In a major advance in genetics, scientists at Northwestern University have uncovered what researchers describe as a hidden second layer of human DNA. By mapping how the genome folds and shifts inside living cells, the team has revealed how the physical structure of DNA helps control gene activity.
The research, conducted with the 4D Nucleome Project and published in Nature, offers a new understanding of how genetic instructions operate beyond the DNA sequence itself.
DNA folding shapes gene activity
Scientists found that DNA inside the nucleus does not exist as a straight strand. Instead, it folds into loops and forms compartments that bring distant regions into contact.
These structures act as a control system, helping determine which genes are switched on or off at any given time. Researchers say this three-dimensional organization plays a central role in how cells develop, function, and respond to their environment.
Co-corresponding author Feng Yue said understanding genome folding is essential to understanding how cells work. He explained that the spatial arrangement of DNA directly influences gene behavior over time.
High-resolution maps reveal genome architecture
The team used human embryonic stem cells and fibroblasts to build detailed maps of genome organization. Their analysis identified more than 140,000 chromatin loops in each cell type. These loops connect distant parts of the genome and help regulate gene expression.
Researchers also classified chromosomal domains and mapped their positions within the nucleus. In addition, they created high-resolution three-dimensional models of entire genomes at the single-cell level. These models show how genes are arranged relative to nearby regulatory regions and how these arrangements vary from one cell to another.
Scientists uncover a hidden second layer of human DNA. New 3D genome maps show how DNA folding not just sequence controls gene activity, cell function, and disease risk. This breakthrough could reshape how we study cancer, and future therapies. #Genetics #DNA pic.twitter.com/3jvF67BANt
— Tom Marvolo Riddle (@tom_riddle2025) March 23, 2026
Scientists report that these differences are closely linked to essential cellular processes, including gene transcription and DNA replication. This helps explain how cells with the same DNA can perform very different functions.
New tools predict genome folding
To capture the complexity of genome organization, the researchers combined several advanced genomic techniques and compared their performance. This benchmarking allowed them to identify which methods are best suited for detecting loops, defining domain boundaries, and tracking subtle changes in DNA structure.
The team also developed computational tools that predict DNA folding from its sequence alone. These models allow scientists to estimate how genetic variants may affect genome structure without performing complex lab experiments.
Implications for disease and future therapies
Researchers report that the findings could accelerate the discovery of disease-causing mutations. Many genetic variants linked to disease are located in non-coding regions of DNA. These regions do not produce proteins but play a key role in regulating gene activity. Changes in these areas may disrupt DNA folding and lead to disease.
The study also has implications for cancer research. Scientists have already observed changes in genome structure in cancers such as leukemia and brain tumors. Yue said future work will focus on targeting these structural changes using treatments such as epigenetic inhibitors.
Experts say the research supports a growing view that DNA sequence alone does not fully explain how genes work. The physical shape of the genome acts as a second layer of information that controls gene activity.
Toward a new understanding of human genetics
By linking DNA folding, chromatin loops, and gene regulation, the study provides a more complete picture of how genetic instructions function inside cells. Scientists report that this new perspective could lead to improved diagnostic tools and more precise therapies based on genomic structure.
The findings mark an important step toward understanding how this hidden second layer of DNA influences human health and disease.
