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Implications for genetic link to autism

Researchers have broken new ground in understanding a cause of autism, with results published in the July 3rd, 2014 edition of Cell magazine. In a collaboration involving 13 institutions around the world, the study, "Disruptive CHD8 Mutations Define a Subtype of Autism in Early Development," indicates that mutation of a specific gene (CHD8) causes some cases of autism.

In the study of 6,176 children with Autism Spectrum Disorder (ASD), researchers found that 15 had a CHD8 mutation., All of these cases had similar characteristics in appearance, issues with sleep disturbance, and gastrointestinal problems.

Raphael Bernier, the lead author, and UW associate professor in the Department of Psychiatry and Behavioral Sciences and the clinical director of the Autism Center at Seattle Children's, said people with a mutation in the CHD8 gene have a very "strong likelihood" that they will have autism marked by gastrointestinal disorders, a larger head and wide set eyes.

We finally got a clear cut case of an autism specific gene,” said Raphael Bernier, the lead author, who is UW Associate Professor in the Department of Psychiatry and Behavioral Sciences and the Clinical Director of the Autism Center at Seattle Children's Hospital.

To confirm the findings, researchers worked with scientists at Duke University who disrupted the CHD8 gene in zebra fish, and the fish developed large heads and wide set eyes. They then fed the fish fluorescent pellets and found that the fish had problems discarding food waste and were constipated.

“For years, parents of children with autism have been telling us the gastrointestinal symptoms are real, but science has been slow to respond. Now, we have clear evidence that in a subgroup of individuals with autism, both the autism symptoms and constipation are a result of the CHD8 disruptions,” Bernier said.

While researchers have previously identified Fragile X Syndrome – a genetic condition which causes autism in approximately 30% of cases – It is primarily associated with intellectual disability and attention deficits rather than autism. This is the first time researchers have shown a genetic mutation to be a definitive cause of autism.

Although less than 0.5% of all children will have the kind of autism related to the CHD8 mutation, there are many implications from this study.

Currently, autism diagnosis is based primarily on behavior. Families who are unfamiliar with the symptoms of autism may unintentionally delay diagnosis and treatment until the child is school-aged, missing years of valuable early intervention services.

The results of this study could lead the way to a "genetics-first approach" that could lead to the availability of genetic testing during pregnancy or after birth. The physical traits – subtle facial features, such as larger heads and prominent foreheads – are features that, combined with confirmation of a CHD8 gene mutation, could allow clinicians to screen babies still in utero for a higher risk of developing autism, much like clinicians now screen for physical and genetic indicators of disorders like Down’s Syndrome.

Research studies of behavioral therapies used with younger siblings of kids with autism, who are at higher risk for developing autism themselves, suggest that intervention between three to six months of age can lessen or even prevent symptoms from developing. The goal, Bernier said, is to be able to use these same exercises on babies with a higher risk of autism who have been identified before birth.

We know that if we can intervene by three or six months of age instead of later in life, we can help the child learn important social communication skills, like eye contact,” Bernier said.

Genetic testing could be offered to families as a way of guiding them on what to expect and how to care for their child. This way, early intervention services could be started as soon as possible for the best prognosis for every child.

Sources:

  1. Raphael Bernier, Christelle Golzio, Bo Xiong, Holly A. Stessman, Bradley P. Coe, Osnat Penn, Kali Witherspoon, Jennifer Gerdts, Carl Baker, Anneke T. Vulto-van Silfhout, Janneke H. Schuurs-Hoeijmakers, Marco Fichera, Paolo Bosco, Serafino Buono, Antonino Alberti, Pinella Failla, Hilde Peeters, Jean Steyaert, Lisenka E.L.M. Vissers, Ludmila Francescatto, Heather C. Mefford, Jill A. Rosenfeld, Trygve Bakken, Brian J. O’Roak, Matthew Pawlus, Randall Moon, Jay Shendure, David G. Amaral, Ed Lein, Julia Rankin, Corrado Romano, Bert B.A. de Vries, Nicholas Katsanis, Evan E. Eichler. Disruptive CHD8 Mutations Define a Subtype of Autism Early in Development. Cell, 2014; DOI: 10.1016/j.cell.2014.06.017
  2. University of Washington - Health Sciences/UW News, Community Relations & Marketing. "Genetic link to autism found, known as CHD8 mutation." ScienceDaily. ScienceDaily, 3 July 2014. <www.sciencedaily.com/releases/2014/07/140703125851.htm>.