking his hands until his mom has to go over to him and stop him. I even saw this last Christmas when he was seated at the childrens table for dinner. He stopped eating and started shaking his hands till his mom stopped him and had him refocus on his meal.


36 posted on 07/25/2007 12:25:57 PM PDT by Hot Tabasco
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To: Hot Tabasco

Those are some telltale signs there.

Your sister is doing him no favors by denying that he has Autistic behaviors. The earlier the intervention, the better it will be for him in the long run.


37 posted on 07/25/2007 2:22:40 PM PDT by Incorrigible (If I lead, follow me; If I pause, push me; If I retreat, kill me.)
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To: neverdem
the increased prevalence of autistic spectrum disorder is due to having more specific diagnostic criteria

That's definitely happening and yes, they would would have been classified as mentally retarded in the past.  Also the broadening of the Autism spectrum by Autism advocate organizations (something I don't agree with).

However, there have been studies done that indicate that the rise is not entirely from better diagnosis.

 

38 posted on 07/25/2007 2:25:05 PM PDT by Incorrigible (If I lead, follow me; If I pause, push me; If I retreat, kill me.)
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To: neverdem

Genetics COULD play a part but they really can’t predict it.

A couple we know had one autistic child. They did a genetic work up and saw the odds as astronomical that the next would be autistic. The plan was that the second child would care for the older brother. Well, against all odds, the second son was also autistic.


39 posted on 07/25/2007 2:46:03 PM PDT by nmh (Intelligent people recognize Intelligent Design (God) .)
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To: randita

You’re right.

They really don’t know.

They’d like you to believe they are making progress in udnerstand this but they haven’t made any progress.


40 posted on 07/25/2007 2:47:30 PM PDT by nmh (Intelligent people recognize Intelligent Design (God) .)
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