In the largest study of its kind to date, NARSAD Grant-supported researcher Jonathan Mill, Ph.D., of King's College London and the University of Exeter, and team studied 100 identical twins, including some with autism spectrum disorder (ASD), in an attempt to identify causes of the disorder beyond genetic predisposition. They identified distinctive patterns of changes in the expression of genes—“epigenetic” changes—that may be caused by environmental influences that affect the expression of genes without altering the underlying genetic code (or DNA). Their findings were published online today in Molecular Psychiatry.
Previous studies have demonstrated a strong genetic link to developing ASD, but genetic predisposition does not necessarily determine the manifestation of illness: with identical twins—who share the same DNA—it is only in approximately 70% of the cases that both identical twins have ASD. This suggests non-genetic, or epigenetic, factors are involved. The research team examined over 27,000 sites across the genome (all of the subject’s hereditary information) using samples taken from 50 identical twin pairs to study an epigenetic process called DNA methylation. DNA methylation can silence gene expression.
ASD affects approximately 1 in 100 people in the United States and the United Kingdom and affects people to varying degrees. People with ASD show symptoms across three common areas: deficits in social interactions and understanding, repetitive behavior and interests, and impairments in language and communication.
Dr. Jonathan Mill
, study lead author and Professor, King's College London's Institute of Psychiatry
and the University of Exeter Medical School, says: "Research into the intersection between genetic and environmental influences is crucial because risky environmental conditions can sometimes be avoided or changed. Epigenetic changes are potentially reversible, so our next step is to embark on larger studies to see whether we can identify key epigenetic changes common to the majority of people with autism to help us develop possible therapeutic interventions."
The researchers identified distinctive patterns of DNA methylation associated with autism diagnosis, behavioral symptoms and increasing severity of symptoms. These findings offer new insight into how—and where in the genome—environmental factors can turn genetic predisposition into actual development of ASD. This work may offer new targets for treatment and/or prevention of ASD.