Phase transitioned nuclear Oskar promotes cell division of Drosophila primordial germ cells

Germ granules are non-membranous ribonucleoprotein granules deemed the hubs for post-transcriptional gene regulation and functionally linked to germ cell fate across species. Little is known about the physical properties of germ granules and how these relate to germ cell function. Here we study two types of germ granules in the Drosophila embryo: cytoplasmic germ granules that instruct primordial germ cells (PGCs) formation and nuclear germ granules within early PGCs with unknown function. We show that cytoplasmic and nuclear germ granules are phase transitioned condensates nucleated by Oskar protein that display liquid as well as hydrogel-like properties. Focusing on nuclear granules, we find that Oskar drives their formation in heterologous cell systems. Multiple, independent Oskar protein domains synergize to promote granule phase separation. Deletion of Oskar’s nuclear localization sequence specifically ablates nuclear granules in cell systems. In the embryo, nuclear germ granules promote germ cell divisions thereby increasing PGC number for the next generation.

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Phase Transitioned Nuclear Oskar Promotes Cell Division of Drosophila Primordial Germ Cells

10.1101/397992 ◽

2018 ◽

Cited By ~ 1

Author(s):

Kathryn E. Kistler ◽

Tatjana Trcek ◽

Thomas R. Hurd ◽

Ruoyu Chen ◽

Feng-Xia Liang ◽

...

Keyword(s):

Germ Cell ◽

Cell Fate ◽

Germ Cells ◽

Cell Function ◽

Primordial Germ Cells ◽

Nuclear Localization Sequence ◽

Cell Systems ◽

Germ Granules ◽

Localization Sequence ◽

Transcriptional Gene Regulation

ABSTRACTGerm granules are non-membranous ribonucleoprotein granules deemed the hubs for post-transcriptional gene regulation and functionally linked to germ cell fate across species. Little is known about the physical properties of germ granules and how these relate to germ cell function. Here we study two types of germ granules in the Drosophila embryo: cytoplasmic germ granules that instruct primordial germ cells (PGCs) formation and nuclear germ granules within early PGCs with unknown function. We show that cytoplasmic and nuclear germ granules are phase transitioned condensates nucleated by Oskar protein that display liquid as well as hydrogel-like properties. Focusing on nuclear granules, we find that Oskar drives their formation in heterologous cell systems. Multiple, independent Oskar protein domains synergize to promote granule phase separation. Deletion of Oskar’s nuclear localization sequence specifically ablates nuclear granules in cell systems. In the embryo, nuclear germ granules promote germ cell divisions thereby increasing PGC number for the next generation.

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Distribution of tudor protein in the Drosophila embryo suggests separation of functions based on site of localization

Development ◽

10.1242/dev.119.1.207 ◽

1993 ◽

Vol 119 (1) ◽

pp. 207-219 ◽

Cited By ~ 12

Author(s):

A. Bardsley ◽

K. McDonald ◽

R.E. Boswell

Keyword(s):

Germ Cell ◽

Germ Cells ◽

Germ Plasm ◽

Primordial Germ Cells ◽

Posterior Pole ◽

Drosophila Embryo ◽

Normal Functioning ◽

Polar Granules ◽

Pole Cells

Mutations in the tudor locus of Drosophila affect two distinct determinative processes in embryogenesis; segmentation of the abdomen and determination of the primordial germ cells. The distribution of tudor protein during embryogenesis, and the effect of various mutations on its distribution, suggest that tudor protein may carry out these functions separately, based on its location in the embryo. The protein is concentrated in the posterior pole cytoplasm (germ plasm), where it is found in polar granules and mitochondria. Throughout the rest of the embryo, tudor protein is associated with the cleavage nuclei. Mutations in all maternal genes known to be required for the normal functioning of the germ plasm eliminate the posterior localization of tudor protein, whereas mutations in genes required for the functioning of the abdominal determinant disrupt the localization around nuclei. Analysis of embryos of different maternal genotypes indicates that the average number of pole cells formed is correlated with the amount of tudor protein that accumulates in the germ plasm. Our results suggest that tudor protein localized in the germ plasm is instrumental in germ cell determination, whereas nuclear-associated tudor protein is involved in determination of segmental pattern in the abdomen.

