Cortical anchorages and cell type segregations of maternal postplasmic/PEM RNAs in ascidians

Paix, Alexandre; Yamada, Lixy; Dru, Philippe; Lecordier, Helene; Prulière, Gérard; Chênevert, Janet; Satoh, Nori; Sardet, Christian

doi:10.1016/j.ydbio.2009.09.001

Cited by 33 publications

(42 citation statements)

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“…S3A,B in the supplementary material), indicating that, like its mRNA, it was maternally supplied. However, contrary to the accumulation of pem-1 mRNA in the cortex of unfertilized eggs and one-cell stage embryos (Paix et al, 2009;Prodon et al, 2005;Prodon et al, 2006), the Ci-Pem-1 protein was distributed in the cytoplasm with the enrichment to the vegetal pole (see Fig. S3B-D in the supplementary material).…”

Section: Ci-pem-1 Is Highly Concentrated In the Nuclei Of Germline Blmentioning

confidence: 89%

“…2AЉ-EЉ, arrowhead). Although the Ci-pem-1 RNA is inherited only by the B8.11 cells upon the division of the B7.6 cell in the 110-cell-stage embryo (Paix et al, 2009;Shirae-Kurabayashi et al, 2006), the CiPem-1 protein was distributed into both the B8.11 and B8.12 daughter cells (data not shown). Subsequently, Ci-Pem-1 signals in the B8.12 PGCs dropped during the neural-plate stage, and became undetectable by the tailbud stage (see Fig.…”

Section: Ci-pem-1 Is Highly Concentrated In the Nuclei Of Germline Blmentioning

confidence: 95%

“…Although the CAB remnants and associated postplasmic/PEM RNAs are specifically partitioned into the B8.11 cells, a group of the postplasmic/PEM RNAs, including CiVH, are diffused from the postplasm during the B7.6 cell division and segregated into the B8.12 cells (Paix et al, 2009;Shirae-Kurabayashi et al, 2006;Yamada, 2006). As only the progeny of the B8.12 cells migrates into the gonad after metamorphosis, the B8.12 cells are regarded as PGCs in ascidians (Shirae-Kurabayashi et al, 2006), indicating that the postplasmcontaining blastomeres at the posterior pole of ascidian embryos (hereinafter 'the germline blastomeres') retain the potential to develop into germ cells.…”

Section: Introductionmentioning

confidence: 99%

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Ci-Pem-1 localizes to the nucleus and represses somatic gene transcription in the germline of Ciona intestinalis embryos

Shirae-Kurabayashi¹,

Matsuda²,

Nakamura³

2011

Development

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In many animal embryos, germ-cell formation depends on maternal factors located in the germ plasm. To ensure the development of germ cells, germline progenitors must be prevented from differentiating inappropriately into somatic cells. A common mechanism for this appears to be the active repression of somatic gene transcription. Species-specific germ-plasm components, such as Pgc in Drosophila and PIE-1 in C. elegans, establish germline transcriptional quiescence by inhibiting general transcriptional machineries. In the ascidian Ciona intestinalis, although transcriptional repression in the germline has been proposed, the factors and mechanisms involved have been unknown. We found that the protein products of Ci-pem-1 RNA, which is an ascidian-specific component of the postplasm (the germ plasm equivalent in ascidians), localized to the nucleus of germline blastomeres, as well as to the postplasm. Morpholino oligonucleotide-mediated Ci-pem-1 knockdown resulted in the ectopic expression of several somatic genes that are usually silent in the germline. In the Ci-pem-1 knockdown embryos, the expression of both β-catenin- and GATAa-dependent genes was derepressed in the germline blastomeres, suggesting that Ci-Pem-1 broadly represses germline mRNA transcription. Immunoprecipitation assays showed that Ci-Pem-1 could interact with two C. intestinalis homologs of Groucho, which is a general co-repressor of mRNA transcription. These results suggest that Ci-pem-1 is the C. intestinalis version of a germ-plasm RNA whose protein product represses the transcription of somatic genes during specification of the germ-cell fate, and that this repression may be operated through interactions between Ci-Pem-1 and Groucho co-repressors.

