In March of 2014, geneticist Dr. Wendy Chung gave a brief TED presentation titled “Autism--What We Know (and What We Don't Know Yet),” discussing the role of genetics in the development of autism spectrum disorder. We know this subject can be a bit technical and dry and you may already be fluffing a pillow for a nice nap after this article, but we will try to keep this informative, interesting, and concise. Genetics does play a large and important role in the development of the disorder and is an important subject to discuss. However, genes are not sole factor that causes the development of autism spectrum disorder. Recent research indicates that genetics and environmental factors are equally influential at causing the onset of autism.1 Science is still not able to answer the “why” of autism, but clues found in our genetics reveal why some individuals are more susceptible to the disorder than others and why individuals experience varying levels of severity. This article will focus on some of the major topics of Dr. Chung’s presentation including: concordance rate amongst siblings, de novo mutations, autism biomarkers and the measures one can take to improve the current state of research within the autism community.
Researchers first identified that genetics play a role in autism in 1977 when Folstein and Rutter conducted the first autism twin study and found that there is a higher probability of identical twins that have autism than there is for fraternal twins.2 This finding was significant because identical twins essentially have cloned DNA but only 4 sets out of 11 identical twins shared a diagnosis, while the other sets of twins had one member on the autism spectrum and one who only showed symptoms of the disorder.2 The researchers also concluded that the “genetic influence on autism is not due to just one gene – a single gene effect would have yielded greater sibling concordance. The possibility that genetic influence on autism may be due to many genes of small effect size could explain why progress has been slow in identifying culprits.”2 As Dr. Chung explains in her presentation, the current estimated concordance rate, or the likelihood of autism being diagnosed in each individual, for identical twins is 77%, for fraternal twins the number drops to 31%, and is approximately 20% for non-twin siblings.3 The phenomenon of identical twins not sharing an autism diagnosis 100% of the time despite having the same DNA indicates that genes do not account for the entirety of autism risk and that environmental factors must play a role.3
Dr. Chung goes on to discuss how genetics play a role in the development of autism and why some individuals can develop the disorder without inheriting any autism risk genes. According to the presentation, genetics play a larger role in autism than other conditions like cancer, heart disease, and diabetes.3 Individuals with autism can have a strong genetic component stemming from one powerful gene or their autism can be the result of a combination of genes in part with the developmental process influencing the development of autism.3 Unfortunately, we cannot simply look at an individual to determine which of these instances led to the development of their autism. When a genetic mutation arises spontaneously in the individual and is not present in either parent then it is what’s known as a de novo mutation. According to Dr. Chung, researchers at the Simons Foundation set out to identify the genes that cause autism by observing comprehensive genetic information to determine the differences between the mother, the father, and the child for 2,600 families. The findings indicate an autism diagnosis could be linked to a single powerful genetic in 25 percent of the individuals within those families.3 However, this leaves 75 percent of cases with unknown causes. During the course of the study, the researchers were humbled by the amount of different genes linked to autism, which number in the 200 to 400 range.3 Fortunately, as Dr. Chung states “there is some method to the madness,” as the genes are not sporadically randomized, but fit together in a network.3 The researchers within this study found that a single, minute mutation in one of our genes can have profound effects on how our brain functions and on our behavior.3 While researchers are still scratching the surface, they are starting to see an emergence of the connection between genes, proteins, molecules and how they interact together to make neurons work, which in turn interact with one another to make circuits work, and how they then work together to control behavior in both individuals with autism as well individuals who have typical cognition.3 SFARI Gene, an evolving database for the autism research community centered on genes implicated in autism susceptibility, currently lists more than 284 genes implicated in autism.5 The amount of combinations of gene mutations that can occur to cause autism is one of the reasons why there is such a variety of symptoms an individual can have on the autism spectrum.
