Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Counting the molecules that pull cells apart


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 First time-lapse footage of cell activity during limb regeneration
25.10.2016 | eLife

nachricht Phenotype at the push of a button
25.10.2016 | Institut für Pflanzenbiochemie

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

Im Focus: Diamonds aren't forever: Sandia, Harvard team create first quantum computer bridge

By forcefully embedding two silicon atoms in a diamond matrix, Sandia researchers have demonstrated for the first time on a single chip all the components needed to create a quantum bridge to link quantum computers together.

"People have already built small quantum computers," says Sandia researcher Ryan Camacho. "Maybe the first useful one won't be a single giant quantum computer...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Ice shelf vibrations cause unusual waves in Antarctic atmosphere

25.10.2016 | Earth Sciences

Fluorescent holography: Upending the world of biological imaging

25.10.2016 | Power and Electrical Engineering

Etching Microstructures with Lasers

25.10.2016 | Process Engineering

More VideoLinks >>>