A team led by London Centre for Nanotechnology researchers, Prof. Ian Robinson and Dr. Bo Chen (now a professor at the Tongji University, Shanghai) used newly-developed serial block-face scanning electron microscopy (SBFSEM) and Thermo Scientific™ Avizo® Software, one dominant tool in 3D reconstructed image processing, to reveal the spatial structure of human chromosomes and nucleus quantitatively at high resolution of approximately 50 nm in three dimensions.
With the professionally aided processing and analysis, including the visualization features, skeletonization algorithm and quantitative modules from Avizo Software, Dr. Bo Chen and the team dove into the 3D structure of the nucleus and chromosomes. By using Avizo Software, the team dissected the nucleus and gained the information about its spatial organization. They found that the chromosomes are not only X-shaped, but also S-shaped and C- shaped, and that the larger chromosomes were more likely to be in an S-shape or C-shape, whereas the smaller chromosomes tend to be the familiar X-shape.
It also found that chromosomes are nonrandomly positioned in the prophase nucleus, with gene-rich chromosomes near the nuclear center and gene-poor ones near the periphery. The research team also deduced that the chromatin condenses locally into “visible” chromosomes during the cell cycle. Furthermore, during the chromatin condensation, the sister chromatid pairs were found not to be identical in morphology, but kept similar volumes.
3D structure of the human nucleus with chromosomes with its envelope in light blue and the chromosomes in colour.