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Divide and enlarge

Researchers discover a mechanism that causes cell nuclei to grow

Freiburg, Sep 22, 2020

Divide and enlarge

Two cell nuclei after division: At the top, fibers of actin are bundled with the aid of the protein Alpha-Actinin 4 (ACTN4) in the nucleus. Below, ACTN4 is inhibited or entirely absent. Illustration: Robert Grosse/Ulrike Endesfelder

By far the most important process in cell development is how cells divide and then enlarge in order to multiply. A research team headed by Freiburg medical scientist Prof. Dr. Robert Grosse has now discovered that bundled fibers of actin within a cell nucleus play an important part in how they enlarge after division. Fibers of the structural protein actin stabilize the outer form of the cell and transport substances into a cell. The mechanisms that influence the growth of the cell nucleus after division were less well known by scientists. The researchers have published their results in the journal 'EMBO reports'.

After dividing, cell nuclei have to grow in order to reorganize and unpack the genetic information in chromatin, the basic genetic material, and so process and read it. With this work the scientists show that bundled fibers of actin – which are normally responsible for exercising force – work within the cell to expand the nucleus. Using a video microscope the researchers have measured in living cells how cell nuclei enlarge immediately after division. In order to observe the fibers of actin and skeletal structures in the cell nucleus, they also used a high-resolution super-resolution microscope.

In the future Grosse and his team want to clarify whether mechanical forces work within the cell nucleus to re-organize them to sort the genetic information. If so, this process could for example be disrupted or changed in tumor cells or play a part in stem cells.

Freiburg medical scientist Robert Grosse is a professor of Pharmacology and Toxicology and director of Division I at the Institute of Experimental and Clinical Pharmacology and Toxicology, as well as a member of the Cluster of Excellence CIBSS – Centre for Integrative Biological Signalling Studies at the University of Freiburg. His team is working with a group headed by Dr. Ulrike Endesfelder from the Max Planck Institute for Terrestrial Microbiology in Marburg, which is contributing expertise in super-resolution microscopy.

Wilhelm Sander Foundation: Partner of innovative cancer research
The Wilhelm Sander Foundation supported this research project in two funding phases with around 270,000 euros. The purpose of the foundation is to promote medical research, in particular projects in the context of fighting cancer. Since the foundation was set up, a total of around 245 million euros has been spent for research funding in Germany and Switzerland. This makes the Wilhelm Sander Foundation one of the most important private research foundations in Germany. It was founded from the estate of the entrepreneur Wilhelm Sander, who died in 1973.


Original publication:

Krippner, S., Winkelmeier, J., Knerr, J., Brandt, D. T., Virant, D., Schwan, C., Endesfelder, U. & Grosse, R. (2020). Post-mitotic expansion of cell nuclei requires nuclear actin filament bundling by a-actinin 4. In EMBO reports, DOI: 10.15252/embr.202050758


Prof. Dr. Robert Grosse
Institute of Experimental and Clinical Pharmacology and Toxicology
University of Freiburg
Tel.: +49 761 203-5301


Graphic for download
Illustration: Robert Grosse/Ulrike Endesfelder