Wednesday, 29 April 2009

Chromosomes 5,7 and Autism

From Genome Web :
The first common variant associated with autism has been identified and validated, according to a new study scheduled to appear online today in Nature. The paper, one of several autism genetic studies published online this week, supports the idea that autism involves altered connections between neurons or brain cells.

A team of researchers from across the US genotyped more than 10,000 individuals in an attempt to uncover genetic variants and copy number changes linked to autism and autism spectrum disorders. Their search turned up half a dozen common SNPs in a region on chromosome 5 between CDH9 and CDH10, cadherin genes coding for proteins that help glue cells together. One of these reached genome-wide significance and appears to account for roughly 15 percent of the population risk of autism.
An independent study led by University of Miami Institute for Human Genomics Director Margaret Pericak-Vance and published in the Annals of Human Genetics appears to confirm the connection between the CDH9/10 region and autism, suggesting neural cell adhesion plays a role in autism.

"Until now, no common genetic variant has been identified with such overwhelming evidence to support its role in autism spectrum disorders," Pericak-Vance said in a statement. "The identification of a common variant for autism is a monumental achievement. Researchers have been looking for clues about the genetic architecture of autism for decades."
"In most cases, it's likely that each gene contributes a small amount of risk, and interacts with other genes and environmental factors to trigger the onset of disease," Hakonarson said in a statement.
Meanwhile, in another autism genetics paper scheduled to appear in Molecular Psychiatry, a European research team did a high-density association analysis of regions on chromosomes 7 and 2 that were previously implicated in autism by the International Molecular Genetic Study of Autism Consortium in a few hundred families. That work suggests at least two genes on chromosome 7 — IMMP2L and DOCK4 — contribute to autism.
"Environmental factors in the womb causing a pre-disposition caused by several distinct genes to be triggered". Now where have I heard that before? Oh yes, it's our current "best guess" as to what is causal for Transsexuality, and for that matter, why phocomelia is triggered by Thalidomide in some cases and not in others.

Androgen Receptor Repeat Length Polymorphism Associated with Male-to-Female Transsexualism by Hare at al Biological Psychiatry Volume 65, Issue 1, Pages 93-96 (1 January 2009)

A polymorphism of the CYP17 gene related to sex steroid metabolism is associated with female-to-male but not male-to-female transsexualism by Bentz et al Fertility and Sterility , Volume 90 , Issue 1 , Pages 56 - 59

Again, the correlation is subtle, only a 5 or 10% increase in chance. But in the same ballpark.

There is no "autism gene" or "transsexual gene" or "phocomelia gene". There are genes that increase the chances significantly, allowing anomalous environmental factors (such as administration of Thalidomide or DES) to trigger the syndrome. And sometimes, it just happens, with no obvious environmental stimulus. If I was doing the research, I'd start looking for anomalous foetal environmental factors in cases of autism too. I think we have here a "meta-pattern", a pattern that patterns of development of different congenital syndromes follow.


Anonymous said...

Might there be some kind of connection between autism and transsexualism? I have encountered too many people who are somehow connected with both conditions for me to overlook the possible significance of such a relationship.

Anonymous said...

Thankyou very much for posting this. When I first saw the newspaper headlines this morning I went into what I call "Goldacre mode"*, wanting to know the sources etc. I was half expecting another Wakefield! But the 'gene for' line was bad enough.

Nica could please say what you mean by 'somehow connected' as I am puzzled by the term.

* a reference to Ben Goldacre of

MgS said...

I suspect that Nica is referring to anecdotal claims that there is a higher rate of Asperger's syndrome among transsexuals.

Zoe Brain said...

Given that there's a Yahoo! group specifically for the many TS people with ADD, it's rather more than mere anecdote.
But there have been no formal studies I know of on the issue. It's just something we know, like the high incidence of ambidexterity. That's been formally recorded, but only as a side-effect of other studies.

See a previous post that has some relation to the issue.

One thing - there's a correlation between Transexuality and what has been described as "ultra male syndrome" - Asperger's. Might this "ultra-male" grey matter pattern be the cause? And could a change to a female hormone regime cause changes to it?

Patience said...

The overlap between transgenderism and ASDs is one of the things that's got me going back to school to get my premed requirements done so I can apply for med school. I became fascinated with autism as an offshoot of being fascinated with quack medicine, and in the process have landed myself in a psychologist's office (in my mid twenties, mind) getting assessed for Asperger's.

What always struck me about Baron-Cohen's "extreme male brain" hypothesis is that we should be seeing a huge number of queer women and transmen on the spectrum--anectdotally, I know a handful of bisexual and lesbian women who are Aspies, but anectdotes are not data--since the current science on the development of sexuality and gender identity have to do with (among other things) hormonal exposure prenatally, too. One would think we would conversely see very few gay men and transwomen on the spectrum. I'd love to study this, but, then, I'm a bisexual Aspie girl with dreams of med school at the moment.

Anonymous said...

on the other hand the writer sof the 'How babies thinl' book showed that small babies need to engage is a basic form of conversation with a parent'other even though the actual speech is nothing but gurgles and bubble blowing...but the baby gurgles then waits for a response and then gurgles again etc..
now I think thast the modern tendency to stick young babies in front of a non-responsive loud telly which prevents this conversational gurgling might actually cause the brain to shut down and give the effect of not only autism but ADHD too.
in olden days and primitive societies autism is at very ow rates and babies are surrounded with normal speech patterens and are the centre of attention where the gurgling/convo is encouraged or at least facilitated...


l'alchimiste said...


Televisions are not effective parents, no doubt. And of course, one whose actual parents has used the former as the latter are going to suffer developmental problems.

But when people start using conservative ideas about modern technology to erase other people, then I get pissed. Autism is not caused by kids watching TV; it is a real and pervasive condition that has affected thousands of people both now and in the past, regardless of whether people have identified it or chosen to accept it or not. It's like right-wingers in the US going on about homosexuality being caused by liberals, Barney, or the Democratic Party. Too bad it has over two thousand years of documented history, and was afforded far greater tolerance even in Christian societies of the fourth and fifth centuries than it is today.