Dozens of new genetic risks for autism uncovered

Scientists have linked 107 genes to autism, and 22 of these
genes have a significant impact on the likelihood of developing the disorder, two studies published in Nature have shown.

Researchers looked at 3,871 people with autistic
spectrum disorder (ASD) and compared their genes to those of almost 10,000 people
without the condition.

Because of the sheer amount of data generated from this research,
the researchers used new statistical methods to work out how many genes were
likely to be involved in the development of ASD. By setting their statistical
cut-off points so that their 'false discovery rate' was very low (five percent),
they found that 22 genes were implicated in ASD. But by setting the false
discovery rate to ten percent, 33 genes were associated with the disorder.

'These findings tell us that there are a relatively large
number of genes that, when damaged, substantially increase an individual's
chance of developing autism,' co-author Dr David Cutler from the Emory University
School of Medicine in Atlanta told
HealthDay. 'Autism does not have one cause, but a very, very large number
of potential causes.'

'Before these studies, only 11 autism genes had been
identified with high confidence, and we have now more than quadrupled that
number,' said Dr Stephan
Sanders, assistant professor of psychiatry at the University of California,
San Francisco, who conducted the research.

The genes were classed into three broad groups. Some were involved
in the formation of synapses, affecting how neurons send signals in the brain; some
affected transcription, thereby altering the protein that the genes code for. The
third group affected the way DNA is 'packed up' and stored within cells, which
also affects how genes are expressed.

The research has raised questions about whether genetic screening
for autism is possible.

Carol Povey, director of the National
Autistic Society's Centre for Autism, commented on the study, saying: 'Autism
is a highly complex story of genes not only interacting with other genes, but
with non-genetic factors too.'

'Research like this helps us to
understand the genetics involved in certain forms of autism and opens up the
possibility of whole families gaining a better understanding of a condition
they may share. However, we are still a long way from knowing what causes
autism.'