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Extensive nuclear gyration and pervasive non-genic transcription during primordial germ cell development in zebrafish

Development ◽

10.1242/dev.193060 ◽

2020 ◽

pp. dev.193060

Author(s):

Stefan Redl ◽

Antonio M. de Jesus Domingues ◽

Edoardo Caspani ◽

Stefanie Möckel ◽

Willi Salvenmoser ◽

...

Keyword(s):

Germ Cell ◽

Cell Fate ◽

Germ Cells ◽

Primordial Germ Cells ◽

Primordial Germ Cell ◽

Genital Ridge ◽

Non Coding Rna ◽

Pathway Activation ◽

Pirna Pathway ◽

Time Point

Primordial germ cells (PGCs) are the precursors of germ cells, which migrate to the genital ridge during early development. Relatively little is known about PGCs after their migration. We studied this post-migratory stage using microscopy and sequencing techniques, and found that many PGC-specific genes, including genes known to induce PGC fate in the mouse, are only activated several days after migration. At this same time point, PGC nuclei become extremely gyrated, displaying general broad opening of chromatin and high levels of intergenic transcription. This is accompanied by changes in nuage morphology, expression of large loci (PGC-Expressed non-coding RNA Loci, PERLs) that are enriched for retro-transposons and piRNAs, and a rise in piRNA biogenesis signatures. Interestingly, no nuclear Piwi protein could be detected at any time point, indicating that the zebrafish piRNA pathway is fully cytoplasmic. Our data show that the post-migratory stage of zebrafish PGCs holds many cues to both germ cell fate establishment and piRNA pathway activation.

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Germ granules prevent accumulation of somatic transcripts in the adult C. elegans germline

10.1101/089433 ◽

2016 ◽

Author(s):

Andrew Kekūpa’a Knutson ◽

Thea Egelhofer ◽

Andreas Rechtsteiner ◽

Susan Strome

Keyword(s):

Germ Cell ◽

Cell Fate ◽

Single Molecule ◽

Germ Cells ◽

Neuronal Development ◽

Developmental Stages ◽

Developmental Potential ◽

P Granules ◽

Germ Granules ◽

Rna Accumulation

ABSTRACTThe germ cells of multicellular organisms protect their developmental potential through specialized mechanisms. A shared feature of germ cells from worms to humans is the presence of non-membrane-bound ribonucleoprotein organelles called germ granules. Depletion of germ granules in Caenorhabditis elegans (i.e., P granules) leads to sterility and in some germlines expression of the neuronal transgene unc-119::gfp and the muscle myosin MYO-3. Thus, P granules are hypothesized to maintain germ cell totipotency by preventing somatic development, although the mechanism by which P granules carry out this function is unknown. In this study, we performed transcriptome and single molecule RNA-FISH analyses of dissected P-granule-depleted gonads at different developmental stages. Our results demonstrate that P granules are necessary for adult germ cells to down-regulate spermatogenesis RNAs and to prevent the accumulation of numerous soma-specific RNAs. P-granule-depleted gonads that express the unc-119::gfp transgene also express many other genes involved in neuronal development and concomitantly lose expression of germ cell fate markers. Finally, we show that removal of either of two critical P-granule components, PGL-1 or GLH-1, is sufficient to cause germ cells to express UNC-119::GFP and MYO-3 and to display RNA accumulation defects similar to those observed after depletion of P granules. Our data identify P granules as critical modulators of the germline transcriptome and guardians of germ cell fate.

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Extensive nuclear gyration and pervasive non-genic transcription during primordial germ cell development in zebrafish

10.1101/2020.01.10.901306 ◽

2020 ◽

Author(s):

Stefan Redl ◽

Antonio M. de Jesus Domingues ◽

Stefanie Möckel ◽

Willi Salvenmoser ◽

Maria Mendez-Lago ◽

...

