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

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

eLife ◽

10.7554/elife.37949 ◽

2018 ◽

Vol 7 ◽

Cited By ~ 23

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 ◽

Drosophila Embryo ◽

Nuclear Localization Sequence ◽

Cell Systems ◽

Germ Granules ◽

Localization Sequence

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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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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Germ cell fate and seminiferous tubule development in bovine testis xenografts

Reproduction ◽

10.1530/rep.1.00912 ◽

2005 ◽

Vol 130 (6) ◽

pp. 923-929 ◽

Cited By ~ 54

Author(s):

Rahul Rathi ◽

Ali Honaramooz ◽

Wenxian Zeng ◽

Stefan Schlatt ◽

Ina Dobrinski

Keyword(s):

Germ Cell ◽

Cell Fate ◽

Germ Cells ◽

Cell Number ◽

Sperm Production ◽

Continuous Increase ◽

Control Tissue ◽

Low Efficiency ◽

Pachytene Spermatocytes ◽

Testis Tissue

Spermatogenesis can occur in testis tissue from immature bulls ectopically grafted into mouse hosts; however, efficiency of sperm production is lower than in other donor species. To elucidate a possible mechanism for the impaired spermatogenesis in bovine testis xenografts, germ cell fate and xenograft development were investigated at different time points and compared with testis tissue from age-matched calves as controls. Histologically, an initial decrease in germ cell number was noticed in xenografts recovered up to 2 months post-grafting without an increase in germ cell apoptosis. From 2 months onward, the number of germ cells increased. In contrast, a continuous increase in germ cell number was seen in control tissue. Pachytene spermatocytes were observed in some grafts before 4 months, whereas in the control tissue they were not present until 5 months of age. Beyond 4 months post-grafting spermatogenesis appeared to be arrested at the pachytene spermatocyte stage in most grafts. Elongated spermatids were observed between 6 and 8 months post-grafting, similar to the controls, albeit in much lower numbers. Lumen formation started earlier in grafts compared with controls and by 6 months post-grafting tubules with extensively dilated lumen were observed. A donor effect on efficiency of spermatogenesis was also observed. These results indicate that the low efficiency of sperm production in bovine xenografts is due to an initial deficit of germ cells and impaired meiotic and post-meiotic differentiation. The characterization of spermatogenic efficiency will provide the basis to understand the control of spermatogenesis in testis grafts.

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Expression Profiling of Mammalian Male Meiosis and Gametogenesis Identifies Novel Candidate Genes for Roles in the Regulation of Fertility

Molecular Biology of the Cell ◽

10.1091/mbc.e03-10-0762 ◽

2004 ◽

Vol 15 (3) ◽

pp. 1031-1043 ◽

Cited By ~ 97

Author(s):

Ulrich Schlecht ◽

Philippe Demougin ◽

Reinhold Koch ◽

Leandro Hermida ◽

Christa Wiederkehr ◽

...

Keyword(s):

Germ Cell ◽

Germ Cells ◽

Expression Profiling ◽

Large Scale ◽

Developmental Stages ◽

Expression Patterns ◽

Control Cell ◽

Cell Types ◽

Male Meiosis ◽

Cell Expression

We report a comprehensive large-scale expression profiling analysis of mammalian male germ cells undergoing mitotic growth, meiosis, and gametogenesis by using high-density oligonucleotide microarrays and highly enriched cell populations. Among 11,955 rat loci investigated, 1268 were identified as differentially transcribed in germ cells at subsequent developmental stages compared with total testis, somatic Sertoli cells as well as brain and skeletal muscle controls. The loci were organized into four expression clusters that correspond to somatic, mitotic, meiotic, and postmeiotic cell types. This work provides information about expression patterns of ∼200 genes known to be important during male germ cell development. Approximately 40 of those are included in a group of 121 transcripts for which we report germ cell expression and lack of transcription in three somatic control cell types. Moreover, we demonstrate the testicular expression and transcriptional induction in mitotic, meiotic, and/or postmeiotic germ cells of 293 as yet uncharacterized transcripts, some of which are likely to encode factors involved in spermatogenesis and fertility. This group also contains potential germ cell-specific targets for innovative contraceptives. A graphical display of the data is conveniently accessible through the GermOnline database at http://www.germonline.org .

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The fog-3 gene and regulation of cell fate in the germ line of Caenorhabditis elegans.

