Scientists have uncovered a new way in which maternal infections during pregnancy may affect the developing brain of the foetus.
"Maternal immune activation via infection during pregnancy is known to increase risk for autism spectrum disorder," say Dr Michael Lombardo of the University of Cyprus and the University of Cambridge, UK, and colleagues.
"However, it is unclear how maternal immune activation disrupts foetal brain gene expression in ways that may explain this increased risk."
The researchers examined how maternal immune activation can damage foetal brain gene expression in tests on rodents. They exposed pregnant rats to infections in the equivalent time period to the first trimester of pregnancy in humans.
This immune activation downregulated expression of genes linked to autistic spectrum disorder, the team found. It also downregulated expression of many genes known to be downregulated in the autistic spectrum disorder cortex later in life. These genes are involved in late-stage development of synapses.
Overall, maternal immune activation "may confer increased risk for autistic spectrum disorder by dysregulating key aspects of foetal brain gene expression that are highly relevant to pathophysiology affecting autistic spectrum disorder," the authors write in yesterday’s (21 March) Molecular Psychiatry.
Dr Lombardo says: "It’s important to underscore that the increase in risk is really small – too small to be meaningfully applied to specific individuals, and is only seen in very large studies when examining many thousands of people.
"Nevertheless, the biological cascade triggered by this effect is not well understood, particularly in how it may be similar to known biology behind conditions like autism. This was the motivation behind why we did the study."
Lombardo, M. V. et al. Maternal immune activation dysregulation of the fetal brain transcriptome and relevance to the pathophysiology of autism spectrum disorder. Molecular Psychiatry 21 March 2017 doi: 10.1038/mp.2017.15 [abstract]
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