If you’ve been following autism research in recent years, you have probably read—many times—that familial, or inherited, risk is seldom the whole picture. A few inherited genes are sufficient by themselves to cause autism. But most so-called “autism genes” only increase the risk that an infant will go on to develop this developmental disorder. As is the case in many complex diseases, it appears that autism often results from a combination of genetic susceptibility and environmental triggers.
This is where epigenetics comes in. Epigenetics is the study of the factors that control gene expression, and this control is mediated by chemicals that surround a gene’s DNA. Environmental epigenetics looks at how outside influences modify these epigenetic chemicals, or “markers,” and so affect genetic activity.
It is important to remember that scientists use the term “environment” to refer to much more than pollutants and other chemical exposures. Researchers use this term to refer to pretty much any influence beyond genetic mutation. Parental age at time of conception, for example, is an environmental influence associated with increased risk of autism, as are birth complications that involve oxygen deprivation to an infant’s brain.
Because epigenetics gives us a way to look at the interaction between genes and environment, it holds great potential for identifying ways to prevent or reduce the risk of autism. It may also help us develop medicines and other interventions that can target disabling symptoms. We have written about epigenetics previously on this blog (here and here). So in this answer, I’d like to focus on the progress reported at a recent meeting hosted by Autism Speaks.
The Environmental Epigenetics of Autism Spectrum Disorders symposium, held in Washington, D.C. on Dec. 8, was the first of its kind. The meeting brought together more than 30 leaders in autism neurobiology, genetics and epidemiology with investigators in the epigenetics of other complex disorders to promote cross-disciplinary collaborations and identify opportunities for future studies.
Rob Waterland, of Baylor College of Medicine in Texas, described epidemiological studies and animal research that suggested how maternal nutrition during pregnancy can affect epigenetic markers in the brain cells of offspring.
Julie Herbstman, of Columbia University, described research that associated epigenetic changes in umbilical cord blood with a mother’s exposure to air pollutants known as polycyclic aromatic hydrocarbons (PAHs). PAHs are already infamous for their association with cancer and heart disease.
Rosanna Weksberg, of the Hospital for Sick Kids in Toronto, discussed findings that suggest how assisted reproductive technology may lead to changes in epigenetically regulated gene expression. This was of particular interest because assisted reproduction has been associated with ASD. Taking this one step further, Michael Skinner, of Washington State University, discussed “transgenerational epigenetic disease” and described research suggesting that exposures during pregnancy produce epigenetic changes that are then inherited through subsequent generations.
Arthur Beaudet, of Baylor College of Medicine, discussed a gene mutation that controls availability of the amino acid carnitine. This genetic mutation has been found to be more prevalent among children with ASD than among non-affected children, suggesting that it might be related to some subtypes of autism. Further study is needed to follow up on the suggestion that dietary supplementation of carnitine might help individuals with ASD who have this mutation. Caution is needed, however. As Laura Schaevitz, of Tufts University in Massachusetts, pointed out, studies with animal models of autism suggest that dietary supplementation may produce only temporary improvements in symptoms of neurodevelopmental disorders.
So what does this all mean for research that aims to help those currently struggling with autism? The meeting participants agreed that the role of epigenetics in ASD holds great promise but remains understudied and insufficiently understood. For clearer answers, they called for more research examining epigenetic changes in brain tissues. This type of research depends on bequeathed postmortem brain tissue, and Autism Speaks Autism Tissue Program is one of the field’s most important repositories. (Find more information on becoming an ATP family here).
The field also needs large epidemiological studies looking at epigenetic markers in blood samples taken over the course of a lifetime. One such study is the Early Autism Risk Longitudinal Investigation (EARLI). More information on participating in EARLI can be found here.
Autism Speaks remains committed to supporting and guiding environmental epigenetics as a highly important area of research. We look forward to reporting further results in the coming year and years.
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Read more autism research news and perspective on the science page.
To date, relatively few scientists are studying autism in China. Clearly the need there is great, for with its population of over a billion, we may be looking at millions of persons affected by autism. With this in mind, Autism Speaks partnered with China’s Fudan University to convene a meeting of leading international experts in autism and children’s health in Shanghai last week.
As part of this visit, I and development psychologist Alice Kau, Ph.D., of the National Institute for Child Health & Human Development, visited Xin Hua Hospital and its recently completed Shanghai Key Lab of Children’s Environmental Health. Both are affiliated Shanghai’s Jiao Tong University School of Medicine.
