Home > Science > Meeting highlights environmental influences on genetic risk factors for ASD

Meeting highlights environmental influences on genetic risk factors for ASD

Everyone knows that some environmental factors can have adverse effects on health, especially early in development.  For example, we know that exposure to cigarette smoke is particularly bad for infants and young children, increasing risk for Sudden Infant Death syndrome, respiratory challenges and middle ear infections.  While we are still learning what kinds of environmental factors might impact the intricate process of brain development, and exactly how these impacts occur, we all want to know how environmental factors influence risk for autism.

Last week the Society of Toxicology met in Washington D.C. to discuss not only environmental effects, but how they may interact with our genes to confer autism risk.  The most popular topic of  this 50th anniversary meeting was epigenetics —literally changes made “above the genome”.   Different epigenetic changes have the effect of making the genetic code more or less available for reading and the production of  proteins.  In other words, the environment can actually turn off the functions of genes, resulting in downstream effects on brain and behavioral development.

During a special symposium organized by autism researcher Isaac Pessah, PhD from the University of California at Davis and Cindy Lawler, PhD at the National Institute of Environmental Health Science, , scientists discussed new data and examples of how environmental factors can lead to changes in autism risk.  Animal models of autism are essential for carrying out tests such as these, as different amounts of exposure to a particular substance can be carefully delivered and the outcomes observed with all other variables controlled.

Janine LaSalle, PhD at the University of California at Davis studied the effects of a flame retardant on behavioral development and cognitive function.  She and her colleagues showed that these cognitive effects, which are similar to those found in autism, are dependent on both the sex of the animal and proper function of epigenetic mechanisms that turn a collection of other genes “on” or “off”.

Researchers in the Tanguay lab at Oregon State University are using the humble zebrafish to study a newly discovered type of gene expression.  The research team is studying the effects of alcohol (ethyl alcohol, both the type found in beverages and and as a biofuel additive to gasoline) and a common acne treatment ingredient (retinoic acid, a metabolite of vitamin A ) on gene expression in the zebrafish.  They are finding that disruptions in this new type of gene expression (microRNAs) can have surprisingly large effects on the rest of the genome.

We know from many previous studies that duplications or deletions of collections of genes—called copy number variants or CNVs—can be associated with increased autism risk.  Scott Selleck, PhD, from Penn State University reported on his study which looked at the genetic background of children in the CHARGE study at UC Davis (http://beincharge.ucdavis.edu/).  Individuals with ASD showed increased lengths of CNVs at certain points in the genome. His lab reasons that these CNVs may be areas of what he calls “genomic instability” where environmental chemicals affect gene expression.   We need to know more about these CNVs and whether or not they are the reason some individuals are more susceptible to environmental factors in development.

Genes and environment interact, yes, but another important factor is when.  Timing of the environmental insult can be crucial.  Studies of neural stem cells are showing us that there exist critical periods in the development of these immature brain cells that include times in which cells divide, and also a later time when the immature cells become either neurons or another type of brain cell known as glia.  It is at these times when environmental influences might have their biggest effect.

Pat Levitt, Ph.D. from the University of Southern California spoke on how the combination of genetic vulnerabilities and  environmental factors can converge to disrupt brain development and function.  One example involves the MET gene, which controls the development of a special class of inhibitory neurons. Previous research showed mutations in MET to be associated with autism, especially in individuals with gastrointestinal dysfunction.

Dr. Levitt and his colleagues demonstrated that exposure to chemicals in diesel fuel exhaust also decreases proper expression of the MET protein.  This reduction in expression leads to changes in complexity and length of neurons as they reach to connect with other neurons.  These changes may contribute to the previously observed effects on brain development.  Interestingly, a recent report notes an increased risk for autism in children whose mothers lived within 1000 feet of a major highway during pregnancy.

Autism Speaks is actively supporting a number of research projects investigating the role of epigenetics in autism, including how environmental factors interact with genetic mechanisms to influence behavior.  A primary focus of research invited for submission to Autism Speaks in 2011 is the mechanism of gene/environment interactions, including epigenetics.

To read about all the research Autism Speaks is funding in this area, click here http://www.autismspeaks.org/science/research/initiatives/environmental_factors.php.

Categories: Science Tags: , , ,
  1. March 15, 2011 at 1:59 pm

    I’ve always thought it had a lot to do with the environment. I have two boys with autism.

  2. Marie
    March 15, 2011 at 3:40 pm

    So, when ARE these critical periods in the development of immature brain cells?

  3. Katie Wright
    March 15, 2011 at 6:35 pm

    I wish this had been webcast so all of us could have seen the meeting.

    I think it is always a good thing to discuss ASD’s environmental triggers but so much of this sounds the same. Also how could an ASD environmental science workshop ignore over vaccination and adjuvants as a causative factor? It seems absurd. This is exactly why we need to have stakeholders at these conferences.

    Gens + environment- yes, yes of course but let’s get down to isolating and studying the prime suspects asap. This is not just an academic exercise there are millions of lives in the balance.

    We need not consume ourselves w/a million possibilities- lets move- recommend no more flame retardants in for children clothing- we are taking an insane risk. What about XMRV + kids and parents? How can we prevent adverse vax reactions/ febrile seizures? Let’s study those specific ASD issues now.

