Generation of asymmetry and segregation of germ-line granules in early C. elegans embryos

Strome, Susan; Wood, William B.

doi:10.1016/0092-8674(83)90203-9

Cited by 522 publications

(358 citation statements)

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“…We examined this response in C. elegans, by using nocodazole to destabilize microtubules in two-cell stage embryos (see Materials and Methods). In earlier studies, nocodazole was shown to largely, although not entirely, deplete spindle microtubules in dividing one-cell stage C. elegans embryos, without arresting mitosis (Strome and Wood, 1983;Hyman and White, 1987). Exposing onecell embryos to nocodazole produced variable effects (our unpublished data), possibly due to variability in the postfertilization age of one-cell embryos dissected from adults when exposed to this chemical.…”

Section: A Functional Spindle Checkpoint In the Early C Elegans Embryomentioning

confidence: 99%

“…Application of nocodazole at this time prevented the reformation of astral microtubules during the second cell division. Although in earlier studies the eggshell was cracked to introduce nocodazole into the early embryo (Strome and Wood, 1983), we have found that nocodazole can effectively penetrate the early embryo eggshell without cracking, as determined by mispositioned mitotic spindles and the partial depletion of microtubules of one-and two-cell embryos (Kurz et al, 2002). Slides were overlaid with a 22 ϫ 22-mm glass coverslip and sealed with melted petroleum jelly.…”

Section: Nocodazole Treatmentmentioning

confidence: 99%

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A Spindle Checkpoint Functions during Mitosis in the EarlyCaenorhabditis elegansEmbryo

Encalada

Willis

Lyczak

et al. 2005

MBoC

118

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During mitosis, chromosome segregation is regulated by a spindle checkpoint mechanism. This checkpoint delays anaphase until all kinetochores are captured by microtubules from both spindle poles, chromosomes congress to the metaphase plate, and the tension between kinetochores and their attached microtubules is properly sensed. Although the spindle checkpoint can be activated in many different cell types, the role of this regulatory mechanism in rapidly dividing embryonic animal cells has remained controversial. Here, using time-lapse imaging of live embryonic cells, we show that chemical or mutational disruption of the mitotic spindle in early Caenorhabditis elegans embryos delays progression through mitosis. By reducing the function of conserved checkpoint genes in mutant embryos with defective mitotic spindles, we show that these delays require the spindle checkpoint. In the absence of a functional checkpoint, more severe defects in chromosome segregation are observed in mutants with abnormal mitotic spindles. We also show that the conserved kinesin CeMCAK, the CENP-F-related proteins HCP-1 and HCP-2, and the core kinetochore protein CeCENP-C all are required for this checkpoint. Our analysis indicates that spindle checkpoint mechanisms are functional in the rapidly dividing cells of an early animal embryo and that this checkpoint can prevent chromosome segregation defects during mitosis. INTRODUCTIONDuring mitosis, some microtubules emanating from bipolar microtubule organizing centers grow toward chromosomes and attach to specialized chromosomal regions called kinetochores (Skibbens and Hieter, 1998;Cleveland et al., 2003). Once captured, sister chromatids are segregated, one to each of two daughter cells. Eukaryotic cells have evolved a mechanism called the spindle checkpoint, to monitor chromosomal segregation and increase the fidelity of mitosis (reviewed in Gardner and Burke, 2000;McIntosh et al., 2002). Until spindle microtubules from both poles capture and align all sister chromatid pairs at a metaphase plate, the spindle checkpoint produces a delay in the onset of anaphase. If this delay is bypassed by reducing checkpoint function, anaphase starts prematurely, and daughter cells may receive unequal complements of chromosomes. Such genomic instability can result in lethality and in tumorigenesis (Hartwell and Kastan, 1994;Basu et al., 1999).Originally identified and characterized in Saccharomyces cerevisiae, seven spindle assembly checkpoint genes (MAD1, MAD2, MAD3, BUB1, BUB2, BUB3, and MPS1) are known to function at kinetochores to inhibit anaphase onset, or to mediate mitotic exit in the presence of spindle abnormalities (Hoyt et al., 1991;Li and Murray, 1991). Mutations in these genes reduce or eliminate the cell cycle delays that normally occur after treatment with microtubule depolymerizing drugs (Wang and Burke, 1995;Pangilinan and Spencer, 1996). Bub1 and Bub3 form a protein kinase complex that, in concert with Mps1, functions at kinetochores upstream of Mad1 and Mad2 (Roberts et al., 1994;H...

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Section: A Functional Spindle Checkpoint In the Early C Elegans Embryomentioning

confidence: 99%

Section: Nocodazole Treatmentmentioning

confidence: 99%

A Spindle Checkpoint Functions during Mitosis in the EarlyCaenorhabditis elegansEmbryo

Encalada

Willis

Lyczak

et al. 2005

MBoC

118

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“…For antibody staining, worms were permeabilized by using the freeze-crack method, fixed for 10 min in methanol and 10 min in acetone, and stained as described (38). Antibody dilutions were 1:30,000 rabbit anti-PGL-1 (26), 1:500 guinea pig anti-HTP-3 (39), 1:50,000 rat anti-PGL-3 (40), 1:200 rabbit anti-CEH-18 (41), and 1:500 Alexa Fluor secondary antibodies (Life Technologies).…”

Section: Methodsmentioning

confidence: 99%

Reevaluation of whether a soma–to–germ-line transformation extends lifespan in Caenorhabditis elegans

Knutson

Rechtsteiner

Strome

2016

Proc. Natl. Acad. Sci. U.S.A.

