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 More genes are active in high-performance maize
19.01.2018 | Rheinische Friedrich-Wilhelms-Universität Bonn

nachricht How plants see light
19.01.2018 | Albert-Ludwigs-Universität Freiburg im Breisgau

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Artificial agent designs quantum experiments

On the way to an intelligent laboratory, physicists from Innsbruck and Vienna present an artificial agent that autonomously designs quantum experiments. In initial experiments, the system has independently (re)discovered experimental techniques that are nowadays standard in modern quantum optical laboratories. This shows how machines could play a more creative role in research in the future.

We carry smartphones in our pockets, the streets are dotted with semi-autonomous cars, but in the research laboratory experiments are still being designed by...

Im Focus: Scientists decipher key principle behind reaction of metalloenzymes

So-called pre-distorted states accelerate photochemical reactions too

What enables electrons to be transferred swiftly, for example during photosynthesis? An interdisciplinary team of researchers has worked out the details of how...

Im Focus: The first precise measurement of a single molecule's effective charge

For the first time, scientists have precisely measured the effective electrical charge of a single molecule in solution. This fundamental insight of an SNSF Professor could also pave the way for future medical diagnostics.

Electrical charge is one of the key properties that allows molecules to interact. Life itself depends on this phenomenon: many biological processes involve...

Im Focus: Paradigm shift in Paris: Encouraging an holistic view of laser machining

At the JEC World Composite Show in Paris in March 2018, the Fraunhofer Institute for Laser Technology ILT will be focusing on the latest trends and innovations in laser machining of composites. Among other things, researchers at the booth shared with the Aachen Center for Integrative Lightweight Production (AZL) will demonstrate how lasers can be used for joining, structuring, cutting and drilling composite materials.

No other industry has attracted as much public attention to composite materials as the automotive industry, which along with the aerospace industry is a driver...

Im Focus: Room-temperature multiferroic thin films and their properties

Scientists at Tokyo Institute of Technology (Tokyo Tech) and Tohoku University have developed high-quality GFO epitaxial films and systematically investigated their ferroelectric and ferromagnetic properties. They also demonstrated the room-temperature magnetocapacitance effects of these GFO thin films.

Multiferroic materials show magnetically driven ferroelectricity. They are attracting increasing attention because of their fascinating properties such as...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

10th International Symposium: “Advanced Battery Power – Kraftwerk Batterie” Münster, 10-11 April 2018

08.01.2018 | Event News

See, understand and experience the work of the future

11.12.2017 | Event News

Innovative strategies to tackle parasitic worms

08.12.2017 | Event News

 
Latest News

Let the good tubes roll

19.01.2018 | Materials Sciences

How cancer metastasis happens: Researchers reveal a key mechanism

19.01.2018 | Health and Medicine

Meteoritic stardust unlocks timing of supernova dust formation

19.01.2018 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>