Germline P Granules Are Liquid Droplets That Localize by Controlled Dissolution/Condensation

@article{Brangwynne2009GermlinePG,
  title={Germline P Granules Are Liquid Droplets That Localize by Controlled Dissolution/Condensation},
  author={Clifford P. Brangwynne and Christian R Eckmann and David S. Courson and Agata Rybarska and Carsten Hoege and J{\"o}bin Gharakhani and Frank J{\"u}licher and Anthony A. Hyman},
  journal={Science},
  year={2009},
  volume={324},
  pages={1729 - 1732}
}
In sexually reproducing organisms, embryos specify germ cells, which ultimately generate sperm and eggs. [] Key Result As with other liquids, P granules rapidly dissolved and condensed. Localization occurred by a biased increase in P granule condensation at the posterior. This process reflects a classic phase transition, in which polarity proteins vary the condensation point across the cell. Such phase transitions may represent a fundamental physicochemical mechanism for structuring the cytoplasm.
Cell Cytoplasm Compartmentalization: Localization Through Gradients
TLDR
Experimental evidence is presented which shows that P granules are liquid droplets, and that their localization occurs through preferential nucleation and growth behavior on one side of the cell and simultaneous preferential dissolution on the opposite side, and a theoretical model for the preferential growth of P granule is developed, which mimics the properties of the Mex-5 gradient.
P granules phase transition induced by cytoplasmic streaming in Caenorhabditis elegans embryo
TLDR
P granules, initially distributing uniformly in the entire one-cell embryo, eventually condense/dissolve in the cytoplasm phase, regulated by difference between the saturation pressure and the hydrodynamic pressure.
Perinuclear P granules are the principal sites of mRNA export in adult C. elegans germ cells
TLDR
The results suggest that nuclear-associated P granules provide a perinuclear compartment where newly exported mRNAs are collected prior to their release to the general cytoplasm, and show that mRNA export factors are highly enriched at the NPCs associated with P granule.
The Dynamics of P Granule Liquid Droplets Are Regulated by the Caenorhabditis elegans Germline RNA Helicase GLH-1 via Its ATP Hydrolysis Cycle
TLDR
Evidence is shown that the VASA-like germline RNA helicase GLH-1 couples distinct steps of its ATPase hydrolysis cycle to control the formation and disassembly of P granules, and defects in recruiting the P granule component PRG-1 to perinuclear foci in the adult germline correlate with the fertility defects observed in various GLh-1 mutants.
JCB: Report
TLDR
It is shown that the PGL proteins P GL­1 and PGL­3 serve as the scaffold for germ granule formation in Caenorhabditis elegans, and it is proposed that self­association of scaffold proteins that can bind to RNPs is a general mechanism by which large RNP granules are formed.
Cytoplasmic Partitioning of P Granule Components Is Not Required to Specify the Germline in C. elegans
TLDR
A Caenorhabditis elegans mutant is identified in which P granules become unstable during mitosis and P granule proteins and RNAs are distributed equally to somatic and germline blastomeres, suggesting that asymmetric partitioning of maternal Pgranules is not essential to specify germ cell fate and may serve to protect the nascent germline from stress.
P granule assembly and function in Caenorhabditis elegans germ cells.
TLDR
The findings in C elegans have important implications for the germ granule function during postnatal germ cell differentiation in mammals and the genetic pathway of P granule assembly is reviewed.
Membraneless organelles: P granules in Caenorhabditis elegans
TLDR
These findings from C elegans, combined with work done in other model organisms, continue to provide insight into the formation of membraneless organelles and the important role they play in compartmentalizing cellular processes.
Next generation organelles: Structure and role of germ granules in the germline
TLDR
Recent studies have shown that different somatic cells, including stem cells and neurons, produce germ granule components that play a crucial role in stem cell maintenance and memory formation, indicating a much more diverse functional repertoire for these organelles than previously thought.
A gel phase promotes condensation of liquid P granules in C. elegans embryos
TLDR
This work finds that the PGL-3 phase is intrinsically labile and requires a second phase for stabilization in embryos, and suggests that condensation of RNA granules can be regulated spatially by gel-like polymers that stimulate LLPS locally in the cytoplasm.
...
...

References

SHOWING 1-10 OF 23 REFERENCES
Segregation of germ granules in living Caenorhabditis elegans embryos: cell-type-specific mechanisms for cytoplasmic localisation.
TLDR
It is shown that, in early P cells (P0 and P1), P-granule partitioning is achieved primarily by their migration through the cytoplasm towards the site of formation of the germline daughter cell, where they are then deposited.
Control over the morphology and segregation of Zebrafish germ cell granules during embryonic development
TLDR
The results suggest that Zebrafish germ cell granules undergo a transformation process, which involves germ cell specific proteins as well as the microtubular network.
Cortical and cytoplasmic flow polarity in early embryonic cells of Caenorhabditis elegans
TLDR
A model for the events of PC is presented and how the poles of the mitotic spindle mediate the formation of the contractile ring during cytokinesis in C. elegans is suggested.
Exclusion of germ plasm proteins from somatic lineages by cullin-dependent degradation
TLDR
It is shown that five CCCH finger proteins, components of the Caenorhabditis elegans germ plasm, are targeted for degradation by the novel CCCH-finger-binding protein ZIF-1, a SOCS-box protein that interacts with the E3 ubiquitin ligase subunit elongin C.
Cell polarity and the cytoskeleton in the Caenorhabditis elegans zygote.
TLDR
Recent advances in understanding of the mechanisms that polarize the one-cell zygote to generate an AP axis of asymmetry are reviewed.
Multiple potential germ-line helicases are components of the germ-line-specific P granules of Caenorhabditis elegans.
TLDR
Two components of the germ-line-specific P granules of the nematode Caenorhabditis elgans have been identified using polyclonal antibodies specific for each, and it seems likely that they represent a fairly recent gene duplication event.
Polarization of the C. elegans zygote proceeds via distinct establishment and maintenance phases
TLDR
These studies reveal that polarization involves two genetically and temporally distinct phases, and provide a model for how PAR and MEX proteins convert a transient asymmetry into a stably polarized axis.
MEX-5 asymmetry in one-cell C. elegans embryos requires PAR-4- and PAR-1-dependent phosphorylation
TLDR
It is shown that PAR-1 and PAR-4 kinase activities are required for the phosphorylation of S458, providing a link between PAR polarity proteins and the cytoplasmic asymmetry of MEX-5, and that a crucial residue in the C-terminus, Ser 458, is phosphorylated in vivo.
...
...