For the first time, scientists have done large-scale sequencing to compare the brains of healthy people with those who have autism.

They took more than 200 frozen post-mortem brain tissue samples from about 90 healthy individuals and people with autism. The samples were then mashed up and DNA was extracted with the attached proteins.

The DNA in our cells is wound around spools called nucleosomes, explained Dr Shyam Prabhakar, senior author of the study and associate director of integrative genomics at Agency for Science, Technology and Research's Genome Institute of Singapore (GIS). It is packaged this way so the DNA is compact enough to fit into the nucleus.

Antibodies were used to extract the loosely packed DNA, which was then sequenced. The scientists looked at the number of sequences they got from the samples. The more "unpacked or loose" the DNA was, the more DNA sequences there were. Scientists then compared the number of DNA sequences for both groups and found that those in autistic individuals differed from those in healthy people.

Many parts of the DNA sequences found in samples from autism patients were either more unpacked, or more packed, than those found in healthy individuals, deviating from the norm, said Dr Prabhakar. And despite the different traits exhibited by those with autism, the changes in DNA packaging were shared by them.

Led by GIS, the project, part of the International Human Epigenome Consortium, also involved researchers from the University of California at Los Angeles, and the University of Exeter and King's College London in Britain. "Being part of such a multinational consortia enables us to significantly impact research while sharing our findings with scientists throughout the world," said joint lead author of the study Dr Jeremie Poschmann, Research Fellow at the University of Exeter.

The study is part of a collection of 41 publications in top scientific journal Cell, as well as science journals.

Carolyn Khew