There we met the lab’s executive director, Jun Jim Zhang, MD, Ph.D., and his colleagues. In recent years, they have been studying how exposure to heavy metals such as mercury and lead affects child development. Environmental lead contamination, a problem largely minimized in the United States, remains a widespread problem in China, owing to unsafe disposal of lead products including waste from lead battery plants.
The Shanghai Key Lab’s affiliation with Xin Hua Hospital allows its scientists to collect blood samples at birth and throughout a child’s development. Their lab is also collecting information on intellectual function and other developmental behaviors. Among their projects is the Shanghai Birth Cohort, which will recruit 100,000 pregnant women from hospitals throughout Shanghai and follow their children throughout adolescence.
To date, the researchers at Shanghai’s Key Lab have been focusing their research on potential environmental causes of childhood asthma, sleep disorders and leukemia. Looking forward, they are keenly interested in expanding their research to include neurodevelopmental issues such as autism.
Thanks to our new collaboration, they will be participating in Autism Speaks Environmental Epidemiology of Autism Research Network. In doing so, they will be sharing their information with autism researchers in North America and elsewhere, even as they receive guidance on screening for autism spectrum disorder (ASD).
Given the unique physical, chemical and psychosocial environment in China, we believe that this collaboration can greatly advance our understanding of the environmental and genetic risk factors that contribute to the development of ASD. We look forward to working with this wonderful research team to help solve the autism puzzle in China, North America, and around the world.
Today’s question came in response to my last blog post. In it, I explained that when scientists talk about the “environmental factors” that increase the risk of a disorder, they’re referring to pretty much any influence beyond genetics.
In the case of autism, the clearest evidence of environmental influence seems to surround very early events such as conception, pregnancy and birth. Those with the strongest link include parental age at time of conception (both mom and dad), maternal nutrition or illness during pregnancy, and certain birth complications.
The commenter’s question is a great one that scientists are actively exploring. The short answer is that inherited genes (DNA) and environmental factors seem to interact to influence whether an infant goes on to develop autism. So if the commenter’s twins are fraternal (meaning they share about half their DNA), the difference in their genetic makeup might explain why only one developed autism.
But what if the boys are identical twins–meaning they share exactly the same DNA? In this case, something beyond genes likely accounts for the different outcomes. Comparing the rates of autism among identical and fraternal twins provides clues.
In July, researchers used our Autism Genetic Resource Exchange (AGRE) to complete the largest autism twin study to date. They found a 70 percent overlap in autism among identical twins and a 35 percent overlap among fraternal twins. That overlap between fraternal twins is much higher than the estimated 19 percent overlap between different-age siblings.
These numbers tell us that it’s not always genes alone that determine whether a child develops autism. If it were, two identical twins would always share the same outcome, and the rate of a shared autism among fraternal twins would look more like that for different-age siblings. So we conclude that shared environmental influences are also at play.
Although twins share very similar pregnancy and birth environments, those environments aren’t exactly the same. For example, twins can have different positions in the womb or different placentas, and this can affect such environmental influences as blood and oxygen flow. Indeed, twins often have different birth weights, a known risk factor for autism.
It’s important to remember that “environmental” influences such as these don’t cause autism by themselves. Rather, if a child has a genetic predisposition for developing autism, these influences may further increase the risk.
Autism Speaks continues to fund and otherwise support research on both genetic and nongenetic risk factors for autism. EARLI is a network of researchers who follow mothers of children with autism beginning at the start of another pregnancy. IBIS is a study of early brain development in the younger siblings of children with autism. These studies depend on the participation and support of the autism community. Please visit our Participate in Research page to learn more.
Importantly, these studies provide insights into the underlying biology of different types of autism. This in turn becomes a basis for developing ways to treat and possibly prevent autism. As always, the goal of the research we support is to improve the lives of all on the autism spectrum.
And thanks for the question. Please keep them coming.
Research has taught us that there’s no simple explanation for what causes autism. We know that genes play a role, but they aren’t the whole picture. Environment also matters.
However “environment” can be a tricky term, as pediatrician Perri Klass recently noted in her New York Times column. In autism research, we use the word to refer to pretty much any influence beyond inherited genes—not just exposure to pollutants or other toxic chemicals.
In fact, the environmental factors that research most strongly links to autism are influences such as maternal infection during pregnancy (especially rubella), birth complications (especially those involving oxygen deprivation), and parental age at time of conception (dad as well as mom). Parents who wait less than one year between pregnancies may be at a slightly higher risk for having a child with autism. (Conversely, there is strong evidence that mothers who take prenatal vitamins before conceiving reduce the odds that their children will develop autism.)
