Microtubules Are Required for Completion of Cytokinesis in Sea Urchin Eggs

Larkin, Kay; Danilchik, Michael V.

doi:10.1006/dbio.1999.9395

Cited by 31 publications

(25 citation statements)

References 47 publications

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“…2A). Cells treated with nocodazole (microtubule destabilizing) arrested at M phase and their chromosomes were condensed as reported (Larkin and Danilchik, 1999). In these embryos, Vasa accumulated abnormally in large clumps around the nucleus ( Fig.…”

Section: Vasa Interacts With the Mitotic Apparatus During M-phasementioning

confidence: 68%

The DEAD-box RNA helicase Vasa functions in embryonic mitotic progression in the sea urchin

Yajima

Wessel

2011

Development

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SUMMARYVasa is a broadly conserved ATP-dependent RNA helicase that functions in the germ line of organisms from cnidarians to mammals. Curiously, Vasa is also present in the somatic cells of many animals and functions as a regulator of multipotent cells. Here, we report a mitotic function of Vasa revealed in the sea urchin embryo. We found that Vasa protein is present in all blastomeres of the early embryo and that its abundance oscillates with the cell cycle. Vasa associates with the spindle and the separating sister chromatids at metaphase, and then quickly disappears after telophase. Inhibition of Vasa protein synthesis interferes with proper chromosome segregation, arrests cells at M-phase, and delays overall cell cycle progression. Cdk activity is necessary for the proper localization of Vasa, implying that Vasa is involved in the cyclin-dependent cell cycle network, and Vasa is required for the efficient translation of cyclinB mRNA. Our results suggest an evolutionarily conserved role of Vasa that is independent of its function in germ line determination.

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Section: Vasa Interacts With the Mitotic Apparatus During M-phasementioning

confidence: 68%

The DEAD-box RNA helicase Vasa functions in embryonic mitotic progression in the sea urchin

Yajima

Wessel

2011

Development

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“…Multiple roles have been proposed for microtubules in cleavage plane determination (Rappaport, 1996;Burgess and Chang, 2005), and there is now general agreement that microtubules are required for cleavage plane determination as well as the maintenance of the cleavage furrow and abscission (Wheatley and Wang, 1996;Larkin and Danilchik, 1999). Although the molecular nature of the cleavage stimulus remains unknown, recent studies in sea urchin eggs demonstrated a microtubule-dependent localization of active Rho GTPase at the cleavage plane before furrow initiation (Bement et al, 2005).…”

Section: Global Activation Of Myosin Precedes Cleavage Plane Specificmentioning

confidence: 99%

A Global, Myosin Light Chain Kinase-dependent Increase in Myosin II Contractility Accompanies the Metaphase–Anaphase Transition in Sea Urchin Eggs

Lucero

Stack

Bresnick

et al. 2006

MBoC

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Myosin II is the force-generating motor for cytokinesis, and although it is accepted that myosin contractility is greatest at the cell equator, the temporal and spatial cues that direct equatorial contractility are not known. Dividing sea urchin eggs were placed under compression to study myosin II-based contractile dynamics, and cells manipulated in this manner underwent an abrupt, global increase in cortical contractility concomitant with the metaphase-anaphase transition, followed by a brief relaxation and the onset of furrowing. Prefurrow cortical contractility both preceded and was independent of astral microtubule elongation, suggesting that the initial activation of myosin II preceded cleavage plane specification. The initial rise in contractility required myosin light chain kinase but not Rho-kinase, but both signaling pathways were required for successful cytokinesis. Last, mobilization of intracellular calcium during metaphase induced a contractile response, suggesting that calcium transients may be partially responsible for the timing of this initial contractile event. Together, these findings suggest that myosin II-based contractility is initiated at the metaphaseanaphase transition by Ca 2؉ -dependent myosin light chain kinase (MLCK) activity and is maintained through cytokinesis by both MLCK-and Rho-dependent signaling. Moreover, the signals that initiate myosin II contractility respond to specific cell cycle transitions independently of the microtubule-dependent cleavage stimulus. INTRODUCTIONAt its most fundamental level, cytokinesis in animal cells is brought about by regional differences in cortical contractility that drives partitioning of the cytoplasm into two daughter cells (Wang, 2005). Force generation is accomplished by the transient assembly of a contractile ring, and recent genetic and proteomic approaches have significantly increased our knowledge of ring components and regulatory molecules (Echard et al., 2004;Eggert et al., 2004;Skop et al., 2004). Studies in yeast using green fluorescent protein-tagged ring components have demonstrated that ring components are recruited to the division site in a hierarchical manner that involves the progressive assembly of more complex structures (Lippincott and Li, 1998;Wu et al., 2003;Wu and Pollard, 2005). In contrast, the temporal sequence in which ring components are recruited to the division site in animal cells is not as well resolved; thus, it remains unclear whether the contractile ring assembles in a similar sequential manner. Moreover, it is not known how ring assembly is coordinated in space and time with chromosome segregation. Thus, although great advances have been made in our understanding of the contractile ring itself, fundamental gaps remain in our understanding of the spatiotemporal regulation of cytokinesis.The mechanical nature of cytokinesis was appreciated by early cell biologists (Wilson, 1928;Rappaport, 1996), and for decades investigators have taken advantage of the large size and regular geometry of echinoderm eggs to st...

