A human cell contains an enormous 1.8 metres of DNA partitioned into 46 chromosomes. These have to be copied and distributed equally into two daughter cells at every division. Condensation, the shortening of chromosomes, allows the cell to handle such huge amounts of genetic material during cell division and helps preventing fatal defects in chromosome separation. Now researchers from the European Molecular Biology Laboratory (EMBL) for the first time tracked chromosome condensation in mammalian cells over the entire course of cell division. In this week’s advanced online publication of Nature Cell Biology they report crucial new insights into timing, function and molecular basis of chromosome condensation.
What happens when chromosomes are not correctly separated and distributed during cell division we know very well; two daughter cells with either broken chromosomes or different numbers of chromosomes result and severe diseases including cancer can arise. But so far we know only little about condensation, a process crucial to the successful separation of chromosomes. Using powerful microscopes, researchers led by Jan Ellenberg at EMBL looked at living mammalian cells to find out how and when chromosomes shorten during cell division.
Condensation begins early, when the cell starts preparing for division, and the chromosomes become shorter and shorter until they are about to separate and migrate towards the poles of the cell.
“It is at this stage that textbooks say chromosomes are shortest. Then, after separating they would expand again,” says Ellenberg. “But we found something very different. Shortly after they finish separating, chromosomes actually condense even further. This makes sense, because in this way they are shortest when the physical division of one cell body into two takes place. Like this, no long chromosome arms extend over the plane of division, because that could expose the DNA to serious mechanical damage.”
The extreme condensation of chromosomes towards the end of cell division can also serve as a safety net if something goes wrong with chromosome separation in earlier phases of division. When the researchers added chemicals to the cell to block the late condensation, more separation defects appeared.
“Sometimes chromosomes get stuck and cannot be fully separated by the spindle that normally distributes them into the daughter cells,” says Felipe Mora-Bermúdez, who carried out the experiments in Ellenberg’s lab, “we think that the ‘super condensation’ at later stages helps to disentangle such chromosomes and acts as a back-up mechanism to rescue separation defects.”
The EMBL researchers found that an enzyme called Aurora kinase is crucially involved in this process. Blocking this enzyme abolishes late condensation of chromosomes. They now hope to uncover the detailed molecular mechanism underlying the late shortening of chromosomes. This could further advance our understanding of cell division and the risk factors that lead to defects in chromosome separation and their dramatic consequences.
Anna-Lynn Wegener | alfa
Cancer diagnosis: no more needles?
25.05.2018 | Christian-Albrechts-Universität zu Kiel
Less is more? Gene switch for healthy aging found
25.05.2018 | Leibniz-Institut für Alternsforschung - Fritz-Lipmann-Institut e.V. (FLI)
The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.
Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...
A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.
The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...
At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.
At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...
There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?
At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...
So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics
Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...
25.05.2018 | Event News
02.05.2018 | Event News
13.04.2018 | Event News
25.05.2018 | Event News
25.05.2018 | Machine Engineering
25.05.2018 | Life Sciences