Summary: According to a new Nature paper, variation in how children seek social information is under genetic control. Such behaviors are decreases in children with autism, adding further evidence for the link between behavioral presentation in ASD and underlying genetics causes.
Source: Emory Health Sciences.
New study reveals direct genetic influence on way infants see their social world — from how and when they move their eyes to what they look at when watching mom’s face or actions of other children — behaviors also disrupted in children with autism
Researchers at Marcus Autism Center, Children’s Healthcare of Atlanta, Emory University School of Medicine, and Washington University School of Medicine in St. Louis have found striking evidence for the role of genetics in shaping a fundamental feature of human behavior: how children pay attention to the world–what they look at, and what they don’t — is strongly influenced by genetics.
Genetic influence directly affecting how individual infants look at and perceive the world has never before been demonstrated. The results show that variation in how children seek social information — measured across timescales as small as tens of milliseconds — is under genetic control. In addition, these same behaviors were found to be decreased in children affected by autism, providing an important new link between autism’s behavioral presentation and its underlying genetic causes. The results are reported in the July 12, 2017, advanced online publication of the journal Nature.
The study examined 338 children, first tested when they were just 18-24 months old. Eighty-two of the children were identical twins — that is, twins who share the same exact genotype — and another 84 were non-identical twins (twins who share only 50% of their genotype, like other non-twin siblings). The remaining children were either non-sibling controls (84) or children diagnosed with autism (88). During testing, the researchers used eye-tracking technology to measure every movement of each child’s eyes while watching videos of commonly experienced childhood scenes, such as children at play or actresses playing the role of a caregiver.
Each twin was tested independently, at different times, without the other twin present. Nevertheless, identical twins were also nearly identical in the way they watched the videos: how much one identical twin looked at another person’s eyes was almost perfectly matched by his or her co-twin. In contrast, for non-identical twins, that match fell to just about 10%. Identical twins were also much more likely to move their eyes at the same moments in time, in the same directions, towards the same locations and the same content, mirroring one another’s behavior to within as little as 17 milliseconds.
“These data show us that a child’s genes shape the way she sees the world. And how a child looks at the world is how she learns about the world. Each eye movement — happening every half-second–shapes brain development. So you can imagine these effects rippling forward, creating the way a child sees and understands her world,” says Warren Jones, PhD, the study’s senior author and Nien Distinguished Chair in Autism at Emory University School of Medicine. “This changes our understanding of how children experience their environment, and changes our understanding of what forces shape that experience. This shows us that our genetic biology exerts a strong and pervasive influence on what we would otherwise imagine to be unique individual perceptions.”
The effects persisted as the children grew. When the twins were tested again, more than a year later, the same effects were found: identical twins remained almost perfectly matched in their levels of looking, but non-identical twins became even slightly more different than before. “Not only is this aspect of social visual engagement under stringent genetic control,” said John N. Constantino, MD, the study’s lead author and Blanche F. Ittelson Professor of Psychiatry and Pediatrics at Washington University, “but the trait is very stable. Taken as a whole, this means we have a new way to trace direct effects of genetic factors on early social development. This is a mechanism by which genes actually modify a child’s life experience. And, because of that, this creates a new opportunity to design interventions to ensure that children at risk for autism acquire the kind of social environmental inputs that they need.”
Comparison with data collected from children with autism was a critical feature of the study: levels of eye- and mouth-looking–the same traits that showed the greatest degree of genetic influence in typically-developing children–were substantially reduced in children with autism. In autism, the levels were low enough, and different enough, that they could be used to mathematically identify the vast majority of children who did or did not have autism.
“This is an extremely important step,” said Jones. “It’s a link between the behavioral presentation of autism and an objective, quantifiable trait, one that emerges very early in infancy, and one that we now know–with these results–is directly influenced by genetics. How a child looks at the surrounding world, with or without autism, is directly traceable to her genetics.”
Autism is known to be primarily caused by genetic factors, and earlier research by members of the team showed that babies who look progressively less at people’s eyes, beginning as early as 2-6 months of age, are more likely to have autism. Now, with these new results in twins, the team has found a specific behavior that is highly influenced by genetics and directly linked to autism risk.
“Studies like this one break new ground in our understanding of autism spectrum disorder: establishing a direct connection between the behavioral symptoms of autism and underlying genetic factors is a critical step on the path to new treatments,” says Lisa Gilotty, chief of the Research Program on Autism Spectrum Disorders at the National Institute of Mental Health, one of the agencies that supported the study.
Funding: Additional support was given by National Institutes of Health grants HD068479 and U54 HD087011 (Intellectual and Developmental Disabilities Research Center at Washington University) to Dr. Constantino, and MH100029 to Dr. Jones and Dr. Ami Klin at Emory University School of Medicine and the Marcus Autism Center, Children’s Healthcare of Atlanta.
Source: Holly Korschun – Emory Health Sciences
Image Source: NeuroscienceNews.com image is in the public domain.
Original Research: Abstract for “Infant viewing of social scenes is under genetic control and is atypical in autism” by John N. Constantino, Stefanie Kennon-McGill, Claire Weichselbaum, Natasha Marrus, Alyzeh Haider, Anne L. Glowinski, Scott Gillespie, Cheryl Klaiman, Ami Klin & Warren Jones in Nature. Published online July 12 2017 doi:10.1038/nature22999
Infant viewing of social scenes is under genetic control and is atypical in autism
Long before infants reach, crawl or walk, they explore the world by looking: they look to learn and to engage, giving preferential attention to social stimuli, including faces, face-like stimuli and biological motion. This capacity—social visual engagement—shapes typical infant development from birth and is pathognomonically impaired in children affected by autism. Here we show that variation in viewing of social scenes, including levels of preferential attention and the timing, direction and targeting of individual eye movements, is strongly influenced by genetic factors, with effects directly traceable to the active seeking of social information. In a series of eye-tracking experiments conducted with 338 toddlers, including 166 epidemiologically ascertained twins (enrolled by representative sampling from the general population), 88 non-twins with autism and 84 singleton controls, we find high monozygotic twin–twin concordance (0.91) and relatively low dizygotic concordance (0.35). Moreover, the characteristics that are the most highly heritable, preferential attention to eye and mouth regions of the face, are also those that are differentially decreased in children with autism (χ2 = 64.03, P < 0.0001). These results implicate social visual engagement as a neurodevelopmental endophenotype not only for autism, but also for population-wide variation in social-information seeking8. In addition, these results reveal a means of human biological niche construction, with phenotypic differences emerging from the interaction of individual genotypes with early life experience.
“Infant viewing of social scenes is under genetic control and is atypical in autism” by John N. Constantino, Stefanie Kennon-McGill, Claire Weichselbaum, Natasha Marrus, Alyzeh Haider, Anne L. Glowinski, Scott Gillespie, Cheryl Klaiman, Ami Klin & Warren Jones in Nature. Published online July 12 2017 doi:10.1038/nature22999