A team of researchers from the University of Pittsburgh and Carnegie Mellon University has discovered that brain cells from people with Alzheimer's disease show a previously unknown pattern of genome reorganization, detected through advanced 3D mapping and artificial intelligence analysis. The finding, published in Science, reveals that the three-dimensional structure of DNA itself may play a critical role in Alzheimer's disease biology, offering a new layer of understanding beyond the disease's well-known hallmarks like amyloid plaques and tau tangles.

What Is Compartment Mingling and Why Does It Matter?

The research centers on a phenomenon the team calls "compartment mingling." Chromatin, the complex of DNA and proteins that packages genetic information into a cell's nucleus, normally organizes into distinct active and inactive regions. In Alzheimer's brain cells, these regions become less clearly separated, creating a blurred boundary between active and inactive genetic zones.

Using a breakthrough single-cell 3D genome mapping technique developed by Carnegie Mellon computer scientist Jian Ma and colleagues, researchers analyzed postmortem brain tissue from the prefrontal cortex, a region at the front of the brain, obtained from individuals with and without Alzheimer's disease. The analysis revealed that multiple types of brain cells in Alzheimer's patients showed fewer short-range genetic contacts and more long-range contacts, along with greater compartment mingling overall.

"Alzheimer's disease cannot be understood one layer at a time. The genome's 3D structure is a fundamental regulatory layer that helps to connect DNA sequence to gene activity. By integrating genome folding, cell state and tissue context, we can move beyond cataloging disease-associated changes toward understanding how they fit together and which mechanisms to test next," said Jian Ma, Ray and Stephanie Lane Professor of Computational Biology at Carnegie Mellon University.

Jian Ma, Ray and Stephanie Lane Professor of Computational Biology at Carnegie Mellon University

The altered genome organization was linked to reduced neuronal and synaptic programs, altered metabolic and stress responses, and changes in microglia, the brain's immune cells. Contacts between genes and nearby regulatory elements that normally control gene activity also weakened in Alzheimer's brain cells.

How Did Researchers Connect Genome Structure to Disease?

The research team employed multiple complementary technologies to build a comprehensive picture of how genome organization relates to disease. They used GAGE-seq, a technique that measures gene expression and 3D genome contacts within individual cells simultaneously. They also integrated these measurements with spatial transcriptomic maps of intact brain tissue, allowing them to place molecular changes within their broader tissue context.

A major breakthrough was the development of Hicformer, a deep learning artificial intelligence model that combines DNA sequence information, broad genome-folding features, and local 3D contact maps to predict gene activity in different types of brain cells. The researchers describe it as a computational "test bed" for exploring how altered genome folding may change gene activity and contribute to disease.

Steps to Understanding Alzheimer's Through Genome Architecture

• Single-Cell Analysis: Researchers examined individual brain cells from people with and without Alzheimer's disease, revealing cell-to-cell variations in genome organization that would be invisible in bulk tissue studies.
• 3D Mapping Technology: Advanced imaging and sequencing techniques captured the three-dimensional folding patterns of DNA, showing how genetic material physically organizes within the nucleus.
• AI-Powered Integration: Machine learning models combined multiple data types, including DNA sequence, genome folding patterns, and gene activity measurements, to identify disease-associated changes and predict their functional consequences.

The research team included doctoral students Alexander K. Kunisky and Jude Baroudi from the University of Pittsburgh, along with collaborators from the Broad Institute of MIT and Harvard, UCLA, the University of Washington, and the Rush Alzheimer's Disease Center.

What Questions Does This Discovery Raise for Future Research?

The findings open multiple research pathways, according to Hansruedi Mathys, assistant professor of neurobiology at the University of Pittsburgh and cosenior author of the study. Key questions include whether the differences in genome structure cause the disease pathology or whether the pathology causes the changes; why some people develop these genome alterations while others do not; and whether people who show signs of Alzheimer's pathology but have no clinical symptoms also display the altered genome organization.

"We know the classic hallmarks of Alzheimer's disease, accumulation of amyloid-beta plaques and tau tangles, but our results establish higher-order chromatin alterations as a component of the molecular pathology associated with the disease, which currently affects seven million Americans, a number that continues to grow," said Hansruedi Mathys.

Hansruedi Mathys, Assistant Professor of Neurobiology at the University of Pittsburgh

Mathys emphasized that understanding the disease's fundamental biology is essential for developing preventive therapies. "If we don't know what is happening in Alzheimer's disease, we can't think of ways to prevent it. So, if we're ever going to stop Alzheimer's, understanding it must be a top priority," he stated.

Mathys

The research was supported by multiple National Institutes of Health grants, including funding from the NIH Common Fund's 4DN Program and SenNet Program, reflecting the government's recognition of the importance of understanding genome organization in disease. While the team focused on Alzheimer's disease, the technology could potentially be applied to numerous other conditions, offering a new framework for understanding how genome architecture contributes to human disease.