The discovery, which was made during the 2008 Physiology course at the Marine Biological Laboratory (MBL), is reported in the May 21 early online edition of Science by Clifford P. Brangwynne and Anthony A. Hyman of the Max Planck Institute for Molecular Cell Biology and Genetics in Dresden, Germany, and their colleagues, including Frank Jülicher of the Max Planck Institute for the Physics of Complex Systems, also in Dresden.
Working with the worm C. elegans, the scientists found that subcellular structures called P granules, which are thought to specify the "germ cells" that ultimately give rise to sperm or eggs, are liquid droplets that transition between a dissolved or condensed state. In newly fertilized one-cell embryos, the P granules are dissolving throughout the cell, like water droplets at high temperature. But prior to the first cell division, the P granules rapidly condense at one end of the cell, as if the temperature were suddenly lowered there. The progenitor germ cell subsequently forms where the P granules have condensed.
"This kind of phase transition could potentially be working for many other subcellular structures similar to P granules," Brangwynne says. P granules are ribonucleoprotein assemblies (RNPs), and a given cell may contain dozens of different types of RNPs.
"It is interesting to think about this in the context of evolution and the origin of life," he says. "What we have found is that, in some cases, simple physical-chemical mechanisms, such as a classic phase transition, give rise to subcellular structure…This is likely the kind of thing that happened in the so-called primordial soup; but it's not surprising that even highly evolved cells continue to take advantage of such mechanisms."
The insight emerged when Brangwynne, a biophysicist who was a teaching assistant in the MBL Physiology course, watched a movie of P granules fusing that had been made by a student in the course, David Courson of the University of Chicago. "We were looking at that and thinking, man, that looks exactly like two liquid droplets fusing," Brangwynne says. They began making measurements of liquid-type behaviors in P granules, and made the first estimates of P granule viscosity and surface tension. By the end of the course they were "90 percent sure" that P granules are liquid droplets that localize in the cell by controlled dissolution and condensation, a concept that Brangwynne further confirmed after he returned to Dresden.
Brangwynne credits the discovery to the "dynamic nature" of the MBL Physiology course, where scientists from different fields (biology, physics, computer science) work intensively together on major research questions in cell biology. In addition to Courson, the other co-authors of the Science paper who were in the Physiology course are Hyman, and Jülicher, who were Physiology faculty members, and Jöbin Gharakhani, who was a teaching assistant. The paper also credits Physiology course co-director Tim Mitchison for valuable discussions.
"There are so many molecules in the cell, and we are coming out of the age of cataloguing them all, which was critical, to find out who the players are," Brangwynne says. "Now we are putting it all together. What are the principles that come out of these complex interactions (between molecules)? In the end, it may be relatively simple principles that help us understand what is really happening."
Brangwynne, C.P., Eckmann, C.R., Courson, D.S., Rybarska, A., Hoege, C., Gharakhani, J., Jülicher, F., and Hyman, A.A. (2009) Germline P Granules are Liquid Droplets that Localize by Controlled Dissolution/Condensation. Early publication online by the journal Science, at the Science Express web site: http://www.sciencexpress.org.
The MBL is a leading international, independent, nonprofit institution dedicated to discovery and to improving the human condition through creative research and education in the biological, biomedical and environmental sciences. Founded in 1888 as the Marine Biological Laboratory, the MBL is the oldest private marine laboratory in the Americas.
Diana Kenney | EurekAlert!
How brains surrender to sleep
23.06.2017 | IMP - Forschungsinstitut für Molekulare Pathologie GmbH
A new technique isolates neuronal activity during memory consolidation
22.06.2017 | Spanish National Research Council (CSIC)
An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.
Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...
Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.
Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...
Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.
As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...
Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.
With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...
Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine
Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...
19.06.2017 | Event News
13.06.2017 | Event News
13.06.2017 | Event News
23.06.2017 | Physics and Astronomy
23.06.2017 | Physics and Astronomy
23.06.2017 | Information Technology