Genetics ◽

10.1093/genetics/139.2.561 ◽

1995 ◽

Vol 139 (2) ◽

pp. 561-577 ◽

Cited By ~ 4

Author(s):

R E Ellis ◽

J Kimble

Keyword(s):

Caenorhabditis Elegans ◽

Germ Cell ◽

Sexual Identity ◽

Cell Fate ◽

Germ Cells ◽

Regulatory Network ◽

Germ Line ◽

The Other ◽

Nematode Caenorhabditis Elegans ◽

Inhibitory Interactions

Abstract In the nematode Caenorhabditis elegans, germ cells normally adopt one of three fates: mitosis, spermatogenesis or oogenesis. We have identified and characterized the gene fog-3, which is required for germ cells to differentiate as sperm rather than as oocytes. Analysis of double mutants suggests that fog-3 is absolutely required for spermatogenesis and acts at the end of the regulatory hierarchy controlling sex determination for the germ line. By contrast, mutations in fog-3 do not alter the sexual identity of other tissues. We also have characterized the null phenotype of fog-1, another gene required for spermatogenesis; we demonstrate that it too controls the sexual identity of germ cells but not of other tissues. Finally, we have studied the interaction of these two fog genes with gld-1, a gene required for germ cells to undergo oogenesis rather than mitosis. On the basis of these results, we propose that germ-cell fate might be controlled by a set of inhibitory interactions among genes that specify one of three fates: mitosis, spermatogenesis or oogenesis. Such a regulatory network would link the adoption of one germ-cell fate to the suppression of the other two.

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MES-1, a protein required for unequal divisions of the germline in early C. elegans embryos, resembles receptor tyrosine kinases and is localized to the boundary between the germline and gut cells

Development ◽

10.1242/dev.127.20.4419 ◽

2000 ◽

Vol 127 (20) ◽

pp. 4419-4431 ◽

Cited By ~ 4

Author(s):

L.A. Berkowitz ◽

S. Strome

Keyword(s):

Cell Fate ◽

Tyrosine Kinases ◽

Spatial Organization ◽

Function Analysis ◽

Primordial Germ Cell ◽

P Granules ◽

C Elegans ◽

Autonomous Function ◽

Germ Granules ◽

A Cell

During Caenorhabditis elegans embryogenesis the primordial germ cell, P(4), is generated via a series of unequal divisions. These divisions produce germline blastomeres (P(1), P(2), P(3), P(4)) that differ from their somatic sisters in their size, fate and cytoplasmic content (e.g. germ granules). mes-1 mutant embryos display the striking phenotype of transformation of P(4) into a muscle precursor, like its somatic sister. A loss of polarity in P(2) and P(3) cell-specific events underlies the Mes-1 phenotype. In mes-1 embryos, P(2) and P(3) undergo symmetric divisions and partition germ granules to both daughters. This paper shows that mes-1 encodes a receptor tyrosine kinase-like protein, though it lacks several residues conserved in all kinases and therefore is predicted not to have kinase activity. Immunolocalization analysis shows that MES-1 is present in four- to 24-cell embryos, where it is localized in a crescent at the junction between the germline cell and its neighboring gut cell. This is the region of P(2) and P(3) to which the spindle and P granules must move to ensure normal division asymmetry and cytoplasmic partitioning. Indeed, during early stages of mitosis in P(2) and P(3), one centrosome is positioned adjacent to the MES-1 crescent. Staining of isolated blastomeres demonstrated that MES-1 was present in the membrane of the germline blastomeres, consistent with a cell-autonomous function. Analysis of MES-1 distribution in various cell-fate and patterning mutants suggests that its localization is not dependent on the correct fate of either the germline or the gut blastomere but is dependent upon correct spatial organization of the embryo. Our results suggest that MES-1 directly positions the developing mitotic spindle and its associated P granules within P(2) and P(3), or provides an orientation signal for P(2)- and P(3)-specific events.

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A sex-specific number of germ cells in embryonic gonads of Drosophila

Development ◽

10.1242/dev.121.6.1867 ◽

1995 ◽

Vol 121 (6) ◽

pp. 1867-1873 ◽

Cited By ~ 4

Author(s):

M. Poirie ◽

E. Niederer ◽

M. Steinmann-Zwicky

Keyword(s):

Germ Cell ◽

Germ Cells ◽

Developmental Stages ◽

Control Mechanism ◽

Cell Number ◽

Male And Female ◽

First Instar ◽

Specific Number ◽

Specific Control ◽

Time Point

Male first instar larvae possess more germ cells in their gonads than female larvae of the same stage. To determine the earliest time point of sexual dimorphism in germ cell number, we have counted the germ cells of sexed embryos at different developmental stages. We found no difference in germ cell number of male and female embryos at the blastoderm and early gastrulation stage, or when germ cells are about to exit the midgut pocket. We find, however, that males have significantly more germ cells than females as soon as the germ cells are near the places where the gonads are formed and in all later stages. Our results show that germ cells are subject to a sex-specific control mechanism that regulates the number of germ cells already in embryos.

