Mouse spatial transcriptomics implicates the thalamus and cortex in autism and schizophrenia

For decades, scientists have known that conditions like autism and schizophrenia are deeply rooted in our genes. We have identified hundreds of specific genes that increase the risk of developing these disorders. However, knowing the genetic list is only half the story. To understand how these conditions actually work, researchers must locate where in the brain these genes are most active. It is a bit like finding a specific engine part in a car; knowing the part exists is useful, but knowing exactly which engine it belongs to is what allows you to fix the car. For complex brain disorders, the "engine" is the entire brain, and pinpointing the exact regions involved has been incredibly difficult because the brain is vast, and the genetic signals are often subtle and spread out.

A team of researchers at the University of California, San Francisco, and the University of Oxford has taken a new approach to solve this puzzle. Instead of looking at the brain as a whole or focusing on just one small piece, they used a technology called spatial transcriptomics. This method allows scientists to see which genes are turned on in specific locations within a tissue sample, essentially creating a map of genetic activity across the brain. By applying this technique to the brains of adult mice, the researchers were able to scan a wide cross-section of the brain and measure the activity of genes known to be linked to autism and schizophrenia. Their goal was to see if these risk genes cluster together in specific neighborhoods of the brain, which would suggest those areas are central to the disorders.

The researchers began by preparing thin slices of brain tissue from adult mice, capturing a view that stretched from the front of the brain to the back and from the top to the bottom. They placed these slices onto a special slide that could capture genetic material from thousands of tiny spots across the tissue. After sequencing the genes found in each spot, they used computer algorithms to group the spots into distinct clusters based on their genetic profiles. These clusters naturally aligned with known anatomical structures, such as the cortex (the outer layer of the brain), the hippocampus (involved in memory), and the thalamus (a relay station deep in the brain). To ensure their findings were accurate, the team corrected for the fact that some brain regions naturally contain more nerve cells than others, ensuring that the results reflected true gene activity rather than just cell density.

When they analyzed the genes associated with autism, the researchers found a striking pattern. The genes were not evenly distributed; instead, they were most heavily concentrated in the thalamus, a deep brain structure that connects different parts of the brain. The cortex and the main olfactory bulb, which processes smells, also showed high levels of these genes. This was a significant discovery because, while the cortex has long been suspected in autism, the thalamus had not been highlighted as a primary hotspot in the same way. The researchers noted that this enrichment was so strong that even if they removed the most active gene from the analysis, the thalamus remained the top location. They also found that specific genes, such as those involved in cell communication and signaling, were particularly active in the thalamus compared to other areas.

The picture for schizophrenia was similar but with some distinct differences. The genes linked to schizophrenia were also highly enriched in the thalamus and the cortex. However, in addition to these, the hippocampus showed a much stronger signal for schizophrenia than it did for autism. The olfactory bulb was also a major hotspot for schizophrenia genes. The researchers observed that while the two disorders share some genetic ground—both showing strong activity in the thalamus and cortex—they also have unique signatures. For instance, the hippocampus appeared to play a more prominent role in schizophrenia, whereas the thalamus was the single most enriched region for autism.

The study also looked at how these findings might relate to the symptoms of these disorders. The researchers pointed out that the thalamus acts as a bridge between the senses and the cortex, helping to filter and process information. The fact that autism-related genes are so active here suggests that the disorder might involve a fundamental issue with how the brain filters and connects sensory information. Similarly, the strong presence of schizophrenia genes in the hippocampus and thalamus aligns with the memory and sensory processing difficulties often seen in the condition. The researchers emphasized that these findings do not mean that a single part of the brain causes these disorders. Instead, the results suggest that these conditions arise from complex interactions across multiple brain regions, with the thalamus and cortex serving as critical hubs.

While the study provides a clear map of where these genes are most active, the researchers were careful to note its limitations. The study was conducted on adult mice, and the brain changes during development, so the results might look different in a developing human brain. Additionally, the slices they analyzed did not include every part of the brain, such as the cerebellum or the amygdala. Despite these constraints, the work offers a powerful new way to visualize the genetic landscape of the brain. By showing that autism and schizophrenia genes cluster in specific, shared, and distinct regions, the study moves the field closer to understanding the physical circuits that underlie these complex conditions. It suggests that future treatments might need to target these specific networks rather than the brain as a whole, offering a more precise path forward for understanding and treating these challenging disorders.