Inside this Article:

• What the mitotic chromosome periphery is and how it influences chromosome behavior during cell division.
• How a liquid-like chromosome coating absorbs mechanical stress and prevents chromosomes from sticking together.
• Why chromosomes exhibit elastic behavior at slow deformation rates and viscoelastic behavior at faster rates.
• How micro-tweezer testing revealed force-dampening properties of chromosome coatings.
• What these findings may mean for understanding DNA damage and disease-related disruptions in cell division.

New research into mitotic chromosomes has found they are covered in a liquid-like coating that allows them to bounce off one another, protecting them from damage during cell division.

The study, conducted by researchers at the University of Nottingham in partnership with the universities of Glasgow and Kent, examined the coatings that surround mitotic chromosomes. These chromosomes are the highly condensed and organized structures that DNA forms during cell division.

At the center of the research is the mitotic chromosome periphery (MCP), a poorly understood coating that surrounds all chromosomes. Previous work showed that Ki-67, a well-known cancer biomarker, organizes this coating. When the MCP is removed, chromosomes become sticky and clump together, preventing normal cell division and causing cellular stress. These findings raised questions about whether the MCP possessed previously unidentified biophysical properties.

The new study revealed that the chromosome coating behaves like a liquid. Using a newly developed micro-tweezer system and mechanical analysis, researchers isolated individual chromosomes with varying amounts of the coating. By applying controlled forces to stretch the chromosomes — an approach likened to stretching pizza dough — the team measured how the coating responded under stress.

The results showed that the liquid-like coating acts as a shock absorber, allowing chromosomes to bounce off one another. This behavior may play a role in preventing DNA damage and reducing chromosome stickiness during mitosis.

The researchers also observed that chromosomes exhibit different mechanical responses depending on how quickly force is applied. At slower rates, chromosomes behaved in a linear elastic manner. At faster rates, they displayed non-linear viscoelastic behavior, indicating time-dependent mechanical properties linked to the liquid-like coating.

According to the research team, the chromosome periphery was first identified nearly 150 years ago, but remains the least understood compartment of the chromosome. Only within the past decade, following the discovery that Ki-67 organizes the MCP, have researchers been able to study its structure and function in detail.

The findings provide the first direct evidence that the chromosome periphery can exist in a liquid-like state, imparting force-dampening properties to mitotic chromosomes. These properties may allow chromosomes to slide or rebound from one another, supporting normal cell division while reducing the risk of DNA damage.

The study also underscores the importance of chromosome coatings in maintaining chromosome stability and function during mitosis. A better understanding of these mechanisms could provide insight into diseases such as cancer, where cell division processes are often disrupted.

Building on these results, the researchers plan to investigate whether changes in chromosome “bouncing” behavior may be linked to disease pathways.

This article is adapted from original research published by the University of Nottingham and Dr. Daniel Booth. The original article can be found here.

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