Clearly, countless fetuses and babies are exposed to “environmental risk factors” such as these without ever developing autism. But if a child is genetically predisposed to autism, it appears that these influences further increase the risk. For this reason, we say that environmental factors increase the risk of autism rather than cause it.
Research has suggested that many other environmental, or nongenetic, factors may increase the risk for autism. But scientists can’t yet say whether these involve direct (versus coincidental) links. Such factors include a pregnant woman’s exposure to certain chemicals such as pesticides and phthalates (commonly found in plastics) or certain drugs such as terbutaline (used to stop premature labor), valproic acid (to control seizures), and some antipsychotics and mood stabilizers. Of course, in the case of medications, any possible increased risk of autism must be balanced against a woman’s medical needs—which can likewise affect the health of her pregnancy and children.
In addition, most environmental factors associated with autism appear to increase risk only slightly and only in combination with other factors such as genetic predisposition. So it is difficult, in most cases, to pinpoint any one environmental influence. For these reasons, Autism Speaks continues to fund research on a wide range of environmental risk factors. Importantly, the more we learn about how these influences affect brain development, the better we can help the children, adults and families who are affected by autism.
Want to learn more about the research Autism Speaks is funding? On our Science Grant Search page, you can browse studies by topic and location. Finally, if you or your child is affected by autism, please consider participating in one of our clinical studies. Thanks, and please keep sending us your questions.
I hope you enjoy our report on Science Department Monthly Highlights, focusing on major scientific advances and new grants funded by Autism Speaks, as well as the science staff’s media appearances and national/international meetings. Given the size and scope of our science department, we aren’t attempting a comprehensive report here. If you are interesting in knowing more about activities such as tissue donations, participation in clinical trials, and our research networks (e.g. Baby Sibs Research Consortium), please contact me and our science communications staff at email@example.com. Enjoy!
Best wishes, Geri
The dog days of August were anything but quiet for the science department. Highlights included the release of the first major report of the Autism Speaks Baby Siblings Research Consortium. The world learned that autism recurs in families at a much higher rate than previously estimated. For perspective and guidance, the national media turned to our director of research for environmental sciences, Alycia Halladay, PhD. Over the course of 24 hours, Alycia made appearances on CNN, MSNBC, and NPR’s “All Things Considered;” was interviewed by reporters for numerous major papers, news services, and magazines; and even found time to answer parents’ questions via live webchat (transcript here)—the first of an ongoing schedule of live chats to be hosted by science department leadership. Geri Dawson, PhD, our chief science officer, wrote a blog that focused on what the new findings mean for parents.
The science department also hosted a two-day Autism and Immunology Think Tank at the New York City office, with some of the nation’s leading thought-leaders in immunology and inflammatory diseases lending fresh insights to aid our planning of research exploring the immune system’s role in autism spectrum disorders. Glenn Rall, PhD, Associate Professor, Fox Chase Cancer Center and member of Autism Speaks’ Scientific Advisory Committee, and Alycia organized and led the meeting which was attended by senior science staff and experts who study the role of the immune system and inflammation in multiple sclerosis, Parkinson’s Disease, Alzheimer’s Disease, Multiple Sclerosis, inflammatory bowel diseases, and brain development.
Here, then, is the science department’s abbreviated rundown of August highlights:
Major scientific publications published this month supported with Autism Speaks funds and resources
* Recurrence Risk for Autism Spectrum Disorders: A Baby Siblings Research Consortium Study. Ozonoff S, Young GS, Carter A, et al. Pediatrics. 2011 Aug 15. [Epub ahead of print]
* Coming closer to describing the variable onset patterns in autism. Dawson G. J Am Acad Child Adolesc Psychiatry. 2011 Aug; 50(8):744-6.
* Mortality in individuals with autism, with and without epilepsy. Pickett J, Xiu E, Tuchman R, Dawson G, Lajonchere C. J Child Neurol. 2011 Aug;26(8):932-9.
Autism Speaks science staff in the national media
* Alycia gave perspective and guidance related to the results of the Baby Siblings study in The New York Times, Associated Press, USA Today, CNN Health, Time, Healthday, Huffington Post and WebMD; and made related appearances on CNN, MSNBC, and NPR’s “All Things Considered.”
* VP of Scientific Affairs Andy Shih was interviewed by the Philadelphia Inquirer, Parents Express and Education Week about Hacking Autism.
* Alycia was interviewed by Fit Pregnancy about studies on prenatal and early post natal risk factors. She was also interviewed by About.com regarding proposed changes in autism-related entries of next year’s much-anticipated DSM-5 (Diagnostic and Statistical Manual of Mental Disorders, fifth edition).
