Paternal sperm holds clues to autism

Researchers from the Johns Hopkins University have found that DNA from the sperm of men whose children had early signs of autism shows distinct patterns of tags that could contribute to the condition.

Most experts agree that autism is usually inherited since the condition tends to run in families.

In this study, investigators looked for possible causes for the condition not in genes themselves, but in the "epigenetic tags" that help regulate genes' activity.

"We wondered if we could learn what happens before someone gets autism," said Andrew Feinberg, director of the Centre for Epigenetics at the Johns Hopkins University's school of medicine.

"If epigenetic changes are being passed from fathers to their children, we should be able to detect them in sperm," added co-lead investigator Daniele Fallin from the Bloomberg School of Public Health.

The team assessed the "epigenetic" tags on DNA from sperm from 44 fathers.

Early in the pregnancy, a sperm sample was collected from fathers enrolled in the study.

One year after the child was born, he or she was assessed for early signs of autism using the Autism Observation Scale for Infants (AOSI).

The researchers collected DNA from each sperm sample and looked for epigenetic tags at 450,000 different positions throughout the genome.

They found 193 different sites where the presence or absence of a tag was statistically related to the AOSI scores.

"Of particular interest was that four of the 10 sites most strongly linked to the AOSI scores were located near genes linked to Prader-Willi syndrome -- a genetic disorder that shares some behavioural symptoms with autism," the authors wrote.

Several of the altered epigenetic patterns were also found in the brains of individuals with autism, giving credence to the idea that they might be related to autism.

The team now plans to confirm its results in a study of more families and to look at the occupations and environmental exposures of the fathers involved.

There is currently no genetic or epigenetic test available to assess autism risk.

The findings were detailed in the International Journal of Epidemiology.