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“…Microtubule-disrupting experiments indicated that basolateral membrane growth in the cleavage plane requires microtubules (Danilchik et al, 1998;Jesuthasan, 1998). Similarly, Larkin and Danilchik found that furrow microtubules are required in cleaving sea urchin embryos to complete the closure of the cytoplasmic bridge, and proposed that one function of furrow microtubules is to direct vesicles toward a site of fusion at the cytoplasmic bridge to accomplish cell separation (Larkin and Danilchik, 1999). More recently, Skop et al (Skop et al, 2001) and Shuster and Burgess (Shuster and Burgess, 2002) have identified microtubule-dependent membrane-addition events in the final stages of cytokinesis in C. elegans and sea urchin egg cleavage.…”

Section: Introductionmentioning

confidence: 95%

Furrow microtubules and localized exocytosis in cleavingXenopus laevisembryos

Danilchik

Bedrick

Brown

et al. 2003

Journal of Cell Science

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In dividing Xenopus eggs, furrowing is accompanied by expansion of a new domain of plasma membrane in the cleavage plane. The source of the new membrane is known to include a store of oogenetically produced exocytotic vesicles, but the site where their exocytosis occurs has not been described. Previous work revealed a V-shaped array of microtubule bundles at the base of advancing furrows. Cold shock or exposure to nocodazole halted expansion of the new membrane domain, which suggests that these microtubules are involved in the localized exocytosis. In the present report, scanning electron microscopy revealed collections of pits or craters, up to ∼1.5 μm in diameter. These pits are evidently fusion pores at sites of recent exocytosis, clustered in the immediate vicinity of the deepening furrow base and therefore near the furrow microtubules. Confocal microscopy near the furrow base of live embryos labeled with the membrane dye FM1-43 captured time-lapse sequences of individual exocytotic events in which irregular patches of ∼20 μm2 of unlabeled membrane abruptly displaced pre-existing FM1-43-labeled surface. In some cases, stable fusion pores, approximately 2 μm in diameter, were seen at the surface for up to several minutes before suddenly delivering patches of unlabeled membrane. To test whether the presence of furrow microtubule bundles near the surface plays a role in directing or concentrating this localized exocytosis, membrane expansion was examined in embryos exposed to D2O to induce formation of microtubule monasters randomly under the surface. D2O treatment resulted in a rapid, uniform expansion of the egg surface via random, ectopic exocytosis of vesicles. This D2O-induced membrane expansion was completely blocked with nocodazole, indicating that the ectopic exocytosis was microtubule-dependent. Results indicate that exocytotic vesicles are present throughout the egg subcortex, and that the presence of microtubules near the surface is sufficient to mobilize them for exocytosis at the end of the cell cycle.

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Microtubules Are Required for Completion of Cytokinesis in Sea Urchin Eggs

Cited by 31 publications

References 47 publications

The DEAD-box RNA helicase Vasa functions in embryonic mitotic progression in the sea urchin

The DEAD-box RNA helicase Vasa functions in embryonic mitotic progression in the sea urchin

A Global, Myosin Light Chain Kinase-dependent Increase in Myosin II Contractility Accompanies the Metaphase–Anaphase Transition in Sea Urchin Eggs

Furrow microtubules and localized exocytosis in cleavingXenopus laevisembryos

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