* Andy and Michael Rosanoff, associate director of public health research, were interviewed by Newsweek for a story about the Minnesota Somali prevalence study.
* Geri was interviewed by Parents magazine for a story about early screening and early intervention.
* VP of Translational Research Robert Ring was interviewed by Discover magazine for a story on the use of mice models in autism research.
* Geri was interviewed by the prestigious journal Lancet regarding autism clusters in California.
* Andy was interviewed by CBS 60 Minutes on innovative autism technology.
* Geri and Simon were interviewed by ABC News on the use of avatars in autism treatment.
* Autism Speaks Global Autism Public Health Initiative continued to generate world headlines, including this Wall St Journal interview, around its Conference on Autism Spectrum Disorders and Developmental Disabilities in Bangladesh and South Asia, which resulted in the adoption of the “Dhaka Declaration” presented to the United Nations.
* On August 15th, the science department hosted its first live webchat, with Alycia fielding questions related to the widely covered release of the Baby Siblings Research Consortium’s findings of unexpectedly high rates of autism recurrence in families. Nearly 1,000 live viewers joined the chat and submitted 299 questions and comments. This is the first of an ongoing series of live web chats by senior science staff.
Science leadership at national and international meetings
* Geri, Andy, Rob, Michael, and VP of Scientific Review Anita Miller Sostek attended the treatment grant review meeting in San Francisco, Aug 1-2. 86 applications focusing on developing and evaluating new biomedical and behavioral treatments were reviewed by a panel of scientific experts and stakeholders. Ann Gibbons, executive director, National Capital Area, offered her expertise as a consumer reviewer on the panel.
* Michael attended the World Congress of Epidemiology, in Edinburgh, Scotland, Aug 7-11. This year’s theme was “Changing populations, changing diseases: Epidemiology for Tomorrow’s World,” and the International Clinical Epidemiology Network Team, which Autism Speaks co-funds, presented on an array of research efforts. In addition, Danish researchers presented data on the increased risk for autism in children with low birth weight and other birth-related conditions.
* Geri and Alycia hosted an Autism and Immunology Think Tank, Aug 22-23, in NYC (described above).
*The Autism Treatment Network leadership held its semi-annual planning meeting in the NYC offices Aug 23-24, with Geri, Clara, Rob, Dr. Dan Coury, Medical Director, ATN, Jim Perrin, MD, Director, Clinical Coordinating Center, ATN, and Nancy Jones attending.
* The science department senior leadership and Mark Roithmayr held a strategic planning meeting with members of its scientific advisory committee in the NYC offices, Aug 24. Among the advisors attending this meeting were Joe Coyle, MD, Chair, department of psychiatry, Harvard Medical School, Gary Goldstein, MD, president, Kennedy Krieger Institute, Steve Scherer, PhD, director, Centre for Applied Genomics, University of Toronto, and Roberto Tuchman, MD, associate professor of neurology, Miami Children’s Hospital.
*On Sunday, August 28th, Geri Dawson presented at the Triennial Conference of the Royal Arch Masons, a group that makes a substantial annual donation to support the work of the Toddler Treatment Network.
Last month, a group of California researchers reported an increased risk of autism among babies whose mothers took a certain catergory of antidepressant medications–selective serotonin reuptake inhibitors (SSRIs)—during the first trimester of pregnancy. You may know these drugs by such brand names as Prozac, Effexor, Paxil, and Celexa.
So what do these results mean for pregnant women? First, caution is needed before rushing to judgment. The study was relatively small, and the increase in the risk of autism was modest. So more study is clearly needed to confirm the link and clarify how great a risk, if any, is associated with a mother using this type of antidepressant during pregnancy.
Further caution is needed because the effects of a mother’s anxiety and depression during pregnancy and early infancy are well known. In fact, it’s not clear whether the autism risk associated with taking antidepressants during pregnancy is, in fact, related to the women’s depression rather than the drugs themselves.
For these reason, many doctors have argued that the benefits of SSRIs outweigh concerns about risks that SSRI exposure may pose to a fetus or infant during pregnancy and nursing. Clearly, more research is needed.
Beyond SSRIs, researchers have looked at several other medications to see if their use during pregnancy increases the risk that a baby will go on to develop autism. Among the most thoroughly researched is the anti-seizure medication valproic acid (U.S. brand name Depakote). Studies show that, as a group, children whose mothers take valproic acid during their first trimester of pregnancy are more likely to develop an autism spectrum disorder (ASD) than are children who are not exposed.
