Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Counting the molecules that pull cells apart

25.07.2003


Scientists at the MPI-CBG in Dresden and EMBL in Heidelberg map forces that help cells divide

"Cells obey the laws of physics and chemistry," begins a famous biology textbook, and one of the main goals of molecular biology is to link the properties of single molecules to the behavior of cells and the lives of organisms. So it is probably no surprise that an important new discovery about the physical forces that underlie cell division comes from a physics student-turned biologist, using math and a laser "scalpel" integrated into a microscope. The findings appear in the current issue of the journal Science.

Stephan Grill, Joe Howard, Erik Schäffer, Ernst Stelzer and Tony Hyman - in a collaboration between the Max-Planck Institute of Molecular Cell Biology and Genetics in Dresden and EMBL in Heidelberg - have done something few scientists have managed: they have counted the number of proteins that help an egg cell divide. This initial division happens in a special way in the roundworm C. elegans, one of biology´s most important model organisms.



"The fertilized egg splits into one large and one smaller cell," Grill says. "That difference in size is crucial to the development of the whole roundworm body. Normally people think of cells as dividing into two identical daughters; if they don´t, there must be forces at work that create an imbalance. We wanted to map them."

As a PhD student at EMBL, working between the research groups of Tony Hyman and biophysicist/microscopist Ernst Stelzer, Grill pursued an intriguing lead. A cable-like network of proteins called microtubules tows freshly-copied DNA off to opposing sides of the cell. The identical sets of genetic material are then sealed off in their own cells. Normally the anchors that the tow-lines are attached to, called centrosomes, remain near the center of the cell. But in the roundworm egg, one centrosome wanders off towards the outer rim of the cell. Either it was being pulled there or pushed there, Grill reasoned, so he began zapping parts of the cell with a laser, trying to disrupt the mechanism.

Grill followed Hyman – and the laser microscope – to Dresden, maintaining the collaboration with Stelzer. In the latest round of experiments, he used the laser to punch a hole in the core of the centrosome. As the structure disintegrated, he tracked what happened to the fragments. By measuring the rate at which they drifted apart, he could put exact numbers on the forces pulling them.
"The `force-generators´ are molecules called motors; their job is to pull cargoes down microtubules," Grill says. "Here they pull on the centrosome to position it. We thought that there might be more motors on one side, or stronger motors, which would create a stronger pull. But we couldn´t distinguish whether that was the case."."

At this point, Joe Howard came into play, Grill says. "He just looked at the data, and suggested that we should look at the variance in the speed of the fragments from experiment to experiment. This was possible because we had performed a large enough number of experiments for a thorough statistical analysis." The differences that they observed displayed an intriguing feature that the scientists could submit to a mathematical analysis. They learned that there are more motors pulling on the posterior centrosome: about 25, compared to roughly 15 on the other side. Even though a small number of motors are involved, it is sufficient to to pull the centrosome off-center. This has dramatic consequences – it permits the proper development of the body of the embryo.

The measurements will now permit Grill and his colleagues to understand how other molecules change cellular forces and influence cell division. They have already shown that a signal passed along by the protein G-alpha is necessary to activate motors and pull the centrosome off-center.

"Cell division is a very complex process, whether the result is identical daughters or asymmetric ones," Grill says. "Having precise numbers will let us fine-tune the mathematical models and use them to look for molecules that help orchestrate this process in many other types of cells."

Russ Hodge | EurekAlert!

More articles from Life Sciences:

nachricht Glycosylation: Mapping Uncharted Territory
21.09.2017 | IMBA - Institut für Molekulare Biotechnologie der Österreichischen Akademie der Wissenschaften GmbH

nachricht Molecular Force Sensors
20.09.2017 | Max-Planck-Institut für Biochemie

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Highly precise wiring in the Cerebral Cortex

Our brains house extremely complex neuronal circuits, whose detailed structures are still largely unknown. This is especially true for the so-called cerebral cortex of mammals, where among other things vision, thoughts or spatial orientation are being computed. Here the rules by which nerve cells are connected to each other are only partly understood. A team of scientists around Moritz Helmstaedter at the Frankfiurt Max Planck Institute for Brain Research and Helene Schmidt (Humboldt University in Berlin) have now discovered a surprisingly precise nerve cell connectivity pattern in the part of the cerebral cortex that is responsible for orienting the individual animal or human in space.

The researchers report online in Nature (Schmidt et al., 2017. Axonal synapse sorting in medial entorhinal cortex, DOI: 10.1038/nature24005) that synapses in...

Im Focus: Tiny lasers from a gallery of whispers

New technique promises tunable laser devices

Whispering gallery mode (WGM) resonators are used to make tiny micro-lasers, sensors, switches, routers and other devices. These tiny structures rely on a...

Im Focus: Ultrafast snapshots of relaxing electrons in solids

Using ultrafast flashes of laser and x-ray radiation, scientists at the Max Planck Institute of Quantum Optics (Garching, Germany) took snapshots of the briefest electron motion inside a solid material to date. The electron motion lasted only 750 billionths of the billionth of a second before it fainted, setting a new record of human capability to capture ultrafast processes inside solids!

When x-rays shine onto solid materials or large molecules, an electron is pushed away from its original place near the nucleus of the atom, leaving a hole...

Im Focus: Quantum Sensors Decipher Magnetic Ordering in a New Semiconducting Material

For the first time, physicists have successfully imaged spiral magnetic ordering in a multiferroic material. These materials are considered highly promising candidates for future data storage media. The researchers were able to prove their findings using unique quantum sensors that were developed at Basel University and that can analyze electromagnetic fields on the nanometer scale. The results – obtained by scientists from the University of Basel’s Department of Physics, the Swiss Nanoscience Institute, the University of Montpellier and several laboratories from University Paris-Saclay – were recently published in the journal Nature.

Multiferroics are materials that simultaneously react to electric and magnetic fields. These two properties are rarely found together, and their combined...

Im Focus: Fast, convenient & standardized: New lab innovation for automated tissue engineering & drug

MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems Holding GmbH about commercial use of a multi-well tissue plate for automated and reliable tissue engineering & drug testing.

MBM ScienceBridge GmbH successfully negotiated a license agreement between University Medical Center Göttingen (UMG) and the biotech company Tissue Systems...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

“Lasers in Composites Symposium” in Aachen – from Science to Application

19.09.2017 | Event News

I-ESA 2018 – Call for Papers

12.09.2017 | Event News

EMBO at Basel Life, a new conference on current and emerging life science research

06.09.2017 | Event News

 
Latest News

Glycosylation: Mapping Uncharted Territory

21.09.2017 | Life Sciences

Highly precise wiring in the Cerebral Cortex

21.09.2017 | Health and Medicine

Did marine sponges trigger the ‘Cambrian explosion’ through ‘ecosystem engineering’?

21.09.2017 | Earth Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>