Extensive study of the human genome has led to many new discoveries about ourselves, including details about the structure and functions of our genetic blueprints, which can aid in the development of new therapies for diseases. Many techniques have been used to help understand the intricate details of the tiny nucleic acids within our cells, but actually seeing these details with our own eyes is more of a challenge. Using a super-resolution microscopy technique, an international team led by researchers from the Center for Genomic Regulation (CRG) have imaged chromatin loops for the first time, and have also revealed more about the forces that act on our genomic structure.
The team used stochastic optical reconstruction microscopy (STORM), which is a form of super-resolution fluorescence microscopy that uses ultrahigh power lasers to activate photoswitchable fluorophores separately in resolvable subsets. The fluorophores in each subset can be precisely localized, and the images of each subset are combined to produce a final image with a resolution approximately 10 times higher than conventional fluorescence microscopy methods. By using this technique, the researchers were able to view and identify chromatin loops and cohesins within intact cells.
The study also revealed that the transcription process of DNA to RNA generates a supercoiling force that sends cohesins across the DNA strand, indirectly shaping the architecture of the genome. This new discovery shows how transcription helps to regulate chromatin looping and mediate further transcription processes in turn. This research was published in the journal Molecular Cell.
“What we have found is important because it shows the biological process of transcription plays an additional role beyond its fundamental task of creating RNA that eventually turn into proteins. Transcription indirectly compacts the genome in an efficient manner and helps different regions of the genome talk to each other,” said Vicky Neguembor, first author of the paper.
The research has implications for the understanding of genetic diseases such as Cornelia de Lange syndrome, which is caused by mutations that affect cohesins or cohesin regulators. The findings may also aid in the study of developmental disorders linked to how chromatin folds, and open up new avenues of research into genome fragility and cancer development.
Photo: DNA imaged via super-resolution microscopy. Credit: Vicky Neguembor/CRG