New Study on the Genetic Causes of Autism

90 percent of autism may have a genetic basis, geneticist Stephen Scherer of the University of Toronto and the Hospital for Sick Children in Toronto notes in a February 18th Reuters article. A study on the most extensive findings so far on the genetics of autism by Scherer and researchers from a consortium of 19 nations appears today in Nature Genetics. Entitled Mapping autism risk loci using genetic linkage and chromosonal rearrangements, the five-year study suggests that autism has “numerous genetic origins rather than a single or a few primary causes.” DNA samples from 1,168 families—”the largest cohort yet of ASD families yet assembled”—with two or more autistic children were analyzed.

Two new genetic links that may predispose a child for autism were found:

The study incriminated a gene called neurexin 1 involved with glutamate, a brain chemical previously implicated in autism that plays a role in early brain development, as a possible susceptibility gene for autism. A previously unidentified region of chromosome 11 also was implicated.

Neurexins are “a large family of proteins that act as neuronal cell-surface receptors” (Nature Neuroscience 6, 708 – 716 (2003) ); they and neuroligins have been implicated as having a role in autism. The Nature Genetics study pinpoints neurexin-neuroligin link as “fundamentally important for glutamatergic synaptogenesis and thereby points to “glutamate-related genes as promising candidates for contributing to ASDs.” (Glutamate is a common excitatory neurotransmitter in the central nervous system and plays a crucial role in both memory formation and information processing; “synaptogenesis” refers to the formation of synapses.)

We now have “a pretty decent understanding of what the genetic architecture is looking like in the autism genome,” as Scherer was quoted as saying. Scientists hope that, by figuring out the genetics of autism, they can figure out better ways to diganose it and also develop drugs to treat autism.

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    • http://whitterer-autism.blogspot.com/ mcewen

      Well, let’s watch, wait and listen to see how these facts impact certain persons of a different persuasion.
      Cheers

    • http://compostermom.blogspot.com Daisy

      Interesting. My family wasn’t part of this study — but I have a son with Aspergers and a cousin with autism. It will be itneresting to see how the information is applied.

    • http://www.autismvox.com Kristina Chew, PhD

      Seems more and more likely to me that, had we had a second child, he or she would have been on the spectrum….

    • Susan

      Is the OXTR gene implicated in any of these findings? It seems likely maternal oxytocin levels are somehow related to autism.

    • http://www.shiningcityvisions.com laurentius-rex

      Looking at it so far more than one group of researchers have located a lot of different “possible” genes, no-one has anything definate and I am not sure if all these teams agree.

      I don’t know who is keeping records of all this but I bet if you put the lot of it together in a chart it is looking very messy and confused with claim, counter claim, and contradiction.

      The idea of anyone claiming that a drug could rectify whatever the gene got wrong is horrendous.

      I do not doubt that you just can’t fix things so simply and there would likely be huge side effects not even thought of. Flowers for Algernon anyone.

    • Julia

      Flowers for Algernon, indeed.

      And just from seeing expression of autistic traits in my kids’ family (i.e., my family and their father’s family), it’s probably awfully complicated.

      Although I’m willing to bet there’s going to be an awful lot of prosopagnosia around here once it can be identified in our kids, whatever else happens….

    • http://www.autismvox.com Kristina Chew, PhD

      This ABC news story compares the autism-causing genes to criminal elements:

      Autism, found in one of about every 160 people around the world, has many degrees and types, and piles of evidence hinting that genes โ€” not one but many genes โ€” are to blame.

      But how to find them? It’s like trying to find a few dozen innocent looking criminals in a crowd of millions.

      Now, scientists have probable cause implicating dozens of prime suspects all corralled in one place โ€” the collection of 23 X-shaped chromosomes that hold our DNA and are found in every cell in the body.

      Not the best metaphor, I think.

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    • Serpent

      Kristina,

      Everyone in the news says this study revealed two NEW genetic links for autism (neurexin 1 & region in chromosome 11) but nobody mentions if it confirmed previously suspected genetic links, and which ones.
      Do you know anything about that?
      Thanks!

    • http://www.autismvox.com Kristina Chew, PhD

      I will consult the article and get back to you—-

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    • RA Jensen

      What is 90% heritable? Autism per se or autism susceptability genes that require an environmental insult, the ‘second hit’ theory? The polygenic theorists have always claimed that autism is 90% heritable based on twin studies, clustering within families and a higher sib risk ratio than is found in the general population.