In addition to emphasizing the role of genetics in autism, Dr. Chung stresses the importance of early identification and intervention in individuals on the autism spectrum. It is nearly universally accepted by clinicians in the autism community that early intervention is the best way to quell the symptoms of autism, and when it comes to treatment, the earlier the better. Research in 2012 utilizing the Early Start Denver Model demonstrated that autism treatments can be implemented at an early enough age to potentially physically alter brain development to a “more positive developmental trajectory.”6 Unfortunately, the children involved in this study were between the ages of 18 and 24 months, while the average age of autism diagnosis remains around the age of four, according to the CDC.6-7 Experts believe an accurate autism diagnosis can be made in children from 12 to 18 months, but, in the absence of a medical test, a reliable diagnosis can only be made through a behavioral assessment.8 The two most accepted autism diagnostic tools, the Autism Diagnostic InterviewTM, Revised (ADITM-R) and the Autism Diagnostic Observetion ScheduleTM (ADOSTM), are designed to assess children aged 2 and older.9 Fortunately, researchers are working to detect biomarkers, which in layman’s terms are a distinct characteristic that is an indicator of a particular disorder, for autism. Potential biomarkers for autism could include unique brain activity or poor eye contact. In fact, Dr. Chung illustrates in her presentation how a recent study utilized eye-tracking software to determine infants’ ability to maintain eye contact.3 If clinicians are able to identify a lack of eye contact as a “red flag” for autism or any other biomarker that would provide a clue to autism developing in its early stages, then they may be able to impact the trajectory of the disorder toward a more positive outcome through immediate intervention.
Dr. Wendy Chung concludes her presentation by alluding to the fact that autism research has come very far since the days when autism was still thought to be caused by bad parenting, but also stresses there is so much more to investigate regarding the disorder. To that end, Dr. Chung implores her listeners to join the Interactive Autism Network community as a means of improving research, services, and the overall well-being of individuals and families affected by autism. The IAN community allows families to enroll and participate in autism research through simple questionnaires and to read about the latest advances in autism-related research. The goal of the IAN community is to ensure that families across the country understand the research process and have the ability to influence the direction of that research. Your participation in the community could help lead to treatment breakthroughs, the discovery of important autism biomarkers, and revolutionary advances in our understanding autism’s genetic and environmental components.
The presentation by Dr. Wendy Chung illustrates how genetics play a role in autism in such a way that it is both entertaining to watch and simple to understand, and we recommend taking 15 minutes to watch it. By focusing on sibling concordance rate, autism-risk genes, and early intervention, the demonstration encompasses the mainstays of how genetics relate to autism. The hope is that one day a medical test, perhaps a genetic test, can detect autism at (or even before) birth so that intervention can begin immediately. As Dr. Catherine Lord, founding director for the Center for Autism and Developing Brain in New York, suggests in 2012 article that “in young children—especially under 2-and-a-half years—we shouldn’t treat [autism] as a lifetime disorder. We can offer parents hope that a very young child will move out of the autism spectrum or improve.”9 By studying genetics, researchers hope to unlock some of the mysteries of autism, which can potentially lead to faster diagnosis, better treatments, and even prevention.
1. King's College London. "Environmental factors as important as genes in understanding autism." ScienceDaily. May 4, 2014. Accessed May 15, 2014 www.sciencedaily.com/releases/2014/05/140504095619.htm.
2. Ronald, Angelica, and Robert Plomin. “1977 Paper on First Autism Twin Study.” SFARI: Simons Foundation Autism Research Initiative. March 19, 2008. Accessed May 15, 2014. https://sfari.org/ne...d-robert-plomin.
3. Chung, Wendy. “Autism – What We Know (and What We Don’t Know Yet).” TED Conference, Vancouver, BC. March 2014. Accessed May 15, 2014. http://www.ted.com/t..._don_t_know_yet.
4. Wright, Jessica. “Genetics: De Novo Mutation Rate Higher in Autism.” Simons Foundation Autism Research Initiative (SFARI). September 30, 2010. Accessed May 15, 2014. http://sfari.org/new...igher-in-autism.
5. “SFARI Gene.” Simons Foundation Autism Research Initiative (SFARI). Accessed May 15, 2014. http://sfari.org/resources/sfari-gene.
6. “Early Intervention Improves Social Skills and Brain Activity in Preschoolers with Autism, Study Finds.” Autism Speaks, Inc. October 26, 2012. Accessed May 15, 2014. http://www.autismspe...activity-autism.
7. “Data & Statistics.” Centers for Disease Control and Prevention (CDC). March 24, 2014. Accessed May 15, 2014. http://www.cdc.gov/n...utism/data.html.
8. “How is Autism Diagnosed?” Autism Speaks, Inc. Accessed May 15, 2014. http://www.autismspe...utism/diagnosis.
9. Glicksman, Eve. “Catching Autism Earlier.” Monitor on Psychology 43, no. 9 (October 2012): 56. Accessed May 15, 2014. http://www.apa.org/m.../10/autism.aspx.