The Polycomb group in Caenorhabditis elegans and maternal control of germline development

Development ◽  
1998 ◽  
Vol 125 (13) ◽  
pp. 2469-2478 ◽  
Author(s):  
I. Korf ◽  
Y. Fan ◽  
S. Strome

Four Caenorhabditis elegans genes, mes-2, mes-3, mes-4 and mes-6, are essential for normal proliferation and viability of the germline. Mutations in these genes cause a maternal-effect sterile (i.e. mes) or grandchildless phenotype. We report that the mes-6 gene is in an unusual operon, the second example of this type of operon in C. elegans, and encodes the nematode homolog of Extra sex combs, a WD-40 protein in the Polycomb group in Drosophila. mes-2 encodes another Polycomb group protein (see paper by Holdeman, R., Nehrt, S. and Strome, S. (1998). Development 125, 2457–2467). Consistent with the known role of Polycomb group proteins in regulating gene expression, MES-6 is a nuclear protein. It is enriched in the germline of larvae and adults and is present in all nuclei of early embryos. Molecular epistasis results predict that the MES proteins, like Polycomb group proteins in Drosophila, function as a complex to regulate gene expression. Database searches reveal that there are considerably fewer Polycomb group genes in C. elegans than in Drosophila or vertebrates, and our studies suggest that their primary function is in controlling gene expression in the germline and ensuring the survival and proliferation of that tissue.

Development ◽  
1998 ◽  
Vol 125 (13) ◽  
pp. 2457-2467 ◽  
Author(s):  
R. Holdeman ◽  
S. Nehrt ◽  
S. Strome

A unique and essential feature of germ cells is their immortality. In Caenorhabditis elegans, germline immortality requires the maternal contribution from four genes, mes-2, mes-3, mes-4 and mes-6. We report here that mes-2 encodes a protein similar to the Drosophila Polycomb group protein, Enhancer of zeste, and in the accompanying paper that mes-6 encodes another Polycomb group protein. The Polycomb group is responsible for maintaining proper patterns of expression of the homeotic and other genes in Drosophila. It is thought that Polycomb group proteins form heteromeric complexes and control gene expression by altering chromatin conformation of target genes. As predicted from its similarity to a Polycomb group protein, MES-2 localizes to nuclei. MES-2 is found in germline nuclei in larval and adult worms and in all nuclei in early embryos. By the end of embryogenesis, MES-2 is detected primarily in the two primordial germ cells. The correct distribution of MES-2 requires the wild-type functions of mes-3 and mes-6. We hypothesize that mes-2 encodes a maternal regulator of gene expression in the early germline; its function is essential for normal early development and viability of germ cells.


Development ◽  
1998 ◽  
Vol 125 (17) ◽  
pp. 3483-3496 ◽  
Author(s):  
F. Tie ◽  
T. Furuyama ◽  
P.J. Harte

The Polycomb Group gene esc encodes an evolutionarily conserved protein required for transcriptional silencing of the homeotic genes. Unlike other Polycomb Group genes, esc is expressed and apparently required only during early embryogenesis, suggesting it is required for the initial establishment of silencing but not for its subsequent maintenance. We present evidence that the ESC protein interacts directly with E(Z), another Polycomb Group protein required for silencing of the homeotic genes. We show that the most highly conserved region of ESC, containing seven WD motifs that are predicted to fold into a beta-propeller structure, mediate its binding to a conserved N-terminal region of E(Z). Mutations in the WD region that perturb ESC silencing function in vivo also perturb binding to E(Z) in vitro. The entire WD region forms a trypsin-resistant structure, like known beta -propeller domains, and mutations that would affect the predicted ESC beta-propeller perturb its trypsin-resistance, while a putative structure-conserving mutation does not. We show by co-immunoprecipitation that ESC and E(Z) are directly associated in vivo and that they also co-localize at many chromosomal binding sites. Since E(Z) is required for binding of other Polycomb Group proteins to chromosomes, these results suggest that formation of an E(Z):ESC complex at Polycomb Response Elements may be an essential prerequisite for the establishment of silencing.


2013 ◽  
Vol 42 (2) ◽  
pp. 790-803 ◽  
Author(s):  
P. Mathiyalagan ◽  
J. Okabe ◽  
L. Chang ◽  
Y. Su ◽  
X.-J. Du ◽  
...  

Endocrinology ◽  
2012 ◽  
Vol 153 (2) ◽  
pp. 913-924 ◽  
Author(s):  
Yuko Katoh-Fukui ◽  
Kanako Miyabayashi ◽  
Tomoko Komatsu ◽  
Akiko Owaki ◽  
Takashi Baba ◽  
...  

