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alphacent
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29 Mar 2008, 12:12 pm

I have seen several scientific articles linking the presence of short alleles of the 5-HTT serotonin transporter gene to anxiety disorders such as depression, paranoia, SAD, as well as to autism (and AS). I am wondering if anyone knows of any molecular biologists who are actually testing people for these "short alleles." Certainly in today's world of modern medicine, such a test should be possible.
There are other genes, as well, that supposedly make one more susceptible to having AS. Are any researchers actually testing Aspies for this gene?



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29 Mar 2008, 12:56 pm

alphacent wrote:
I have seen several scientific articles linking the presence of short alleles of the 5-HTT serotonin transporter gene to anxiety disorders such as depression, paranoia, SAD, as well as to autism (and AS). I am wondering if anyone knows of any molecular biologists who are actually testing people for these "short alleles." Certainly in today's world of modern medicine, such a test should be possible.
There are other genes, as well, that supposedly make one more susceptible to having AS. Are any researchers actually testing Aspies for this gene?


McGill University is testing all sorts of stuff. I know they are using MRIs and are making some interesting breakthroughs worth checking out, but I don't think they have anything concrete yet.



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29 Mar 2008, 1:04 pm

Researchers have been uncovering a bewildering array of genetic links to various neurological disorders, including schizophrenia, paranoia, OCD, Parkinson's, depression, and yes, ASD. Not all links are present in all individuals - but those links discovered don't seem to be present in those without the abnormalities.

To demonstrate the difficulty of pinpointing the links, the most common mutation linked to ASD, 16pw11 (IIRC), is found in just over one percent of the subjects thus far tested. (Oddly, the available database of human genotypes includes most of the population of Iceland, as the Icelandic government seems to have requested their entire citizenry to submit to DNA sampling and storage at some point.)


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29 Mar 2008, 1:46 pm

There are common screens for gross mistakes like fragile X, but not for idiopathic autism/AS.
As Deaconblues says, autism genetics are tricky: it is consensus that up to 20 genes, in different combinations in different individuals, lead to higher autism susceptibility. Even this does not equate autism, just much much higher predisposition!

A new approach is that epigentic mechanisms are involved.

I would love to get myself and children "tested" mainly for the fun of it! I like genetics... It would be possible, I guess, but expensive!



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29 Mar 2008, 2:08 pm

katrine wrote:
There are common screens for gross mistakes like fragile X, but not for idiopathic autism/AS.
As Deaconblues says, autism genetics are tricky: it is consensus that up to 20 genes, in different combinations in different individuals, lead to higher autism susceptibility. Even this does not equate autism, just much much higher predisposition!

A new approach is that epigentic mechanisms are involved.

I would love to get myself and children "tested" mainly for the fun of it! I like genetics... It would be possible, I guess, but expensive!


epi whaaat?



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29 Mar 2008, 2:20 pm

Pepperfire wrote:
katrine wrote:
There are common screens for gross mistakes like fragile X, but not for idiopathic autism/AS.
As Deaconblues says, autism genetics are tricky: it is consensus that up to 20 genes, in different combinations in different individuals, lead to higher autism susceptibility. Even this does not equate autism, just much much higher predisposition!

A new approach is that epigentic mechanisms are involved.

I would love to get myself and children "tested" mainly for the fun of it! I like genetics... It would be possible, I guess, but expensive!


epi whaaat?

The way the embryonic structures grow, based on the DNA. It's not always a done deal, apparently. Sometimes, the way a protein folds depends almost as much on chance as on the genetic structure itself (which is why you can have someone who, for instance, carries the encoding for Asperger's Syndrome, without actually expressing it him/herself). With this idea, you could have short chromosomes in pair 16, extra genes in pair 12, and something oddly-formed in pair 7, and depending on exactly how the embryo's brain grows, it may or may not express in that generation - that is, the child may or may not be born with an ASD.

This is as opposed to, for instance, trisomy-21, also referred to as Down's Syndrome - so far as I know, there are no individuals with a third chromosome on the 21st pair who do not express Down's. No epigenetic mechanism is involved, it's pretty much determined from the moment the extra chromosome appears.


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29 Mar 2008, 2:31 pm

DeaconBlues wrote:
Pepperfire wrote:
katrine wrote:
There are common screens for gross mistakes like fragile X, but not for idiopathic autism/AS.
As Deaconblues says, autism genetics are tricky: it is consensus that up to 20 genes, in different combinations in different individuals, lead to higher autism susceptibility. Even this does not equate autism, just much much higher predisposition!

A new approach is that epigentic mechanisms are involved.

I would love to get myself and children "tested" mainly for the fun of it! I like genetics... It would be possible, I guess, but expensive!


epi whaaat?