    • RAJensen
      March 16, 2011 at 2:03 pm

      Gene Environment interactions are poorly funded and and largely misunderstand. As far the autism-vaccination debate is concerned, two studies published in Feb and June 2007 show how to properly conduct G x E research. In June 2007 it was discovered that two swatches of genes located on chromosome 2 and chromosome 11 was associated with side effects to the adminstration of smallpox vaccines. The adverse effects were rather mild, but the patients were very healthy adults not small children or infants.
      In Feb 2007 a genetic study was published that was titled ‘ Largest ever autism study indentifies two genetic culprits’. The genetic variants were located in regions of chromosome 2 and chromosome 11 the same chromosome regions subsequently adintified as representing risk for mild adverse effects when adminnstered to healthy adult.

      http://www.scientificamerican.com/article.cfm?id=largest-autism-study-finds-two-genes

      http://news.bioscholar.com/2007/06/new-evidence-links-smallpox-vaccination-side-effects-to-genetic-factors.html

  4. Richard Fauth
    March 15, 2011 at 9:47 pm

    This is the type of research that is badly needed. Genetics to identify riskfactors and the environmental insults that can make the vulnerability causitive in our children. Many thanks to the researchers.

  5. Danielle Purificato
    March 16, 2011 at 10:20 am

    I had my sons Genes tested as a part of all the testing done before his diagnosis and they found that Chromosome 15 had an extra piece on it. The tested me and found the same thing. However, I never had any developmental issues at all, so the woman at the lab told me that they think him having this mutation made him susceptible to being affected by the environment. They are still researching and couldn’t give me any more on the subject, but I am very interested in finding out more..

  6. March 16, 2011 at 2:28 pm

    I wholeheartedly agree with Richard. My beautiful son is challenged with autism and I truly believe it is a combination of vulnerability and exposure.
    On the bright side, Autism Speaks published an article just before the holidays – the science connecting Autism with a mitochondrial dysfunction. This caught my attention, as the company I am associated with launched to the market a nutritional supplement that is specific to supporting and rejuvenating our mitochondria. To make a long story short … after checking with the lead scientist for safety and benefits, Colt has been on this supplement for over 100 days now. His world has opened up! He is present, his eye to eye contact is back, he is playing with other children on the playground, he is engaged in back and forth conversation, his tippy toe walking and arm flapping has diminished … the list goes on and on.
    I share this because if it can help my son, I know in my heart it can be a missing piece of the puzzle for another child.
    This past weekend we celebrated Colt’s 9th birthday … both he and his sister enjoyed a pool party with ~ 15 other children. The noise level, the laughter … all so comforting, because Colt was smack in the middle having a GREAT time.
    God Bless.
    Stephanie

    • Pollie
      March 16, 2011 at 8:47 pm

      That is wonderful! So happy to hear he is doing well! I read that article myself. Are they releasing the supplement (or has it been released)?

      • March 20, 2011 at 3:31 am

        Pollie,
        The supplement has been on the market since last Sept / Oct. It is called ageLOC Vitality and is specific for supporting and improving the three dimensions of vitality—physical vigor, mental acuity, and sexual health—by promoting healthy YGC activity associated with youthful vitality … supporting and rejuvenating our mitochondria. The market is for the average person, but the progress my son has made truly has been phenomenal. And the connection I made was because of that article re: Autism and dysfunctional mitochondria. Yes, I am a distributor in the company, but this came about almost a year into my career. Medical claim NO … testimony YES!
        Just sharing our amazing story. Colt has been on the supplement for 103 days today … and our reality has been blessed. Please send me your e-mail and I will share Colt’s journal and more information.
        God Bless.

      • Pollie
        March 20, 2011 at 8:01 am

        Thank you Stephanie, I’m going to start looking into this today. I am very glad it is working for your son.

  7. Sarah
    March 17, 2011 at 5:22 pm

    Stephanie – nice spam.

    • March 20, 2011 at 3:37 am

      Sarah,
      I am sorry you feel this way. No spam … simply sharing our story. My son celebrated his 9th birthday today. Four months ago we would not have been able to have a party as we just did. This is a nutritional supplement that for Colt is a missing piece of his puzzle. We have more than hope …
      God Bless.

  8. Sarah
    March 17, 2011 at 5:24 pm

    Thank you Autism Speaks for this invaluable research into epigenetic research. I agree with Katie – I wish you would have webcast it.

  9. Steven Balogh
    March 18, 2011 at 12:56 pm

    Stephanie-I have a 5 year old boy with autism and I would like to know which company makes this nutritional supplement and what is the supplements name? Please reply as I would be interested in trying this on my son Ben. Thank You & God Bless!

    • March 20, 2011 at 3:41 am

      Steven,
      The supplement is ageLOC Vitality by Nu Skin Enterprises. Please send me your e-mail and I will send you Colt’s journal along with more info.
      God Bless!

  10. March 18, 2011 at 4:20 pm

    I think it’s past time for the scientists to research and discuss what, in my opinion, is the cause of a substantial number cases of Autism. INDOOR MOLD EXPOSURE due to surface and subsurface water entering the building envelope, causing mold growth. It is estimated that twenty five percent of all houses constructed in the last decade or so has water/moisture intrusion leading to excessively high humidity levels creating mold, and making the sick house the perfect enviroment for mold growth. Everyone needs test their home for mold, and spend some time looking at the research being done by Dr. Dorr Dearborn. This doctor has spent decades researching mold exposure and the many illness indoor mold exposure can cause. Also, just google: Mold exposure and Autism!

  11. March 21, 2011 at 4:51 pm

    Pollie :Thank you Stephanie, I’m going to start looking into this today. I am very glad it is working for your son.

    Pollie,

    If you have any questions, please feel free to contact me at: stephsstuff@hotmail.com

  1. January 20, 2012 at 5:37 am

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