An international consortium of researchers from more than 70 universities, including the University of Utah, has reported that a study of nearly 2,300 people supports the growing consensus that autism is caused in part by rare genetic changes called copy number variants (CNVs).
The study findings, constituting the results of the second phase of the Autism Genome Project (AGP), were published in Nature on June 9, 2010. The study also identifies several new genes and pathways that appear to contribute to the susceptibility to autism and related autism spectrum disorders (ASDs). Autism Speaks, an autism science and advocacy organization, is a major sponsor of the AGP.
Hilary Coon, Ph.D., a lead author on the study and research professor of psychiatry at the University of Utah School of Medicine, said while research shows scientists are making progress in understanding the causes of autism, it is increasingly clear that autism is a multifaceted disorder with both genetic and environmental causes. "We are whittling away at it," Coon said. "But a brain-related disorder, such as autism, is amazingly complex. It's not really one entity."
Autism is a neurobiological disorder that inhibits a person's ability to communicate and develop social relationships, and is often accompanied by behavioral challenges. Autism spectrum disorders are diagnosed in one in 110 children in the United States, affecting four times as many boys as girls. The prevalence of autism increased 57 percent from 2002 to 2006. The Centers for Disease Control and Prevention have called autism a national public health crisis whose cause and cure remain unknown.
The researchers enlisted 996 people with autism and 1,287 without the disorder - including participants from more than180 Utah families. The study focused on more than 100 genes previously implicated in ASD and intellectual disability, and found that those with autism carried a higher number of rare CNVs - small deletions or additions to the DNA sequence - than those without the disorder. The researchers found that while some of these CNVs are inherited, others are new variations in individuals with autism. The specific consequences of each CNV aren't known, but in those with autism they may alter the function of those genes.
These CNVs are found in an estimated 1 percent of the population and could account for up to 3.3 percent of autism cases, according to the study. While that is a relatively small percentage, it represents many thousands of people with the disorder.
Along with the CNVs, the study also identified three new genes and the chromosomal locations (loci) of two other genes the researchers believe make individuals more susceptible to autism. These genes - SHANK2, SYNGAP1, DLGAP2 and the DDX53-PTCHD1 loci (on the X chromosome) - belong to synaptic pathways that allow neurons to conduct electrical and chemical signals and are involved in cellular proliferation and intracellular signaling. Identifying these genes could aid in the search for new therapies to treat autism. But even if it proves possible to develop new drugs that target those genes, it will take many years to accomplish.
Anne Bang joins research to understand the genetic underpinnings of psychiatric conditions