The way the embryonic structures grow, based on the DNA. It's not always a done deal, apparently. Sometimes, the way a protein folds depends almost as much on chance as on the genetic structure itself (which is why you can have someone who, for instance, carries the encoding for Asperger's Syndrome, without actually expressing it him/herself). With this idea, you could have short chromosomes in pair 16, extra genes in pair 12, and something oddly-formed in pair 7, and depending on exactly how the embryo's brain grows, it may or may not express in that generation - that is, the child may or may not be born with an ASD.

This is as opposed to, for instance, trisomy-21, also referred to as Down's Syndrome - so far as I know, there are no individuals with a third chromosome on the 21st pair who do not express Down's. No epigenetic mechanism is involved, it's pretty much determined from the moment the extra chromosome appears.


I think I get it. Is it epigentic or epigenetic... I seem to see both spellings of it.

If I understand it correctly, a chromosome that is extra automatically manifests whereas one that is just encoded might not and it has something to do with dominance and submissiveness, like blue eyes vs brown eyes. I might be wrong, but I think that's one of the things that they're testing in the Montreal studies.



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29 Mar 2008, 3:32 pm

That's one part of epigenetics. But also
anything, not actually DNA, that effects gene expression: for example mechanisms that activate/deactivate genes, CAN BE PASSED ON TO NEXT GENERATION ALTHOUGH NOT DNA which is something revolutionary and very, very interesting. This means "enviroment" in the very broadest sense (i.e. non-DNA) acts on DNA and these changes do not only effect one generation.

Epigenetic faults could there for be faults that influence gene expression and therfore effect a multitude og genes, which would explain the up to 20 genes associated with autism.



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29 Mar 2008, 3:47 pm

epigenetics refers to changes in gene expression ect without changing the gene sequence ( "on top of" genetics). i think it's one reason why there are no concrete mutations found in all autistics... cause while a mutation on x,y,z gene could result in autism... all you really need is dysregulation of those genes at the epigenetic lvl... which would still result in autism while having no mutations if you screened that person


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29 Mar 2008, 4:04 pm

So, if I understand correctly, there isn't necessarily mutution of genes involved, just that certain genes are expressed a certain way and although they may express this way in one individual, they won't necessarily express the same way in all individuals with the same symptoms?

Am I getting this?



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29 Mar 2008, 4:59 pm

Genetics
The “multigene” model:
It is thought that between 4 and 15 genes are involved in autism
susceptibility Each gene is thought to have a small additive or multiplicative effect, but the actual mode of inheritance is unknown.
Similar autistic phenotypes may arise from different genes or gene combinations, and it has been broadly accepted that this genetic heterogeneity reflects both locus and allelic heterogeneity. This means that autism may be caused by different gene clusters, but also that phenotype may vary quantitatively or qualitatively because of different alleles or allele combinations of the same gene.

Epigenetics:
The epigenetic field studies mechanisms, other than those of the primary DNA sequence, which influence phenotype. Epigenetic modifications include cytosine methylation and post-translational modifications of histones. These modifications can be influenced by exogenous factors, for example mutation, maternal exposures and postnatal experiences.
As approaches to autism genetics have produced such ambiguous results, researches have begun to explore alternative mechanisms that may contribute to autism susceptibility. A growing body of evidence implicates the involvement of epigenetic mechanisms. One circumstance supporting the involvement of epigenetics is that Rett Syndrome and Fragile X Syndrome, which both have phenotypical similarities to ASD, are known to be the result of epigenetic faults, the former by mutation in the methyl-CpG-binding protein which exerts epigenetic regulation by generating repressive chromatin structure, the latter by expansion of a CGG repeat in the FMR1 gene that subjects the gene to epigenetic silencing and loss of expression. Therefore it is hypothesised that a similar mechanism can also be contributing to ASD.
An epigenetic involvement is also compelling because epigenetic modifications produce epialles, (i.e. alleles that affects gene activity, through for example methylation status, but do not change DNA sequence) that cannot be detected using standard genomewide association linkage analysis techniques, and as several linkage peaks identified in these screens overlap regions that are known to be subject to imprinting. One of these areas is 15q11-q13, an area which is associated with autism, but also with Prader-Willi syndrome and Angelman syndrome, which are oppositely effected by genomic imprinting. Interestingly, a subgroup of Prader-Willi and Angelman syndrome patients have autism-like symptoms and it seems that maternal, but not paternal, 15q11-13 duplications confer a high risk of ASD. A greater number of girls with Turner Syndrome, who inherit a maternally derived X chromosome, than girls with a paternally derived X chromosome, develop autism, perhaps because the maternally derived X chromosome has an imprinted area associated with social behavior, which is silenced on the maternal, but not the paternal, chromosome. It is speculated that an epigenetically modified region may explain the over representation of males with autism, a feature not easily explained using conventional genetics.
Some evidence also exists of paternal imprinting on 7q21-22, and maternal imprinting at 7q 32-33 and on chromosome on . A sex limited effect, that may reflect hormone influence, has been suggested: linkage to 7q and 16 p seems to be present in male probands, while linkage to 15q is seen in females.