Autistic kids have altered genes controlling brain development

(Bloomberg) — Autistic children have variations on genes that help neurons route themselves in the brain of a developing fetus, according to a new set of studies that provide evidence how the autistic mind’s structure may go awry.

One of the gene variants occurs 20 percent more often in autistic children and may play a role in 12 percent to 18 percent of cases of autism, according to a study published online today in the journal Nature. The altered DNA is found near a gene that is active in the development of the frontal cortex, a brain region necessary for language and judgment.

Previous studies of autistic twins suggested that genes played a major role in the disorder, according to the research report. The discovery gives scientists targets to perhaps begin developing treatments, said study author Gerard Schellenberg, a professor at the University of Pennsylvania School of Medicine, in Philadelphia.

‘When we think about treatments, those target molecules and you have to know what to target,’ Schellenberg said in a conference call with reporters today. ‘This is a major jump in terms of knowing what we need to look at.’

Families with one autistic child have a one-in-five chance of having a second, which is greater than the risk faced by the rest of the population, according to the National Institutes of Health, a U.S. agency. About 1 in 150 children in the U.S. are diagnosed with autism spectrum disorder, which is a range of behaviors including autism, according to today’s study.

Brain Wiring

The gene variants found in the new research occurs in a region of a cell’s chromosome 5 near the gene CDH10, the researchers reported in the study. Because CDH10 influences development, it provides a link between the way the brain is wired and a child’s development, the researchers said. The gene variant occurs in the normal population, so autistic children may have other high-risk variants as well, Schellenberg said.

The CDH10 pathway provides instructions for so-called neuronal cell adhesion molecules. These molecules affect how nerve cells communicate, and help shape the structure of the developing brain, the study authors said.

The research group, led by Hakon Hakonarson from the Center for Applied Genetics at the Children’s Hospital of Philadelphia, performed a genome-wide association study on DNA from more than 3,100 people in 780 families to find the genes. They replicated their results, analyzing a total of 12,834 subjects.

A second study from Hakonarson and others, also published in Nature, examined two gene pathways that help eliminate connections between nerve cells. They help produce ubiquitins, which are enzymes that help degrade connections made by the neuronal adhesion molecules. This seems to link the two discoveries together, said Hakonarson, who is also a professor at the University of Pennsylvania.

‘Both studies implicated genes involved in synaptic generation and neuronal connectivity,’ Hakonarson said. ‘This is highly consistent with previously published research.’

It also boosts a theory that autism is caused by abnormal connections between nerves in the brain, Hakonarson said.

Environment probably also plays a role in autism, Hakonarson said. In a separate study, researchers also found that children born in a breech position or to older mothers were more likely to be diagnosed with autism before the age of 8, according to the report published in the journal Pediatrics.

Autism is one of a range of ailments, known as autism spectrum disorders, that has symptoms including problems with communication, social interaction, repetitive behavior and narrow interests. Children with autism may not respond to their own name, may avoid eye contact with other people, and may rock and twirl. Autism is four times more common in men than women, according to the NIH.

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