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Section: Ci-pem-1 Is Highly Concentrated In the Nuclei Of Germline Blmentioning

confidence: 89%

Section: Ci-pem-1 Is Highly Concentrated In the Nuclei Of Germline Blmentioning

confidence: 95%

Section: Introductionmentioning

confidence: 99%

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Ci-Pem-1 localizes to the nucleus and represses somatic gene transcription in the germline of Ciona intestinalis embryos

Shirae-Kurabayashi¹,

Matsuda²,

Nakamura³

2011

Development

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“…It is a large (~15 m) cortical structure that is present during all phases of the cell cycle and accumulates polarity complex proteins PAR3, PAR6 and aPKC (Patalano et al, 2006), as well as approximately 40 postplasmic/PEM RNAs (Prodon et al, 2007;Paix et al, 2009). The nucleus and associated centrosomes migrate towards the CAB during interphase (Hibino et al, 1998;Patalano et al, 2006).…”

Section: Discussionmentioning

confidence: 99%

“…Here a macroscopic structure visible by light microscopy, termed the centrosome-attracting body (CAB), is required for each of these unequal cleavages, generating two small posterior cells that give rise to the germ lineage (Nishikata et al, 1999). About 40 maternal postplasmic/PEM RNAs accumulate in the CAB, including at least two determinants, Macho1 and Pem1 (Yamada, 2006;Prodon et al, 2007;Paix et al, 2009), as well as the germcell marker Vasa (Fujimura and Takamura, 2000;Paix et al, 2009). The CAB also accumulates a submembranous layer of cortical polarity proteins PAR3, PAR6 and aPKC (Patalano et al, 2006), which are known to be involved in spindle orientation in C. elegans one-cell embryos, Drosophila neuroblasts and mammalian epithelial cells (for a review, see Siller and Doe, 2009).…”

Section: Introductionmentioning

confidence: 99%

Dual mechanism controls asymmetric spindle position in ascidian germ cell precursors

et al. 2010

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SUMMARYMitotic spindle orientation with respect to cortical polarity cues generates molecularly distinct daughter cells during asymmetric cell division (ACD). However, during ACD it remains unknown how the orientation of the mitotic spindle is regulated by cortical polarity cues until furrowing begins. In ascidians, the cortical centrosome-attracting body (CAB) generates three successive unequal cleavages and the asymmetric segregation of 40 localized postplasmic/PEM RNAs in germ cell precursors from the 8-64 cell stage. By combining fast 4D confocal fluorescence imaging with gene-silencing and classical blastomere isolation experiments, we show that spindle repositioning mechanisms are active from prometaphase until anaphase, when furrowing is initiated in B5.2 cells. We show that the vegetal-most spindle pole/centrosome is attracted towards the CAB during prometaphase, causing the spindle to position asymmetrically near the cortex. Next, during anaphase, the opposite spindle pole/centrosome is attracted towards the border with neighbouring B5.1 blastomeres, causing the spindle to rotate (10°/minute) and migrate (3 m/minute). Dynamic 4D fluorescence imaging of filamentous actin and plasma membrane shows that precise orientation of the cleavage furrow is determined by this second phase of rotational spindle displacement. Furthermore, in pairs of isolated B5.2 blastomeres, the second phase of rotational spindle displacement was lost. Finally, knockdown of PEM1, a protein localized in the CAB and required for unequal cleavage in B5.2 cells, completely randomizes spindle orientation. Together these data show that two separate mechanisms active during mitosis are responsible for spindle positioning, leading to precise orientation of the cleavage furrow during ACD in the cells that give rise to the germ lineage in ascidians.

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Intracellular RNA Localization and Localized Translation

Besse

2013

Encyclopedia of Molecular Cell Biology and Molecular Medicine

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Cortical anchorages and cell type segregations of maternal postplasmic/PEM RNAs in ascidians

Cited by 33 publications

References 50 publications

Ci-Pem-1 localizes to the nucleus and represses somatic gene transcription in the germline of Ciona intestinalis embryos

Ci-Pem-1 localizes to the nucleus and represses somatic gene transcription in the germline of Ciona intestinalis embryos

Dual mechanism controls asymmetric spindle position in ascidian germ cell precursors

Intracellular RNA Localization and Localized Translation

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