Keyword(s):

Germ Cell ◽

Cell Fate ◽

Early Development ◽

Germ Cells ◽

Primordial Germ Cells ◽

Primordial Germ Cell ◽

Piwi Protein ◽

Genital Ridge ◽

Pathway Activation ◽

Pirna Pathway

SUMMARYPrimordial germ cells (PGCs) are the precursors of germ cells, which migrate to the genital ridge during early development. Relatively little is known about PGCs after their migration. We studied this post-migratory stage using microscopy and sequencing techniques, and found that many PGC-specific genes, including genes known to induce PGC fate in the mouse, are only activated several days after migration. At this same timepoint, PGC nuclei become extremely gyrated, displaying general opening of chromatin and high levels of transcription. This is accompanied by changes in nuage morphology, expression of large loci, named PERLs, enriched for retro-transposons and piRNAs, and a rise in piRNA biogenesis signatures. Interestingly, no nuclear Piwi protein could be detected at any timepoint, indicating that the zebrafish piRNA pathway is fully cytoplasmic. Our data show that the post-migratory stage of zebrafish PGCs holds many cues to both germ cell fate establishment and piRNA pathway activation.

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Specification of germ cell fate in mice

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2003.1324 ◽

2003 ◽

Vol 358 (1436) ◽

pp. 1363-1370 ◽

Cited By ~ 53

Author(s):

Mitinori Saitou ◽

Bernhard Payer ◽

Ulrike C. Lange ◽

Sylvia Erhardt ◽

Sheila C. Barton ◽

...

Keyword(s):

Germ Cell ◽

Cell Fate ◽

Germ Cells ◽

Transcriptional Repression ◽

Single Cell Analysis ◽

Primordial Germ Cells ◽

Cell Specification ◽

Signalling Molecules ◽

Germ Cell Specification

An early fundamental event during development is the segregation of germ cells from somatic cells. In many organisms, this is accomplished by the inheritance of preformed germ plasm, which apparently imposes transcriptional repression to prevent somatic cell fate. However, in mammals, pluripotent epiblast cells acquire germ cell fate in response to signalling molecules. We have used single cell analysis to study how epiblast cells acquire germ cell competence and undergo specification. Germ cell competent cells express Fragilis and initially progress towards a somatic mesodermal fate. However, a subset of these cells, the future primordial germ cells (PGCs), then shows rapid upregulation of Fragilis with concomitant transcriptional repression of a number of genes, including Hox and Smad genes. This repression may be a key event associated with germ cell specification. Furthermore, PGCs express Stella and other genes, such as Oct – 4 that are associated with pluripotency. While these molecules are also detected in mature oocytes as maternally inherited factors, their early role is to regulate development and maintain pluripotency, and they do not serve the role of classical germline determinants.

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Induction of Primordial Germ Cells from Pluripotent Epiblast

The Scientific World JOURNAL ◽

10.1100/tsw.2002.155 ◽

2002 ◽

Vol 2 ◽

pp. 801-810 ◽

Cited By ~ 13

Author(s):

Ying Ying ◽

Xiaoxia Qi ◽

Guang-Quan Zhao

Keyword(s):

Germ Cell ◽

Cell Fate ◽

Bone Morphogenetic Proteins ◽

Germ Cells ◽

Primordial Germ Cells ◽

Cell Lineage ◽

Close Relative ◽

Cell Fate Specification ◽

Visceral Endoderm ◽

Receptor Complexes

The formation of germ cells during embryogenesis bears the ultimate importance for the continuation of every species. It becomes evident that mechanisms governing germ cell fate specification are not well conserved across the animal kingdom. In most of the invertebrate and nonmammalian vertebrate species, certain maternally derived factors are key to the establishment of germ cell lineage. In contrast, mouse primordial germ cells (PGCs) are induced from the pluripotent epiblast cells before and during gastrulation by the extraembryonic cell-derived signals. The molecular identity for some of these signals has recently been revealed by genetic and epiblast culture experiments. Both bone morphogenetic proteins 4 (Bmp4) and 8b (Bmp8b) are expressed in the extraembryonic ectoderm and are required for PGC formation. Furthermore, BMP4 or BMP8B alone are unable to induce PGCs from cultured epiblasts, while they can in combination, indicating they signal through separate receptor complexes. In addition, Bmp4 homozygous embryos cannot be induced to form PGCs by the synergistic action of BMP4 and BMP8B, suggesting that BMP4 proteins produced by pregastrula embryos are required for epiblast cells to maintain pluripotency. Moreover, Bmp2, a close relative of Bmp4, is expressed in visceral endoderm at the time of PGC specification, and inactivation of Bmp2 results in a reduction in PGC number, revealing a novel function of visceral endoderm in PGC generation in the mouse.

