Using powerful leading-edge technology, researchers reveal for the first time that the true 3D structures of chromosomes are far removed from the blurry, slightly distorted X-shape many of us are familiar with. They are, in fact, complex and rather beautiful.
In a paper published online this week in Nature, researchers from The Babraham Institute and the University of Cambridge in the UK, and the Weizmann Institute in Israel, describe how, with the help of powerful computers and the latest DNA sequencers, they produced 3D visualizations of chromosomes by generating thousands of molecular measurements of them in single cells.
Funding for the new technology came from the Biotechnology and Biological Sciences Research Council (BBSRC), the Medical Research Council (MRC) and the Wellcome Trust.
The new images show that for most of the time, chromosome structures have a rich and beautiful complexity, and they also reveal how the DNA inside them folds up.
The new 3D images show a more complex side of chromosome structures. Credit: Dr. Peret Fraser. Babraham Institute.
The researchers say that the familiar X-shape is very short-lived in the life of a chromosome.
Co-author Dr. Peter Fraser, of The Nuclear Dynamics Programme at the BBSRC-funded Babraham Institute, explains:
"The image of a chromosome, an X-shaped blob of DNA, is familiar to many but this microscopic portrait of a chromosome actually shows a structure that occurs only transiently in cells - at a point when they are just about to divide."
Most cells in an organism do not have chromosomes that look like the X-shape because they have finished dividing, he says, adding that:
"Chromosomes in these cells exist in a very different form, and so far, it has been impossible to create accurate pictures of their structure."
The new 3D images show how the structure of chromosomes, and the way their DNA folds up inside them, are closely linked to when and how genes are expressed, which has a direct effect on health, disease and the process of aging.
This is the first time that chromosome structures have been generated based on measurements of them in single cells. Previous studies have calculated measurements based on averages from millions of cells.
Dr. Fraser says these new images allow them to map specific genes and to begin to unravel the principles of how chromosomes function in the genome.
Earlier this year, researchers at the Salk Institute in the US, revealed how chromosomes organize DNA during cell division by using telomeres, molecular caps that protect the ends of the chromosomes, as "anchors."