Autism Speaks has supported research into how valproic acid might contribute to the development of ASDs. Through the study of donated brain tissue, for example, we have learned that individuals with autism share some “neuropathologies,” or altered brain features, with those who were exposed to valproic acid before birth. In addition, several studies show that exposure to valproic acid during critical periods of brain development can produce autism-like behaviors in animal models.
So the good news is that our research has deepened understanding about how valproic acid during pregnancy can contribute to the development of ASDs. The bad news is that it can be quite dangerous for women with epilepsy to stop taking this medication during pregnancy—owing to their increased risk of seizures. As a result, such decisions should be made carefully with a physician can discuss alternative drugs.
Findings are still emerging with other medications given during pregnancy. For instance, relatively small studies (such as this one) suggest an increased risk for ASD in babies whose mothers were given the medication terbutaline to stop premature labor. Another small study suggested increased risk of autism related to women taking high doses of the anti-ulcer drug misoprostol early in pregnancy. (This drug is also used to induce labor later in pregnancy.) But in many cases, such preliminary research has yet to move past the “interesting” stage to reach enough certainty to change medical practices.
Other, larger studies hint at an increased risk of autism in the babies of women who take certain broad classes of medications such as antipsychotics or mood stabilizers during pregnancy. Still the question remains: Is the autism risk due to the medications or to the underlying medical conditions that the drugs are being used to treat?
Beyond medications, studies have revealed a number of other pregnancy complications and events that appear to contribute to the risk that a baby will go on to develop autism. These include the pregnant mother’s exposure to toxic chemicals, infections such as flu, and her diet and nutrition at the time of conception as well as during pregnancy.
Autism Speaks continues to fund a number of important studies looking at autism risk factors during pregnancy. If you have at least one child already diagnosed with an ASD, find out more about participating in the EARLI study (link at left) before or at the start of your next pregnancy. Or consider enrolling your child and family in the CHARGE study, which looks at risk factors before, during, and after your child’s birth.
We will be continuing to update you on the science as it emerges. If you have any concerns about the medications you are taking during pregnancy, please discuss them with your doctor. For more resources, we also recommend the Organization of Teratology Information Specialists.
Autism’s recurrence within families is of tremendous interest to both researchers and families, and our “High Risk Baby Siblings Research Consortium” continues to study this and other important questions regarding the risks, causes, prevention, and early treatment of autism.
We support this research consortium in collaboration with the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD). In 2003, Alice Kau, of NICHD, and our own VP of Scientific Affairs Andy Shih organized the consortium. I joined with a leadership role in 2005. Since then, the group has grown to include 25 leading autism researchers across 21 medical centers in the United States, Canada, Israel, and the United Kingdom.
They all share the goal of studying the earliest symptoms of autism spectrum disorders (ASDs). They are able to do so because of the generous participation of families with infants and at least one older child on the autism spectrum. These families are so important to research because of the relatively high likelihood that autism will recur among younger siblings.
By following the development of these young children, our consortium researchers are able to do much more than give us more accurate information on recurrence rates. For example, they are making exciting progress in increasing understanding of how and when autism signs and symptoms first appear. This includes insights into the pattern we call “regression,” which involves a loss of skills in an infant or toddler who appeared to be developing normally. As a group, the consortium has published a number of articles to help guide pediatricians and other primary care doctors in how to approach children and families already affected by autism. Their research into early signs and symptoms, for example, has helped clinicians diagnose and provide treatment as early as 12 months of age.
Several of the Baby Sibling Consortium researchers also participate in another important Autism Speaks group, the Toddler Treatment Network. It has a deeper focus on early signs and symptoms, particularly as they relate to developing earlier interventions that may actually prevent the development of some or all autism symptoms.
Families with recurrent autism are crucially needed to help our researchers identify the genes and other influences that increase the risk that children will develop autism. By allowing our researchers to track progress beginning in pregnancy, for example, families provide insights into such risk factors as parental age at conception, and maternal infection and nutrition during pregnancy.
Our researchers are also tracking brain development and identifying so-called biomarkers (such as distinctive brainwave patterns) for earlier and more accurate diagnosis. And, yes, this research can also help us look at whether certain patterns of vaccination make any difference in the risk of autism among children genetically predisposed to the disorder.
Taken together, a better understanding of early signs and symptoms has led to earlier, better accurate diagnoses of ASD along with important knowledge of what causes autism. This research is not possible without the group working together, and without the valuable support of the National Institutes of Health, and most importantly, the families who donate their valuable time to this research.
Interested in learning more—and perhaps participating in the research? Please check out our list of Baby Sibling Research Consortium researchers and contact one in your area.