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!
Scientists discover species of dolphin that existed along South Carolina coast
24.08.2017 | New York Institute of Technology
The science of fluoride flipping
24.08.2017 | University of North Carolina Health Care
Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.
As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...
Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.
Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...
For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.
While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...
An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.
The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...
A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.
Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...
16.08.2017 | Event News
04.08.2017 | Event News
26.07.2017 | Event News
24.08.2017 | Life Sciences
24.08.2017 | Life Sciences
24.08.2017 | Medical Engineering