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The germ lineage is considered to be immortal. In the quest to extend lifespan, a possible strategy is to drive germ-line traits in somatic cells, to try to confer some of the germ lineage's immortality on the somatic body. Notably, a study in Caenorhabditis elegans suggested that expression of germ-line genes in the somatic cells of long-lived daf-2 mutants confers some of daf-2's long lifespan. Specifically, mRNAs encoding components of C. elegans germ granules (P granules) were up-regulated in daf-2 mutant worms, and knockdown of individual P-granule and other germ-line genes in daf-2 young adults modestly reduced their lifespan. We investigated the contribution of a germ-line program to daf-2's long lifespan and also tested whether other mutants known to express germ-line genes in their somatic cells are long-lived. Our key findings are as follows. (i) We could not detect P-granule proteins in the somatic cells of daf-2 mutants by immunostaining or by expression of a P-granule transgene. (ii) Whole-genome transcript profiling of animals lacking a germ line revealed that germ-line transcripts are not up-regulated in the soma of daf-2 worms compared with the soma of control worms. (iii) Simultaneous removal of multiple P-granule proteins or the entire germ-line program from daf-2 worms did not reduce their lifespan. (iv) Several mutants that robustly express a broad spectrum of germ-line genes in their somatic cells are not long-lived. Together, our findings argue against the hypothesis that acquisition of a germ-cell program in somatic cells increases lifespan and contributes to daf-2's long lifespan.germ line | aging | C. elegans | daf-2 | P granules G erm and soma are the two most fundamentally different cell types found in multicellular organisms (1). Germ cells are totipotent and constitute the only immortal lineage, capable of generating entire new organisms generation after generation, whereas somatic cells differentiate into specialized cell types and are mortal, senescing and dying each generation. Maintaining the proper identity of these cell types is essential for propagation of species, and molecular barriers at both the transcriptional and translational levels have evolved to ensure the germ-soma distinction (1). Removal of these barriers in germ cells can lead to both expression of somatic factors and sterility (2-4), whereas removal of these barriers in somatic cells is associated with reentry into the cell cycle and cancer (5, 6). Despite these barriers, it is unknown whether some cell types can tolerate partial fate switching and perhaps adopt traits of other cell types to benefit the organism.An attractive possibility is that acquisition of a germ-cell program by the somatic body can capture some of the immortality of the germ lineage and extend lifespan (7,8). Indeed, a study in Caenorhabditis elegans supports that possibility (9). In C. elegans, inhibition of the insulin-like signaling pathway by a mutation in daf-2 doubles lifespan through activation of the FOXO transcription factor DAF-16...

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“…Centrosome centration depends mostly on the microtubule cytoskeleton. 4,8 Because the centration depends on filamentous microtubules, the candidate mechanisms can be roughly divided into anticipated number of anchors to contact a single microtubule is proportional to the surface area covered by the microtubule, the force on a single microtubule should be roughly proportional to the squared length of the microtubule (L 2 ). 25 The assumption that the pulling force generator is limited in number is based on an experimental estimation.…”

mentioning

confidence: 99%

A novel mechanism of microtubule length-dependent force to pull centrosomes toward the cell center

Kimura

2011

BioArchitecture

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t he centrosome is a major microtubule-organizing center in animal cells, and its intracellular positioning is critical for defining intracellular architecture. the centrosome positions itself at the cell center. centrosome centration depends on the microtubule cytoskeleton. to accomplish robust centration regardless of the cell size or cell shape, it has been assumed that the force mediated by the microtubules depends on microtubule length. however, a concrete mechanism to generate forces to pull the centrosome in a microtubule lengthdependent manner has been elusive. recently, we successfully demonstrated that centrosome-directed movement of intracellular organelles along microtubules drives centrosome centration in the Caenorhabditis elegans early embryo. based on this observation, we proposed the centrosome-organelle mutual pulling model in which the reaction forces of organelle transport generated along microtubules act as a driving force that pulls the centrosomes toward the cell center. this is the first experiment-based model that accounts for the microtubule length-dependent pulling force generated in the cytoplasm contributing to centrosome centration. intriguingly, this model is consistent with a recent estimation that the pulling force is proportional to the cubic length of microtubules. The Emergence of Order in Cell ArchitectureThe cell can be compared to a city. A population of macromolecules lives their lives inside the cell, and they utilize the a novel mechanism of microtubule length-dependent force to pull centrosomes toward the cell center

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Generation of asymmetry and segregation of germ-line granules in early C. elegans embryos

Cited by 522 publications

References 25 publications

A Spindle Checkpoint Functions during Mitosis in the EarlyCaenorhabditis elegansEmbryo

A Spindle Checkpoint Functions during Mitosis in the EarlyCaenorhabditis elegansEmbryo

Reevaluation of whether a soma–to–germ-line transformation extends lifespan in Caenorhabditis elegans

A novel mechanism of microtubule length-dependent force to pull centrosomes toward the cell center

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