A subcortical, pigment-containing structure in Xenopus eggs with contractile properties

Merriam, R. W.; Sauterer, Roger; Christensen, Kathy

doi:10.1016/0012-1606(83)90045-3

Cited by 38 publications

(20 citation statements)

References 32 publications

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“…It is established that cytokinesis requires polymerization of actin filaments (F-actin) as well as depolymerization. This requirement for F-actin dynamics is illustrated by the deleterious effects of actin-depolymerizing drugs (Merriam et al, 1983) or inactivation of cofilin, an F-actindepolymerising and -severing factor (Abe et al, 1996). Accordingly, deregulation of signalling pathways that operate on the F-actin polymerization-depolymerization equilibrium eventually affects cytokinesis.…”

Section: Discussionmentioning

confidence: 99%

A functional analysis of MELK in cell division reveals a transition in the mode of cytokinesis during Xenopus development

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Chartrain

Badouel

et al. 2011

Journal of Cell Science

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SummaryMELK is a serine/threonine kinase involved in several cell processes, including the cell cycle, proliferation, apoptosis and mRNA processing. However, its function remains elusive. Here, we explored its role in the Xenopus early embryo and show by knockdown that xMELK (Xenopus MELK) is necessary for completion of cell division. Consistent with a role in cell division, endogenous xMELK accumulates at the equatorial cortex of anaphase blastomeres. Its relocalization is highly dynamic and correlates with a conformational rearrangement in xMELK. Overexpression of xMELK leads to failure of cytokinesis and impairs accumulation at the division furrow of activated RhoA -a pivotal regulator of cytokinesis. Furthermore, endogenous xMELK associates and colocalizes with the cytokinesis organizer anillin. Unexpectedly, our study reveals a transition in the mode of cytokinesis correlated to cell size and that implicates xMELK. Collectively, our findings disclose the importance of xMELK in cytokinesis during early development and show that the mechanism of cytokinesis changes during Xenopus early development.

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Section: Discussionmentioning

confidence: 99%

A functional analysis of MELK in cell division reveals a transition in the mode of cytokinesis during Xenopus development

Page

Chartrain

Badouel

et al. 2011

Journal of Cell Science

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“…All these properties of the ooplasm are also inherent in the cortex as a part of the ooplasm. In amphibians the cortex includes not only the plasma membrane with underlying microfilaments as in the somatic cells, but also part of the ooplasm with cortical and pigment granules, endoplasmic reticulum, and mitochondria (Merriam et al, 1983).…”

Section: Discussionmentioning

confidence: 99%

Contractile proteins and nonerythroid spectrin in oogenesis of Xenopus laevis

Ryabova

Virtanen

Wartiovaara

et al. 1994

Molecular Reproduction Devel

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The distribution of contractile proteins, actin and myosin, and an actin-binding protein, spectrin, was studied in oogenesis of Xenopus laevis. These proteins are present in oocytes already at the previtellogenic stages, which are characterized by their diffuse distribution. The localization of proteins changed with the beginning of vitellogenesis. At all vitellogenic stages, including the fully grown oocyte, animal-vegetal differences were noted in localization of actin and myosin: in the animal hemisphere they appear as fibrillar-like structures, while in the vegetal one they are localized around the yolk platelets. By the end of the oocyte's growth, a cortical gradient appeared: predominant localization of actin and myosin in the cortical area. As the oocyte maturation proceeded, the distribution of actin and myosin again became diffuse and nonuniform, so that a cortical gradient appears. At the beginning of vitellogenesis spectrin is distributed as a network all over the ooplasm, while in the fully grown oocyte it is localized mostly in the subcortical area of the animal hemisphere and, as individual inclusions, in other regions of the oocyte. No spectrin is found by the end of maturation. Actin, myosin, and spectrin are also present in the oocyte's nuclei. Changes in the distribution of contractile proteins and spectrin during oocyte maturation are discussed with respect to the development of cortical contractility, as well as to the changes in spatial distribution of yolk platelets and regional sensitivity of the maturing oocyte to cytochalasin B.

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“…Like other oocytes, XI oocytes are asymmetric cells with a complex internal polarity. On one side, the dark animal pole contains the nucleus, the endoplasmic reticulum (ER) and pigmented granules [1]; on the other side, the germ plasm and a mitochondrial cloud are distributed evenly in the cytoplasm towards the yellow pale vegetal pole [2], [3]. In oocytes, the asymmetry of mRNAs contributes to the maintenance and organization of the cytokeratin network in the vegetal cortex [4], [5].…”

Section: Introductionmentioning

confidence: 99%

The Polarization of the G-Protein Activated Potassium Channel GIRK5 to the Vegetal Pole of Xenopus laevis Oocytes Is Driven by a Di-Leucine Motif

et al. 2013

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The G protein-coupled inwardly-rectifying potassium channels (known as GIRK or Kir3) form functional heterotetramers gated by G-βγ subunits. GIRK channels participate in heart rate modulation and neuronal postsynaptic inhibition in mammals. In Xenopus laevis oocytes, GIRK5 is a functional homomultimer. Previously, we found that phosphorylation of a tyrosine (Y16) at its N-terminus downregulates the surface expression of GIRK5. In this work, we elucidated the subcellular localization and trafficking of GIRK5 in oocytes. Several EGFP-GIRK5 chimeras were produced and an ECFP construct was used to identify the endoplasmic reticulum (ER). Whereas GIRK5-WT was retained in the ER at the animal pole, the phospho-null GIRK5-Y16A was localized to the vegetal pole. Interestingly, a construct with an N-terminal Δ25 deletion produced an even distribution of the channel in the whole oocyte. Through an alanine-scan, we identified an acidic cluster/di-leucine sorting-signal recognition motif between E17 and I22. We quantified the effect of each amino acid residue within this di-leucine motif in determining the distribution of GIRK5 to the animal and vegetal poles. We found that Y16 and I22 contributed to functional expression and were dominant in the polarization of GIRK5. We thus conclude that the N-terminal acidic di-leucine motif of GIRK5 determines its retention and polarized trafficking within Xl oocytes.

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A subcortical, pigment-containing structure in Xenopus eggs with contractile properties

Cited by 38 publications

References 32 publications

A functional analysis of MELK in cell division reveals a transition in the mode of cytokinesis during Xenopus development

A functional analysis of MELK in cell division reveals a transition in the mode of cytokinesis during Xenopus development

Contractile proteins and nonerythroid spectrin in oogenesis of Xenopus laevis

The Polarization of the G-Protein Activated Potassium Channel GIRK5 to the Vegetal Pole of Xenopus laevis Oocytes Is Driven by a Di-Leucine Motif

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