Scientists discover a brain signal that may trigger autism’s domino effect

When nitric oxide triggers this chain of events, an important protective protein called TSC2 begins to disappear. TSC2 normally helps regulate a major cellular control system known as mTOR, which manages processes such as cell growth and protein production. Without that safeguard, mTOR activity can surge beyond normal levels. The encouraging finding is that when scientists blocked this specific step in the chain reaction, cellular activity returned to a healthier balance. This result points to a clearer place for researchers to focus as they study autism biology and possible future treatments.

Nitric Oxide and Brain Communication

Nitric oxide is typically one of the brain's quiet helpers. This tiny molecule travels easily between cells, helping fine tune communication and keeping neural circuits responsive. However, new research from the Hebrew University of Jerusalem suggests that in certain cases of autism spectrum disorder (ASD), nitric oxide may also set off a biochemical sequence that pushes a critical cellular system into overactivity.

The work was led by Prof. Haitham Amal, The Satell Family Professor of Brain Sciences, and first-authored by PhD student Shashank Ojha. The study was published in Molecular Psychiatry, one of the leading journals in psychiatry and part of the Nature publishing group. The researchers examined how three key components interact inside brain cells: nitric oxide, the protective protein TSC2, and the mTOR pathway, which plays a central role in controlling how cells grow and produce proteins.

Scientists have long suspected that abnormal mTOR signaling may be involved in ASD. What has remained unclear is the biological pathway that links risk factors to these changes in the brain.

How Nitric Oxide Alters the TSC2 Protein

To investigate this mechanism, the team focused on a biochemical process known as S-nitrosylation. This process occurs when nitric oxide attaches to proteins and alters how they behave.

Using a systems level analysis of proteins, the researchers discovered that many proteins connected to the mTOR pathway were affected by this modification. This observation led them to examine TSC2 more closely. Under normal conditions, TSC2 functions as a brake that keeps mTOR activity under control.

Their experiments showed that nitric oxide can modify TSC2 in a way that marks it for removal from the cell. As TSC2 levels drop, its braking effect weakens and mTOR signaling rises. Because mTOR regulates protein production and other essential cellular activities, excessive activation may interfere with how neurons function and communicate.

Interrupting the Molecular Chain Reaction

The researchers then explored whether this pathway could be disrupted. They used pharmacological methods that lower nitric oxide production in neurons.

When nitric oxide signaling was reduced, the modification of TSC2 no longer occurred. As a result, mTOR activity returned to normal levels. The team also observed improvements in measurements linked to altered protein translation and autism related cellular effects in their experimental system.

In a complementary strategy, the scientists engineered a modified version of the TSC2 protein that resists nitric oxide related modification. Blocking that single chemical tag helped maintain normal TSC2 levels and reduced downstream changes associated with excessive mTOR signaling. These results support the idea that this specific modification may play an important role in driving the pathway.

Evidence From Children With Autism

The study also included clinical samples from children diagnosed with ASD. These samples came from children with SHANK3 mutations as well as those with idiopathic ASD (cases without a single known genetic cause). Participants were recruited by Dr. Adi Aran, MD.

The researchers identified patterns in these samples that matched their laboratory findings. In particular, they observed reduced levels of TSC2 and increased activity in the mTOR signaling pathway. These observations add real world relevance to the molecular mechanism identified in the study.

"Autism is not one condition with one cause, and we don't expect one pathway to explain every case," said Prof. Haitham Amal. "But by identifying a clearer chain of events, how nitric oxide-related changes can affect a key regulator like TSC2 and, in turn, mTOR, we hope to provide a more precise map for future research and, eventually, more targeted therapeutic ideas."

New Directions for Autism Research

The findings highlight the potential importance of developing nitric oxide inhibitors as possible tools for ASD research and treatment. By identifying a specific nitric oxide-TSC2-mTOR connection, the study offers a new framework for understanding how cellular signaling may become unbalanced in autism.

This clearer picture of the biological pathway could also help scientists identify new targets for therapies and guide future studies aimed at restoring normal signaling in the brain.

About Autism Spectrum Disorder (ASD)

ASD is a neurodevelopmental condition associated with differences in social communication and behavior. The condition varies widely from person to person, and many genetic and biological factors may influence risk and outcomes.

Researchers increasingly investigate cellular pathways such as mTOR because they play a crucial role in how brain cells grow, adapt, and form connections. Understanding these pathways may open new possibilities for future treatments.