New research into mitotic chromosomes has found that they are covered in a liquid-like coating that could allow them to bounce off one another, like bumper cars, protecting them from being damaged during cell division.

The research from Dr. Daniel Booth and Professor Amanda Wright at the University of Nottingham, in partnership with the universities of Glasgow and Kent, looked into the coatings of mitotic chromosomes, the highly condensed and organized structures that DNA morphs into during cell division. Their findings are published in the journal Nature Communications.

The mitotic chromosome periphery (MCP) is a poorly understood “coat” that covers all chromosomes. Previous work from Dr. Booth revealed that Ki-67, an important cancer biomarker, organizes the entire coat and when the coat is removed chromosomes become sticky and clump together, meaning that cells are sometimes too sick to divide properly. This raised the possibility that the MCP might have undiscovered specialist biophysical properties.

This latest work from Team Booth, led by PDRA Dr. Tania Mendonca, showed an unexpected finding—that the coat is actually liquid-like.

Chromosomes are thought to have intriguing biophysical properties; however, limitations in technology have meant this has often been difficult to explore.

In this study, using a new type of micro tweezers and analysis, the researchers captured individual chromosomes that either had too much or too little of the coat.

Using the tweezers to pull on the chromosomes, which academics liken to an Italian baker stretching pizza dough, they recorded that the liquid-coat acts as a shock absorber, allowing chromosomes to bounce off each other, potentially contributing to roles protecting against DNA damage and stopping chromosomes from being too sticky.

The academics behind this research explained that chromosomes exhibit different mechanical behaviors depending on the rate at which force is applied. At slower rates they behave in a linear, elastic manner, while at faster rates they display non-linear, viscoelastic properties.

Dr. Daniel Booth, from the University of Nottingham’s Biodiscovery Institute, said, “The chromosome periphery was first discovered nearly 150 years ago, but it remains by far the least understood chromosome compartment.”

“Only in the last 10 years, since the discovery that Ki-67 is the chief organizer, have we and other labs, been able to study chromosome periphery biology. Our latest work provides the first direct evidence that the chromosome periphery can exist in a liquid-like state, affording mitotic chromosomes force-dampening properties, which we postulate contributes to functions protecting chromosomes against DNA damage and allowing chromosomes to slide or bounce off each other to allow normal cell division.”

This work is an important step towards understanding how chromosomes and cells divide normally during mitosis and how a liquid-like coat helps this.

The research also highlights the significant role of the chromosome coating in maintaining chromosome stability and function during cell division. Understanding these mechanisms could provide insights into diseases, including cancer, where cell division processes are often disrupted.

Looking forward, the researchers will use the findings of this study to further investigate how chromosome bouncing, or lack thereof, might be involved in disease pathways.