      It is useful to compare the genetic component of autism to the genetic component of other conditions that are more clearly understood.

      The cause of leprosy, exposure to myobacterium Laprae, has been known for over a hundred years. What is not known is that the magnitude of the genetic component found in leprosy mirrors the genetic data in autism.

      Twin studies in India demonstrate the magnitude of the genetic component in leprosy with high concordance rates reported in MZ twins ( 60 – 85% ) and a rapid falloff in concordance reported in DZ twins ( 5 – 20% ). Leprosy clusters withon families and leprosy multiplex families have recruited and genome wide scans searching for leprosy susceptability genes have been underway for a decade. There are as many candidate genes reported in leprosy susceptability as there are in autism. The sib risk ratio in leprosy is 2.4, the same ratio reported in many autism family linkage studies.

      http://www.nature.com/ng/journal/v27/n4/full/ng0401_439.html

      Ther is also the same unexplained high male to female ratio reporte in leprosy population studies as has been consistently reported in autism research

      http://www.scielosp.org/scielo.php?pid=S0042-96862001000400007&script=sci_arttext

      “Between 1949 and 1998 a total of 474 774 leprosy cases were detected in China; 75.2% were males and 24.8% were females (male:female = 3:1)”

      I don’t question the data in autism genetic research, it is the interpretation of the data that can be questioned

    • Gina

      RE: the Leprosy/Autism discussion. Have any of you investigated the recent work done in Mendelian Susceptibility to Mycobacteria? I personally, think that a combination of this genetic disorder ( which is also a spectrum disorder as the genes can be really badly messed up, medium messed up or only slightly, resulting in different outcomes) combined with encountering mycobacteria in the pre-natal womb enviroment (extra-pulmonary TB is often transmitted in the womb) or afterwards is at the root of what causes Autism. It would explain its increase as mycobacterial infections of all types are on the rise all over the world and it would also provide a NEW insight into the vaccine problem. Apparently, in some populations, like those who may have genetic pre-disposition to Mendelian Mycobacteria Susceptibility, when they get a vaccine, their circulating levels of immune system protecting gamma inteferon drop, either temporarily or sometimes permanently (thus causing the repeated infections that some autistics face again and again), and during this period of deactivated gamma interferon caused by NUMEROUS vaccines, a child who had a appeared to be developing normally, could contract the mycobacteria (other other viruses or mycrobes) and thus the austism would begin to show. You can check out the interferon gamma problem by googling vaccines and gamma interferon disruption.

      Hope this helps,
      Gina

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    • http://www.healingelijah.com Robert C. Parker

      It is time to stand up and face the truth! My son was diagnosed march ’07, I had asked the Nuerologist what causes this, Genes, he said, not mine or my wifes genes, my sons genes? He also stated there are no alternative ways to heal or cure him, we were told to start him in all the therapie$, change the way we parent and move clo$er to the facility where he is, (we live in a rural 20 acre area)…Thank the creator I didn’t stop there, we have since discovered may children being cured through alternative medicines and most important the diet, which brings me back to the “Truth”, my son was injured by his vaccinations, this is what caused his regression, it is time to admit and accept this so we can go forward and start helping peoplee affected by this both physically, and monetarily.
      There is much more to be said and done! I’ll leave it at that for now.

    • http://www.healingelijah.com Robert C. Parker

      It is time to stand up and face the truth! My son was diagnosed march ’07, I had asked the Nuerologist what causes this, Genes, he said, not mine or my wifes genes, my sons genes? He also stated there are no alternative ways to heal or cure him, we were told to start him in all the therapie$, change the way we parent and move clo$er to the facility where he is, (we live in a rural 20 acre area)…Thank the creator I didn’t stop there, we have since discovered many children being cured through alternative medicines and most important the diet, which brings me back to the “Truth”, my son was injured by his vaccinations, this is what caused his regression, it is time to admit and accept this so we can go forward and start helping people affected by this both physically, and monetarily.
      There is much more to be said and done! I’ll leave it at that for now.

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    • t.d

      “It would explain its increase as mycobacterial infections of all types are on the rise all over the world and it would also provide a NEW insight into the vaccine problem”

      could smoking have a protective effect ? it all began rising after this antismoking craze .. if u still can find links have a look if smoking kills mycobacteria .. google for example for smoking and complement activation