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Ligand–Receptor Interactions Elucidate Sex-Specific Pathways in the Trajectory From Primordial Germ Cells to Gonia During Human Development

Frontiers in Cell and Developmental Biology ◽

10.3389/fcell.2021.661243 ◽

2021 ◽

Vol 9 ◽

Author(s):

Arend W. Overeem ◽

Yolanda W. Chang ◽

Jeroen Spruit ◽

Celine M. Roelse ◽

Susana M. Chuva De Sousa Lopes

Keyword(s):

Germ Cell ◽

Signaling Pathways ◽

Germ Cells ◽

Tyrosine Kinases ◽

Intracellular Localization ◽

Primordial Germ Cells ◽

Cell Lineage ◽

Systematic Analysis ◽

Receptor Interactions

The human germ cell lineage originates from primordial germ cells (PGCs), which are specified at approximately the third week of development. Our understanding of the signaling pathways that control this event has significantly increased in recent years and that has enabled the generation of PGC-like cells (PGCLCs) from pluripotent stem cells in vitro. However, the signaling pathways that drive the transition of PGCs into gonia (prospermatogonia in males or premeiotic oogonia in females) remain unclear, and we are presently unable to mimic this step in vitro in the absence of gonadal tissue. Therefore, we have analyzed single-cell transcriptomics data of human fetal gonads to map the molecular interactions during the sex-specific transition from PGCs to gonia. The CellPhoneDB algorithm was used to identify significant ligand–receptor interactions between germ cells and their sex-specific neighboring gonadal somatic cells, focusing on four major signaling pathways WNT, NOTCH, TGFβ/BMP, and receptor tyrosine kinases (RTK). Subsequently, the expression and intracellular localization of key effectors for these pathways were validated in human fetal gonads by immunostaining. This approach provided a systematic analysis of the signaling environment in developing human gonads and revealed sex-specific signaling pathways during human premeiotic germ cell development. This work serves as a foundation to understand the transition from PGCs to premeiotic oogonia or prospermatogonia and identifies sex-specific signaling pathways that are of interest in the step-by-step reconstitution of human gametogenesis in vitro.

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Genetic control of programmed cell death in the Caenorhabditis elegans hermaphrodite germline

Development ◽

10.1242/dev.126.5.1011 ◽

1999 ◽

Vol 126 (5) ◽

pp. 1011-1022 ◽

Cited By ~ 8

Author(s):

T.L. Gumienny ◽

E. Lambie ◽

E. Hartwieg ◽

H.R. Horvitz ◽

M.O. Hengartner

Keyword(s):

Cell Death ◽

Caenorhabditis Elegans ◽

Germ Cell ◽

Somatic Cell ◽

Cell Fate ◽

Germ Cells ◽

Mapk Pathway ◽

Apoptotic Cell ◽

C Elegans ◽

Pathway Activation

Development of the nematode Caenorhabditis elegans is highly reproducible and the fate of every somatic cell has been reported. We describe here a previously uncharacterized cell fate in C. elegans: we show that germ cells, which in hermaphrodites can differentiate into sperm and oocytes, also undergo apoptotic cell death. In adult hermaphrodites, over 300 germ cells die, using the same apoptotic execution machinery (ced-3, ced-4 and ced-9) as the previously described 131 somatic cell deaths. However, this machinery is activated by a distinct pathway, as loss of egl-1 function, which inhibits somatic cell death, does not affect germ cell apoptosis. Germ cell death requires ras/MAPK pathway activation and is used to maintain germline homeostasis. We suggest that apoptosis eliminates excess germ cells that acted as nurse cells to provide cytoplasmic components to maturing oocytes.

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