Mice lacking the function of the polycomb group protein CBX2 (chromobox homolog 2; also known as M33) show defects in gonadal, adrenal, and splenic development. In particular, XY knockout (KO) mice develop ovaries but not testes, and the gonads are hypoplastic in both sexes. However, how CBX2 regulates development of these tissues remains largely unknown. In the present study, we used microarray, RT-PCR, and immunohistochemical analyses to show that the expression of Sry, Sox9, Lhx9, Ad4BP/SF-1, Dax-1, Gata4, Arx, and Dmrt1, genes encoding transcription factors essential for gonadal development, is affected in Cbx2 KO gonads. Male-to-female sex reversal in Cbx2 KO mice was rescued by crossing them with transgenic mice displaying forced expression of Sry or Sox9. However, testes remained hypoplastic in these mice, indicating that the size and the sex of the gonad are determined by different sets of genes. Our study implicates Cbx2 in testis differentiation through regulating Sry gene expression.


1998 ◽  
Vol 18 (6) ◽  
pp. 3586-3595 ◽  
Author(s):  
Richard G. A. B. Sewalt ◽  
Johan van der Vlag ◽  
Marco J. Gunster ◽  
Karien M. Hamer ◽  
Jan L. den Blaauwen ◽  
...  

ABSTRACT In Drosophila melanogaster, thePolycomb-group (PcG) andtrithorax-group (trxG) genes have been identified as repressors and activators, respectively, of gene expression. Both groups of genes are required for the stable transmission of gene expression patterns to progeny cells throughout development. Several lines of evidence suggest a functional interaction between the PcG and trxG proteins. For example, genetic evidence indicates that the enhancer of zeste [E(z)] gene can be considered both a PcG and a trxGgene. To better understand the molecular interactions in which the E(z) protein is involved, we performed a two-hybrid screen with Enx1/EZH2, a mammalian homolog of E(z), as the target. We report the identification of the human EED protein, which interacts with Enx1/EZH2. EED is the human homolog ofeed, a murine PcG gene which has extensive homology with the Drosophila PcG gene extra sex combs(esc). Enx1/EZH2 and EED coimmunoprecipitate, indicating that they also interact in vivo. However, Enx1/EZH2 and EED do not coimmunoprecipitate with other human PcG proteins, such as HPC2 and BMI1. Furthermore, unlike HPC2 and BMI1, which colocalize in nuclear domains of U-2 OS osteosarcoma cells, Enx1/EZH2 and EED do not colocalize with HPC2 or BMI1. Our findings indicate that Enx1/EZH2 and EED are members of a class of PcG proteins that is distinct from previously described human PcG proteins.


Development ◽  
1994 ◽  
Vol 120 (9) ◽  
pp. 2629-2636 ◽  
Author(s):  
A. Lonie ◽  
R. D'Andrea ◽  
R. Paro ◽  
R. Saint

The Polycomblike gene of Drosophila melanogaster, a member of the Polycomb Group of genes, is required for the correct spatial expression of the homeotic genes of the Antennapaedia and Bithorax Complexes. Mutations in Polycomb Group genes result in ectopic homeotic gene expression, indicating that Polycomb Group proteins maintain the transcriptional repression of specific homeotic genes in specific tissues during development. We report here the isolation and molecular characterisation of the Polycomblike gene. The Polycomblike transcript encodes an 857 amino acid protein with no significant homology to other proteins. Antibodies raised against the product of this open reading frame were used to show that the Polycomblike protein is found in all nuclei during embryonic development. Antibody staining also revealed that the Polycomblike protein is found on larval salivary gland polytene chromosomes at about 100 specific loci, the same loci to which the Polycomb and polyhomeotic proteins, two other Polycomb Group proteins, are found. These data add further support for a model in which Polycomb Group proteins form multimeric protein complexes at specific chromosomal loci to repress transcription at those loci.


Development ◽  
2001 ◽  
Vol 128 (7) ◽  
pp. 1069-1080 ◽  
Author(s):  
M.A. Jedrusik ◽  
E. Schulze

In remarkable contrast to somatic cells, the germline of the nematode Caenorhabditis elegans efficiently silences transgenic DNA. The molecular mechanisms responsible for this have been shown to implicate chromatin proteins encoded by the mes genes (Kelly, W. G. and Fire, A. (1998) Development 125, 2451–2456), of which two are the C. elegans homologs of Polycomb Group gene transcriptional repressors. We have analyzed the contribution of the histone H1 gene family to this specific aspect of germ cells in C. elegans. We show with isotype-specific double stranded RNA-mediated interference (RNAi) that a single member of this gene family (H1.1) is essential for the repression of a silenced reporter-transgene in the germline of hermaphrodites and males, whereas no change is found in the somatic expression of this reporter. Additionally, RNA-mediated interference with H1.1 gene expression can cause a phenotype with severe affection of germline proliferation and differentiation in the hermaphrodite, and even sterility (5%-11% penetrance). These and further features observed in histone H1.1 RNAi experiments are also characteristic of the mes phenotype (Garvin, C., Holdeman, R. and Strome, S. (1998) Genetics 148, 167–185), which is believed to result from the desilencing of genes required for somatic differentiation in the germline. Our observations therefore support this interpretation of the mes phenotype and they identify a single histone H1 isoform (H1.1) as a new component specifically involved in chromatin silencing in the germline of C. elegans.


Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 2345-2345
Author(s):  
Magda Kucia ◽  
Rui Liu ◽  
Kasia Mierzejewska ◽  
Wan Wu ◽  
Janina Ratajczak ◽  
...  

Abstract Abstract 2345 Recently, we identified a population of very small embryonic-like (VSEL) stem cells (SCs) in adult bone marrow (BM) (Leukemia 2006:20;857). These Oct4+CXCR4+SSEA-1+Sca-1+CD45−Lin− VSELs are capable of differentiation in vitro into cells from all three germ lineages and in in vivo animal models they can be specified into mesenchymal stem cells (MSCs) (Stem Cells Dev 2010:19;1557), cardiomyocytes (Stem Cell 2008:26;1646), and long-term engrafting hematopoietic stem cells (HSCs) (Exp Hematol 2011:39;225). Be employing gene-expression and epigenetic profiling studies we reported that VSELs in BM have germ-line stem cell like epigenetic features including i) open/active chromatin structure in Oct4 promoter, ii) parent-of-origin specific reprogramming of genomic imprinting (Leukemia 2009, 23, 2042–2051), and iii) that they share several markers with epiblast-derived primordial germ cells (PGCs), in particular with migratory PGCs (Leukemia 2010, 24, 1450–1461). However, it was not clear how VSELs maintain pluripotent state. To address this issue we recently employed single cell-based genome-wide gene expression analysis and found that, Oct4+ VSELs i) express a similar, yet nonidentical, transcriptome as embryonic stem-cells (ESCs), ii) up-regulate cell-cycle checkpoint genes, and iii) down-regulate genes involved in protein turnover and mitogenic pathways. Interestingly, our single cell library studies also revelaed that Ezh2, a polycomb group protein, is highly expressed in VSELs. This protein is well known to be involved in maintaining a bivalent domains (BDs) at promoters of important homeodomain-containing developmental transcription factors. Of note a presence of BDs is characteristic for pluripotent stem cells (e.g., ESCs) and as result of Ezh2 overexpression, VSELs, like ESCs, exhibit BDs - bivalently modified nucleosomes (trimethylated H3K27 and H3K4) at promoters of important homeodomain-containing developmental transcription factors (Sox21 Nkx2.2 Dlx1 Zfpm2 Irx2 Lbx1h Hlxb9 Pax5 HoxA3). Of note, spontaneous (as seen during differentiation) or RNA interference-enforced down-regulation of Ezh2 removes BDs what, results in lose of their plurioptentiality and de-repression of several BD-regulated genes that control their tissue commitment. In conclusion, Our results show for first time that in addition to the expression of pluripotency core transcription factor Oct-4, VSELs, like other pluripotent stem-cells, maintain their pluripotent state through an Ezh2-dependent BD-mediated epigenetic mechanism. Based on this our genome-wide gene expression study not only advances our understanding of biological processes that govern VSELs pluripotency, differentiation, and quiescence but will also help to develop better protocols for ex vivo expansion of these promising cells for potential application in regenerative medicine. Disclosures: Ratajczak: Neostem Inc: Consultancy, Research Funding.


eLife ◽  
2014 ◽  
Vol 3 ◽  
Author(s):  
Roberto Bonasio ◽  
Emilio Lecona ◽  
Varun Narendra ◽  
Philipp Voigt ◽  
Fabio Parisi ◽  
...  

Polycomb repressive complex-1 (PRC1) is essential for the epigenetic regulation of gene expression. SCML2 is a mammalian homolog of Drosophila SCM, a Polycomb-group protein that associates with PRC1. In this study, we show that SCML2A, an SCML2 isoform tightly associated to chromatin, contributes to PRC1 localization and also directly enforces repression of certain Polycomb target genes. SCML2A binds to PRC1 via its SPM domain and interacts with ncRNAs through a novel RNA-binding region (RBR). Targeting of SCML2A to chromatin involves the coordinated action of the MBT domains, RNA binding, and interaction with PRC1 through the SPM domain. Deletion of the RBR reduces the occupancy of SCML2A at target genes and overexpression of a mutant SCML2A lacking the RBR causes defects in PRC1 recruitment. These observations point to a role for ncRNAs in regulating SCML2 function and suggest that SCML2 participates in the epigenetic control of transcription directly and in cooperation with PRC1.


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