Perinuclear P granules are the principal sites of mRNA export in adult C. elegans germ cells

P granules are cytoplasmic structures of unknown function that are associated with germ nuclei in the C. elegans gonad, and are localized exclusively to germ cells, or germ cell precursors, throughout the life cycle. All the known protein components of P granules contain putative RNA-binding motifs, suggesting that RNA is involved in either the structure or function of the granules. However, no specific mRNAs have been identified within P granules in the gonad. We show here that P granules normally contain a low level of RNA, and describe conditions that increase this level. We present evidence that several, diverse mRNAs, including pos-1, mex-1, par-3, skn-1, nos-2 and gld-1 mRNA, are present at least transiently within P granules. In contrast, actin and tubulin mRNA and rRNA are either not present in P granules, or are present at relatively low levels. We show that pgl-1 and the glh (Vasa-related) gene family, which encode protein components of P granules, do not appear essential for RNA to concentrate in P granules; these proteins may instead function in events that are a prerequisite for RNAs to be transported efficiently from the nuclear surface.

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Faculty Opinions recommendation of Analysis of RNA associated with P granules in germ cells of C. elegans adults.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1011362.179719 ◽

2003 ◽

Author(s):

Bruce Bowerman

Keyword(s):

Germ Cells ◽

P Granules ◽

C Elegans

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The C. elegans MEX-1 protein is present in germline blastomeres and is a P granule component

Development ◽

10.1242/dev.124.3.731 ◽

1997 ◽

Vol 124 (3) ◽

pp. 731-739 ◽

Cited By ~ 5

Author(s):

S. Guedes ◽

J.R. Priess

Keyword(s):

Germ Cells ◽

Gene Products ◽

Cytoplasmic Protein ◽

Embryonic Cells ◽

Nematode Caenorhabditis Elegans ◽

P Granules ◽

C Elegans ◽

Cytoplasmic Structures ◽

Fertilized Egg ◽

Expression And Activity

In the nematode Caenorhabditis elegans, germ cells arise from early embryonic cells called germline blastomeres. Cytoplasmic structures called P granules are present in the fertilized egg and are segregated into each of the germline blastomeres during the first few cleavages of the embryo. Mutations in the maternally expressed gene mex-1 disrupt the segregation of P granules, prevent the formation of germ cells, and cause inappropriate patterns of somatic cell differentiation. We have cloned the mex-1 gene and determined the distribution pattern of the mex-1 gene products. The MEX-1 protein contains two copies of an unusual ‘finger’ domain also found in the PIE-1 protein of C. elegans. PIE-1 has been shown to be expressed in germline blastomeres, and is a component of P granules. We show here that MEX-1 also is present in germline blastomeres and is a P granule component, although MEX-1 is a cytoplasmic protein while PIE-1 is present in both the nucleus and cytoplasm. We further show that MEX-1 is required to restrict PIE-1 expression and activity to the germline blastomeres during the early embryonic cleavages.

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P granules protect RNA interference genes from silencing by piRNAs

10.1101/707562 ◽

2019 ◽

Author(s):

John Paul T. Ouyang ◽

Andrew Folkmann ◽

Lauren Bernard ◽

Chih-Yung Lee ◽

Uri Seroussi ◽

...

Keyword(s):

Rna Interference ◽

Germ Cells ◽

Small Rnas ◽

Primordial Germ Cells ◽

Safe Harbor ◽

Wild Type ◽

P Granules ◽

C Elegans ◽

Rna Biogenesis ◽

Endogenous Genes

SUMMARYP granules are perinuclear condensates in C. elegans germ cells proposed to serve as hubs for self/non-self RNA discrimination by Argonautes. We report that a mutant (meg-3 meg-4) that does not assemble P granules in primordial germ cells loses competence for RNA-interference over several generations and accumulates silencing small RNAs against hundreds of endogenous genes, including the RNA-interference genes rde-11 and sid-1. In wild-type, rde-11 and sid-1 transcripts are heavily targeted by piRNAs, accumulate in P granules, but maintain expression. In the primordial germ cells of meg-3 meg-4 mutants, rde-11 and sid-1 transcripts disperse in the cytoplasm with the small RNA biogenesis machinery, become hyper-targeted by secondary sRNAs, and are eventually silenced. Silencing requires the PIWI-class Argonaute PRG-1 and the nuclear Argonaute HRDE-1 that maintains trans-generational silencing of piRNA targets. These observations support a “safe harbor” model for P granules in protecting germline transcripts from piRNA-initiated silencing.

