do all people with ASDs have a fragile x premutation gene?
from what i gather NTs FMR1 gene isn't silenced unlike those with fragile x but then there are others who have a premutation where instead of the CGG repats ranging over 200 they range from 55-200. it would seem that those with autism are in this category but maybe i'm misunderstanding the concept of the FMR1 gene. i'm no genetics expert
Last edited by NullChamber on 28 Jul 2010, 9:06 am, edited 1 time in total.
Didacticity
Yellow-bellied Woodpecker
Joined: 23 Jul 2010
Age: 41
Gender: Male
Posts: 61
Location: Northeastern United States
This is an interesting question.
Based on a quick look at Wikipedia, it seems that Fragile X will result in methylation, but the premutation is not always prevalent to the degree that it will cause methylation. You're positing that the premutation (when it's not severe enough to cause methylation) could be the cause of Asperger's Syndrome. Is this correct?
One of the problems with the theory is that the premutation seems to be associated with poor overall mental acuity, while people with Asperger's have average to above-average intelligence. Also, the physical characteristics of Fragile X don't seem very Aspergian. However, studies providing information about Fragile X and the premutation could be based on individuals with methylation, and as such might not be relevant to individuals with a premutation not severe enough to cause methylation.
Anyway, the above is conjecture, so if SmallFruitSong or anyone else has corrections they're welcome to express them.
Suggestion - please, please don't use Wikipedia.
Best sources on the web: fragileX dot org, fraxa. dot org, pubmed dot gov if you'd like to search research abstracts, pubmedcentral dot gov if you'd like to search full NIH funded studies articles.
As for a peer-reviewed, research supported site I'd use genetests dot org, select gene reviews, and search for FMR1.
Sorry for the "dot"s as a newer member I can't provide URLs.
Fragile X is complicated, like many disorders it is a spectrum disorder, and with Fragile X that exists within the pre-mutation (carrier) range 55-200 CGG repeats and the full-mutation range >200 CGG repeats.
Recent study done by Don Bailey did show that some carriers exhibited various symptoms (one must keep in mind the spectrum, not all will, but there was a greater incidence within the NT population.)
Back to the basic question, do all individuals with Asp. have a premutation of Fragile X, the correct answer is no, not "ALL" but there may be some that do. The only way to know for sure is to be tested, but I'd wait until the new test is available if cost is an issue (from Quest Diagnostics), the FMR1 DNA ranges from $200 to $600 dollars, the new test (which has completed research studies) is as accurate the cost should only be between $5 to $10 dollars.
Just in the news if you want to google it: New York State Approves Quest Diagnostics' Fragile X Syndrome Test
Good luck on finding your answers.
I remember a crazy doctor who thought that without having done any tests, or in fact known me for more than a minute. (Of course, I remember the crazy doctor who wanted to use ether to cure me, too, so I don't put much store by the opinions of crazy doctors. I'm no ret*d.)
_________________
I'm using a non-verbal right now. I wish you could see it. --dyingofpoetry
NOT A DOCTOR
Didacticity
Yellow-bellied Woodpecker
Joined: 23 Jul 2010
Age: 41
Gender: Male
Posts: 61
Location: Northeastern United States
Best sources on the web: fragileX dot org, fraxa. dot org, pubmed dot gov if you'd like to search research abstracts, pubmedcentral dot gov if you'd like to search full NIH funded studies articles.
As for a peer-reviewed, research supported site I'd use genetests dot org, select gene reviews, and search for FMR1.
Sorry for the "dot"s as a newer member I can't provide URLs.
Fragile X is complicated, like many disorders it is a spectrum disorder, and with Fragile X that exists within the pre-mutation (carrier) range 55-200 CGG repeats and the full-mutation range >200 CGG repeats.
Recent study done by Don Bailey did show that some carriers exhibited various symptoms (one must keep in mind the spectrum, not all will, but there was a greater incidence within the NT population.)
Back to the basic question, do all individuals with Asp. have a premutation of Fragile X, the correct answer is no, not "ALL" but there may be some that do. The only way to know for sure is to be tested, but I'd wait until the new test is available if cost is an issue (from Quest Diagnostics), the FMR1 DNA ranges from $200 to $600 dollars, the new test (which has completed research studies) is as accurate the cost should only be between $5 to $10 dollars.
Just in the news if you want to google it: New York State Approves Quest Diagnostics' Fragile X Syndrome Test
Good luck on finding your answers.
Wikipedia has its detractors, but it can be quite useful. It often the most efficient way of investigating topics one doesn't usually deal with, and it's good for catching up with history, literature, and so forth.
It was a little difficult to understand exactly what NullChamber was getting at, but certainly not all people diagnosed with ASDs have Fragile X. However, it begs the question of whether ASDs will be defined in entirely different ways in the future, and the answer to that is likely yes.
He also implied (without directly stating) the question of whether the symptoms associated with Fragile X are caused not by the mutation itself but by the methylation of FMR1. The Southern Blot analysis seems to be (up this this point) the most common test for Fragile X, and it can't discern the number of repeats. This means that it's harder for researchers to study the symptoms of the premutation, and these could be quite distinct from the symptoms of the full mutation. The Quest test sounds exciting since it can determine the number of CGG repeats. Hopefully that will provide some more information in the future.
Didacticity
Very good points!
As for the Southern Blot, it's excellent at identifying full mutations, those with over 200 CGG repeats but may often miss premutations. PCR ananlys which is sometimes done with Southern Blot is excellent at identifying pre-mutations (CGG repeats between 55-200) but may often miss full mutations. This is noted in the practice guidelines for diagnosis of Fragile X estabilished by the American College of Medical Genetics.
The new test by Quest accurately identifies both and will tell us a little more. From conversations I've had with reserchers involved with the study to evaluate the test, this new test also looks at AGG repeats and those AGG repeats are very important in identifying how stable the gene is when the CGG repeats are in the Gray Zone between 45-54 CGG repeats. The AGG repeats, from what they've discovered through research, will identify how stable the gene is, if it is at risk for expansion.
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