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The H3K9 methyltransferase SETDB1 maintains female identity in Drosophila germ cells by repressing expression of key spermatogenesis genes

10.1101/259473 ◽

2018 ◽

Author(s):

Anne E. Smolko ◽

Laura Shapiro-Kulnane ◽

Helen K. Salz

Keyword(s):

Germ Cell ◽

Cell Fate ◽

Germ Cells ◽

Target Genes ◽

Female Identity ◽

Binding Partner ◽

Regional Deposition ◽

Female Specific ◽

Inappropriate Expression ◽

Novel Model

AbstractThe preservation of germ cell sexual identity is essential for gametogenesis. Here we show that H3K9me3-mediated gene silencing is integral to female fate maintenance in Drosophila germ cells. Germ cell-specific loss of the H3K9me3 pathway members, the trimethyltransferase SETDB1, its binding partner WDE, and the H3K9 binding protein HP1a, cause the inappropriate expression of testis genes. SETDB1 is required for H3K9me3 accumulation on a select subset of the silenced testis genes. Interestingly, these SETDB1-dependent H3K9me3 domains are highly localized and do not spread into neighboring loci. Regional deposition is especially striking at the phf7 locus, a key regulator of male germ cell sexual fate. phf7 is primarily regulated by alternative promoter usage and transcription start site (TSS) selection. We find H3K9me3 accumulation is restricted to the silenced testis-specific TSS region in ovaries. Furthermore, its recruitment to phf7 and repression of the testis-specific transcript is dependent on the female sex determination gene Sxl. These findings demonstrate that female identity is secured by a pathway in which Sxl is the upstream female-specific regulator, SETDB1 is the required chromatin writer and phf7 is one of the critical SETDB1 target genes. This function of SETDB1 is unrelated to its canonical role in piRNA biogenesis and silencing of transposable elements. Collectively our findings support a novel model in which female fate is preserved by deposition of H3K9me3 repressive marks on key spermatogenesis genes and suggest that this strategy for securing cell fate may be widespread.

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Germline sexual fate is determined by the antagonistic action of dmrt1 and foxl3/foxl2 in tilapia

Development ◽

10.1242/dev.199380 ◽

2021 ◽

pp. dev.199380

Author(s):

Shengfei Dai ◽

Shuangshuang Qi ◽

Xueyan Wei ◽

Xingyong Liu ◽

Yibing Li ◽

...

Keyword(s):

Environmental Factors ◽

Germ Cell ◽

Somatic Cell ◽

Cell Fate ◽

Germ Cells ◽

Sex Reversal ◽

Testicular Development ◽

Antagonistic Action ◽

Male And Female ◽

Fate Decision

Germline sexual fate has long been believed to be determined by the somatic environment, but this idea is challenged by recent studies of foxl3 mutants in medaka. Here we demonstrate that the sexual fate of tilapia germline is determined by the antagonistic interaction of dmrt1 and foxl3, which are transcriptionally repressed in male and female germ cells, respectively. Loss of dmrt1 rescued the germ cell sex reversal in foxl3Δ7/Δ7 XX fish, and loss of foxl3 partially rescued germ cell sex reversal but not somatic cell fate in dmrt1Δ5/Δ5 XY fish. Interestingly, germ cells lost sexual plasticity in dmrt1Δ5/Δ5 XY and foxl3Δ7/Δ7 XX single mutants, as aromatase inhibitor and estrogen treatment failed to rescue the respective phenotypes. However, recovery of germ cell sexual plasticity was observed in dmrt1/foxl3 double mutants. Importantly, mutation of somatic cell specific foxl2 resulted in testicular development in foxl3Δ7/Δ7 or dmrt1Δ5/Δ5 mutants. Our findings demonstrate that sexual plasticity of germ cells relies on the presence of both dmrt1 and foxl3. The existence of dmrt1 and foxl3 allows environmental factors to influence the sex fate decision in vertebrates.

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