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Faculty Opinions recommendation of C. elegans germ cells show temperature and age-dependent expression of Cer1, a Gypsy/Ty3-related retrotransposon.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.717197869.792452870 ◽

2012 ◽

Author(s):

Andrew Chisholm

Keyword(s):

Germ Cells ◽

C Elegans ◽

Age Dependent

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Faculty Opinions recommendation of P granules extend the nuclear pore complex environment in the C. elegans germ line.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.720058984.793512095 ◽

2015 ◽

Author(s):

Florence Marlow

Keyword(s):

Nuclear Pore Complex ◽

Germ Line ◽

Nuclear Pore ◽

Complex Environment ◽

P Granules ◽

C Elegans

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C. elegans germ granules require both assembly and localized regulators for mRNA repression

Nature Communications ◽

10.1038/s41467-021-21278-1 ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Scott Takeo Aoki ◽

Tina R. Lynch ◽

Sarah L. Crittenden ◽

Craig A. Bingman ◽

Marvin Wickens ◽

...

Keyword(s):

Liquid Droplet ◽

Scaffolding Protein ◽

P Granules ◽

C Elegans ◽

Cytoplasmic Rna ◽

And Function ◽

Rnp Granules ◽

Key Residues ◽

Reporter Mrna

AbstractCytoplasmic RNA–protein (RNP) granules have diverse biophysical properties, from liquid to solid, and play enigmatic roles in RNA metabolism. Nematode P granules are paradigmatic liquid droplet granules and central to germ cell development. Here we analyze a key P granule scaffolding protein, PGL-1, to investigate the functional relationship between P granule assembly and function. Using a protein–RNA tethering assay, we find that reporter mRNA expression is repressed when recruited to PGL-1. We determine the crystal structure of the PGL-1 N-terminal region to 1.5 Å, discover its dimerization, and identify key residues at the dimer interface. Mutations of those interface residues prevent P granule assembly in vivo, de-repress PGL-1 tethered mRNA, and reduce fertility. Therefore, PGL-1 dimerization lies at the heart of both P granule assembly and function. Finally, we identify the P granule-associated Argonaute WAGO-1 as crucial for repression of PGL-1 tethered mRNA. We conclude that P granule function requires both assembly and localized regulators.

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glp-3 Is Required for Mitosis and Meiosis in the Caenorhabditis elegans Germ Line

Genetics ◽

10.1093/genetics/145.1.111 ◽

1997 ◽

Vol 145 (1) ◽

pp. 111-121 ◽

Cited By ~ 1

Author(s):

Lisa C Kadyk ◽

Eric J Lambie ◽

Judith Kimble

Keyword(s):

Caenorhabditis Elegans ◽

Germ Cells ◽

Germ Line ◽

Stem Cell Population ◽

Phenotypic Characterization ◽

Loss Of Function ◽

Dapi Staining ◽

Cell Cycles ◽

C Elegans ◽

Mitosis And Meiosis

The germ line is the only tissue in Caenorhabditis elegans in which a stem cell population continues to divide mitotically throughout life; hence the cell cycles of the germ line and the soma are regulated differently. Here we report the genetic and phenotypic characterization of the glp-3 gene. In animals homozygous for each of five recessive loss-of-function alleles, germ cells in both hermaphrodites and males fail to progress through mitosis and meiosis, but somatic cells appear to divide normally. Germ cells in animals grown at 15° appear by DAPI staining to be uniformly arrested at the G2/M transition with <20 germ cells per gonad on average, suggesting a checkpoint-mediated arrest. In contrast, germ cells in mutant animals grown at 25° frequently proliferate slowly during adulthood, eventually forming small germ lines with several hundred germ cells. Nevertheless, cells in these small germ lines never undergo meiosis. Double mutant analysis with mutations in other genes affecting germ cell proliferation supports the idea that glp-3 may encode a gene product that is required for the mitotic and meiotic cell cycles in the C. elegans germ line.

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P granules extend the nuclear pore complex environment in the C. elegans germ line

The Journal of Cell Biology ◽

10.1083/jcb.201010104 ◽

2011 ◽

Vol 192 (6) ◽

pp. 939-948 ◽

Cited By ~ 125

Author(s):

Dustin L. Updike ◽

Stephanie J. Hachey ◽

Jeremy Kreher ◽

Susan Strome

Keyword(s):

Nuclear Pore Complex ◽

Germ Plasm ◽

Germ Line ◽

Hydrophobic Interactions ◽

Nuclear Periphery ◽

Size Exclusion ◽

Nuclear Pore ◽

Complex Environment ◽

P Granules ◽

C Elegans

The immortal and totipotent properties of the germ line depend on determinants within the germ plasm. A common characteristic of germ plasm across phyla is the presence of germ granules, including P granules in Caenorhabditis elegans, which are typically associated with the nuclear periphery. In C. elegans, nuclear pore complex (NPC)–like FG repeat domains are found in the VASA-related P-granule proteins GLH-1, GLH-2, and GLH-4 and other P-granule components. We demonstrate that P granules, like NPCs, are held together by weak hydrophobic interactions and establish a size-exclusion barrier. Our analysis of intestine-expressed proteins revealed that GLH-1 and its FG domain are not sufficient to form granules, but require factors like PGL-1 to nucleate the localized concentration of GLH proteins. GLH-1 is necessary but not sufficient for the perinuclear location of granules in the intestine. Our results suggest that P granules extend the NPC environment in the germ line and provide insights into the roles of the PGL and GLH family proteins.

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