p70 ribosomal protein S6 Kinase (p70S6K) as a potential peripheral biomarker for autistic symptoms in 16p11.2 deletion and duplication syndromes

The human brain is a vast network of connections, constantly building and reshaping itself to learn, remember, and react to the world. This intricate construction relies on a delicate balance of chemical signals that tell cells when to grow, when to stop, and how to communicate. When these signals go awry during early development, the result can be neurodevelopmental disorders, conditions that affect how a person thinks, behaves, and interacts with others. For decades, doctors have diagnosed these conditions by observing behavior and testing cognitive skills, a process that is often lengthy and subjective. Scientists have long sought a more direct way to understand these disorders, hoping to find a biological clue—a biomarker—in the blood that could reveal what is happening inside the brain. The goal is to move beyond guessing based on symptoms and toward understanding the specific molecular machinery that has gone wrong, which could eventually lead to better treatments and earlier support.

One such area of focus involves a specific region on chromosome 16, known as 16p11.2. In some people, this section of genetic material is missing, while in others, it is duplicated. These variations are surprisingly common, occurring in roughly one in every two thousand births for the missing piece and one in every eleven hundred for the extra piece. Both scenarios create a high risk for a range of challenges, including intellectual disability, autism, attention deficits, and anxiety. However, the experience varies wildly from person to person; some individuals with the same genetic change struggle profoundly, while others function with relative ease. This unpredictability makes it difficult to forecast a child's future needs or to tailor treatments effectively. Researchers have suspected that the genes in this region control a major signaling pathway involved in protein production, a process essential for building the brain's connections, but they lacked evidence of how these changes manifest in living people.

A team of researchers set out to bridge this gap by studying children and young people with these 16p11.2 variations. They recruited families from clinics and support groups across the United Kingdom, gathering a group of 45 children with the deletion, 29 with the duplication, and 30 siblings who did not carry these genetic changes to serve as a comparison group. The team conducted a deep dive into the participants' lives, using detailed interviews and standardized tests to measure their cognitive abilities, motor skills, and the severity of their psychiatric symptoms. They also collected blood samples from a subset of these participants to look for physical evidence of the genetic changes in their cells. Specifically, they examined peripheral blood mononuclear cells, a type of white blood cell that can be easily accessed and analyzed, to see if the molecular signals inside them mirrored the known genetic differences.

The study confirmed what previous research had suggested: children with either the deletion or the duplication faced significantly greater challenges than their siblings. They scored lower on intelligence tests and showed higher levels of anxiety, mood disorders, and autistic traits. Interestingly, the researchers found that while both groups struggled, the children with the duplication tended to have more severe behavioral issues, particularly regarding attention and oppositional behavior, compared to those with the deletion. This distinction highlighted that while the two conditions are mirror images genetically, they do not produce identical outcomes. The team then turned their attention to the blood samples, looking for changes in specific proteins that act as messengers in the cell's signaling network. They focused on two main pathways: one involving a protein called ERK, which is directly linked to the genes on chromosome 16, and another involving a protein called p70S6K, which is part of a broader system that controls how cells build new proteins.

The results in the blood samples were revealing. As expected, the levels of the ERK protein reflected the genetic dosage: children with the duplication had higher levels of this protein, while those with the deletion had lower levels. This confirmed that the genetic change was directly visible in the blood. However, the story for the second protein, p70S6K, was different. Regardless of whether a child had the deletion or the duplication, their levels of p70S6K were significantly lower than those of the control group. This finding was unexpected because the two genetic conditions are opposites, yet they both led to the same reduction in this specific protein. More importantly, the researchers discovered a link between this protein and the children's symptoms. The lower the level of p70S6K in a child's blood, the more severe their autistic traits tended to be. This relationship held true across both the deletion and duplication groups, suggesting that the amount of this protein might serve as a biological indicator for the intensity of autism-related symptoms, independent of which specific genetic change the child carries.

The study also looked at other proteins in the same signaling chain to see if they told a similar story. They found that while some proteins changed in ways that matched the genetic dosage, others did not show a clear link to the severity of the children's symptoms. For instance, a protein called phospho-AKT was slightly higher in the deletion group, but this increase did not correlate with how severe the behavioral or cognitive challenges were. This suggests that the signaling network is complex, and not every change in protein levels translates directly to the symptoms a person experiences. The researchers were careful to note that while the link between p70S6K and autism symptoms was strong, it was not a simple cause-and-effect relationship that they could prove with this single study. The analysis showed that the genetic change itself explained much of the variation, and the protein levels might be part of a larger, interconnected system rather than a single switch.

Despite these nuances, the findings offer a promising new direction for understanding these disorders. The ability to detect a specific protein reduction in a simple blood test that correlates with the severity of autistic traits is a significant step forward. It suggests that the biological roots of these symptoms can be found outside the brain, in cells that are much easier to study. The researchers acknowledge that their study had limitations, including a relatively small number of participants and the fact that they took a single snapshot in time rather than following the children over many years. They also noted that their approach was targeted, looking at specific proteins they already suspected were important, rather than scanning the entire landscape of proteins in the blood. Nevertheless, the work provides a concrete foundation for future research. It points to p70S6K as a potential candidate for a biomarker that could help doctors understand the risk profile of a child with a 16p11.2 variation, potentially guiding more personalized care and opening the door to therapies that target the underlying molecular machinery rather than just the symptoms.