Researchers have identified more than 2,000 of these regulatory regions – markers on top of our DNA that affect how our genetic machinery operates on a functional level – which are involved in learning and strongly associated with ASD.
While we know many cases of ASD are tied to differences in our genetic coding, the findings suggest epigenetic factors affecting non-genetic sequences of DNA could account for the development of the condition in many individuals.
"Our proof-of-concept study demonstrates the feasibility of going after genetic components of autism that are outside of genes and may eventually lead to improvements in the diagnosis and treatment of autism," says neuroscientist Lucia Peixoto from Washington State University.
Epigenetics is a burgeoning field of science looking at how we inherit traits and changes from environmental or external sources, not just the DNA code that otherwise instructs how our bodies should grow and function.
These kinds of epigenetic mechanisms – which modify how our DNA is expressed at a molecular level – mean experiences in childhood can change our genetic code ever after, with things like babies being biochemically transformed by the amount of cuddles they receive.
In some cases, epigenetic 'memories' can be passed down as far along as 14 generations, so there's clearly a lot more than just DNA affecting our biological destiny.
In their own study, Peixoto and her team experimented with mice that were placed in a box and given a small shock, which conditioned them to associate the box with an unpleasant experience.
When DNA from the animals' hippocampus (which processes memory) was later analysed, the researchers found that chromatin – macromolecules that help 'package' DNA inside cells – had become more accessible.
With a new bioinformatics tool they developed called DEScan (Differential Enrichment Scan), the team identified 2,365 regions which were epigenetically regulated following the mouse's conditioning. Interestingly, genes near many of these regions are known risk genes for ASD.
One of the more well-known autism risk genes is called Shank3, which is missing in a small percentage of autism patients. In a previous study, researchers found that by switching this gene on in mice that were engineered without the active Shank3 gene, autism symptoms could be reversed.
In the present research, the team analysed a clinical study involving more than 700 children (some 550 of which had autism), and found that one of the regulatory regions they identified in mice – called rs6010065 – is indeed associated with ASD in humans.
There's obviously still a huge amount of research to be done here before we know more about how these epigenetic controls might be impacting the development of autism in children, but the researchers are convinced we could have a bright new lead to follow up on.
"One of the major challenges in the genetics of disease is understanding the role of the vast portions of the genome that regulate gene expression," says one of the researchers, neuroscientist Ted Abel from the University of Iowa.
"[A]ctivity-dependent changes in chromatin accessibility may hold the key to understanding the function of this ' dark matter' of the genome and may provide novel insights into the nature of autism and other neurodevelopmental disorders."
The findings are reported in Science Signaling.