New Insights into Genetic Basis of Autism

UNSW Australia scientists have discovered a link between autism and genetic changes in some segments of DNA that are responsible for switching on genes in the brain.

The finding is the result of a world-first study of the human brain that identified more than 100 of these DNA segments, known as enhancers, which are thought to play a vital role in normal development by controlling gene activity in the brain.

“Our study provides a unique resource of information on gene function in the human brain which could help reveal the basis of autism and related neurological disorders,” says lead author UNSW’s Dr Irina Voineagu.

The research is published in the journal Nature Neuroscience.

A lot of research on the genetic causes of diseases, including autism, focuses on mutations in genes – the segments of DNA that contain the blue-print for producing proteins in the cell. But protein-coding DNA accounts for less than 5 per cent of the full human genetic code.

“The rest of the DNA is not just a lot of junk. Some segments of it – the enhancers – control when, and in which parts of the body, the genes become active,” says Dr Voineagu, of the UNSW School of Biotechnology and Biomolecular Sciences.

“These enhancers can harbour disease-causing mutations which would be missed in traditional studies of genes, but which are suspected of playing an important role in inherited neurodevelopmental and neuropsychiatric disorders.

“The problem for researchers is that enhancers are hard to find, because they can be located a long way away from the genes that they control.”

In their comprehensive study, which involved a search of gene activity maps as well as testing of human brain tissue, the researchers identified more than 100 enhancers which were much more active in the brain than in other tissues.

This image shows the word Autism made up with building blocks.
In their comprehensive study, which involved a search of gene activity maps as well as testing of human brain tissue, the researchers identified more than 100 enhancers which were much more active in the brain than in other tissues. Image credit: Columbia University School of Nursing / CTRPhotos.

They did this by searching for the special RNA molecules that enhancers produce.

They also provided initial evidence towards identifying which genes were being switched on by the enhancers.

In a final step they also analysed whether any of the enhancers contained genetic changes already linked to a range of disorders including, attention deficit disorder, depression, bipolar disorder, schizophrenia and autism.

The results were positive for autism.

“Our study is the first to investigate how the activity of enhancers and genes are coordinated in the human brain, and the first to show that brain enhancers are linked to autism,” says Dr Voineagu.

About this autism research

Source: Susan Griffith – Case Western Reserve
Image Credit: Image is credited to Columbia University School of Nursing / CTRPhotos adapted from a previous Columbia University press release featured on NeuroscienceNews
Original Research: Abstract for “Coexpression networks identify brain region–specific enhancer RNAs in the human brain” by Pu Yao, Peijie Lin, Akira Gokoolparsadh, Amelia Assareh, Mike W C Thang and Irina Voineagu in Nature Neuroscience. Published online July 13 2015 doi:10.1038/nn.4063


Abstract

Coexpression networks identify brain region–specific enhancer RNAs in the human brain

Despite major progress in identifying enhancer regions on a genome-wide scale, the majority of available data are limited to model organisms and human transformed cell lines. We have identified a robust set of enhancer RNAs (eRNAs) expressed in the human brain and constructed networks assessing eRNA-gene coexpression interactions across human fetal brain and multiple adult brain regions. Our data identify brain region–specific eRNAs and show that enhancer regions expressing eRNAs are enriched for genetic variants associated with autism spectrum disorders.

“Coexpression networks identify brain region–specific enhancer RNAs in the human brain” by Pu Yao, Peijie Lin, Akira Gokoolparsadh, Amelia Assareh, Mike W C Thang and Irina Voineagu in Nature Neuroscience. Published online July 13 2015 doi:10.1038/nn.4063

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  1. If it is all neurological then why does it seem that with probiotics, gluten free diet or antibiotics help many on the spectrum? Why is it that our child can be a typical toddler than out of the blue just be different? What about more gut related studies bc there seems to be a relation. I dotn know how true but one person said he is friends with a top doctor that said many autism cases are misdiagnosed lyme disease? I don’t know if I believe that, I have actually never heard that one before

    1. The brain doesn’t fully form for males until the early twenties. That’s why males do more stupid stuff growing up. Girls do so sooner. The brain isn’t a blank slate in newborns as hypothesized in the past, but there is tremendous growth after birth. That doesn’t mean that it currently can be stopped from being autistic. This research suggests a new way to intervene and help…

    2. Well, autism isn’t progressive and its symptoms may actually get better over time. And so when a new diet is started and the child is improving it may look as though the diet is what caused it but it may be that they would just improve regardless. I’m no expert though.

    3. @Crystal: Why would you thin that gut microbiome effects on the central nervous system were not “neurological” –I think your concepts are based in a false dichotomy. There are undoubtedly some neurological effects caused by the gut microbiome, not least because specific organisms in that microbiome produce neurostransmitters. It’s not a case of either/or but both/and. There are lots of gut related sutdies and these will reveal a great deal, but those gut interactions are happening in the broader gene-environment context of the individual. This research into eRNA mechanisms helps to understand that bigger picture. There is so much to learn about this and it’s never been a better time to learn. There is no reason to pollute the quest for knowledge with ideological side-taking or political posturing.

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