Are Multiple Neurodevelopmental Disorders More Like One-Size-Fits-All?

New research has found that multiple neurodevelopmental disorders have a common molecular cause, suggesting that a one-size-fits-all therapeutic approach could be effective for conditions ranging from Down syndrome to autism.

Neurodevelopmental disorders, including Down syndrome and autism-spectrum disorder, as well as seizures and attention-deficit hyperactivity disorder, can have profound, lifelong effects on learning and memory. However, relatively little is known about the molecular pathways affected by these diseases.

"Neurodevelopmental disorders are rare, meaning trying to treat them is not efficient," senior study author Carl Ernst of McGill University said in a press release. "Once we fully define the major common pathways involved, targeting these pathways for treatment becomes a viable option that can affect the largest number of people."

Ernst and colleagues behind a new study, published in the American Journal of Human Genetics, show that neurodevelopmental disorders caused by distinct genetic mutations produce similar molecular effects in cells.

Common variants in the same gene have been associated with two or more different disorders, but mutations in many different genes can lead to similar diseases. And until now, scientists weren't sure whether genetic mutations that cause neurodevelopmental disorders affect distinct molecular pathways or converge on similar cellular functions.

To address this question, Ernst and his team used human fetal brain cells to study the molecular effects of reducing the activity of genes that are mutated in two different autism-spectrum disorders. 18q21 deletion syndrome is caused by changes in transcription factor 4 (TCF4), whereas mutations in euchromatic histone methyltransferase 1 (EHMT1) cause a disease known as 9q34 deletion syndrome. Both conditions have similar symptoms, including intellectual disability and psychiatric problems.

By interfering with the activity of TCF4 or EHMT1, researchers noticed similar molecular effects in the fetal brain cells.

"Our study suggests that one fundamental cause of disease is that neural stem cells choose to become full brain cells too early," Ernst explained. "This could affect how they incorporate into cellular networks, for example, leading to the clinical symptoms that we see in kids with these diseases."