scholarly journals Kinesin-1 mediates translocation of the meiotic spindle to the oocyte cortex through KCA-1, a novel cargo adapter

2005 ◽  
Vol 169 (3) ◽  
pp. 447-457 ◽  
Author(s):  
Hsin-ya Yang ◽  
Paul E. Mains ◽  
Francis J. McNally
Keyword(s):  
Meiotic Spindle ◽  
Cell Cortex ◽  
Anaphase Promoting Complex ◽  
Wild Type ◽  
Kinesin Light Chain ◽  
Polar Bodies ◽  
Meiotic Spindles ◽  
Redundant Mechanism ◽  
Meiosis I ◽  
Egg Cortex

In animals, female meiotic spindles are attached to the egg cortex in a perpendicular orientation at anaphase to allow the selective disposal of three haploid chromosome sets into polar bodies. We have identified a complex of interacting Caenorhabditis elegans proteins that are involved in the earliest step in asymmetric positioning of anastral meiotic spindles, translocation to the cortex. This complex is composed of the kinesin-1 heavy chain orthologue, UNC-116, the kinesin light chain orthologues, KLC-1 and -2, and a novel cargo adaptor, KCA-1. Depletion of any of these subunits by RNA interference resulted in meiosis I metaphase spindles that remained stationary at a position several micrometers from the cell cortex during the time when wild-type spindles translocated to the cortex. After this prolonged stationary period, unc-116(RNAi) spindles moved to the cortex through a partially redundant mechanism that is dependent on the anaphase-promoting complex. This study thus reveals two sequential mechanisms for translocating anastral spindles to the oocyte cortex.

scholarly journals Localization of the mei-1 gene product of Caenorhaditis elegans, a meiotic-specific spindle component.

1994 ◽  
Vol 126 (1) ◽  
pp. 199-209 ◽  
Author(s):  
S Clark-Maguire ◽  
P E Mains
Keyword(s):  
Regulatory Network ◽  
Meiotic Spindle ◽  
Loss Of Function ◽  
Wild Type ◽  
Female Meiosis ◽  
Gain Of Function ◽  
Spindle Poles ◽  
Meiotic Spindles ◽  
Female Germline ◽  
Meiosis I

Genetic evidence suggests that the product of the mei-1 gene of Caenorhabditis elegans is specifically required for meiosis in the female germline. Loss-of-function mei-1 mutations block meiotic spindle formation while a gain-of-function allele instead results in spindle defects during the early mitotic cleavages. In this report, we use immunocytochemistry to examine the localization of the mei-1 product in wild-type and mutant embryos. During metaphase of meiosis I in wild-type embryos, mei-1 protein was found throughout the spindle but was more concentrated toward the poles. At telophase I, mei-1 product colocalized with the chromatin at the spindle poles. The pattern was repeated during meiosis II but no mei-1 product was visible during the subsequent mitotic cleavages. The mei-1 gain-of-function allele resulted in ectopic mei-1 staining in the centers of the microtubule-organizing centers during interphase and in the spindles during the early cleavages. This aberrant localization is probably responsible for the poorly formed and misoriented cleavage spindles characteristic of the mutation. We also examined the localization of mei-1(+) product in the presence of mutations of genes that genetically interact with mei-1 alleles. mei-2 is apparently required to localize mei-1 product to the spindle during meiosis while mel-26 acts as a postmeiotic inhibitor. We conclude that mei-1 encodes a novel spindle component, one that is specialized for the acentriolar meiotic spindles unique to female meiosis. The genes mei-2 and mel-26 are part of a regulatory network that confines mei-1 activity to meiosis.

Maize meiotic spindles assemble around chromatin and do not require paired chromosomes

1998 ◽  
Vol 111 (23) ◽  
pp. 3507-3515 ◽  
Author(s):  
A. Chan ◽  
W.Z. Cande
Keyword(s):  
Nuclear Envelope ◽  
Higher Plants ◽  
Metaphase Plate ◽  
Meiotic Spindle ◽  
Wild Type ◽  
Homologous Chromosomes ◽  
Nuclear Envelope Breakdown ◽  
Meiotic Spindles ◽  
Meiotic Mutations ◽  
Bipolar Spindles

To understand how the meiotic spindle is formed and maintained in higher plants, we studied the organization of microtubule arrays in wild-type maize meiocytes and three maize meiotic mutants, desynaptic1 (dsy1), desynaptic2 (dsy2), and absence of first division (afd). All three meiotic mutations have abnormal chromosome pairing and produce univalents by diakinesis. Using these three mutants, we investigated how the absence of paired homologous chromosomes affects the assembly and maintenance of the meiotic spindle. Before nuclear envelope breakdown, in wild-type meiocytes, there were no bipolar microtubule arrays. Instead, these structures formed after nuclear envelope breakdown and were associated with the chromosomes. The presence of univalent chromosomes in dsy1, dsy2, and afd meiocytes and of unpaired sister chromatids in the afd meiocytes did not affect the formation of bipolar spindles. However, alignment of chromosomes on the metaphase plate and subsequent anaphase chromosome segregation were perturbed. We propose a model for spindle formation in maize meiocytes in which microtubules initially appear around the chromosomes during prometaphase and then the microtubules self-organize. However, this process does not require paired kinetochores to establish spindle bipolarity.

Role of microtubules and microtubule organizing centers on meiotic chromosome elimination in Sciara ocellaris

1997 ◽  
Vol 110 (6) ◽  
pp. 721-730 ◽  
Author(s):  
M.R. Esteban ◽  
M.C. Campos ◽  
A.L. Perondini ◽  
C. Goday
Keyword(s):  
Meiotic Chromosome ◽  
Chromosome Elimination ◽  
Male Meiosis ◽  
Meiotic Spindle ◽  
Monopolar Spindle ◽  
Meiotic Spindles ◽  
Cytoplasmic Microtubules ◽  
Spindle Microtubules ◽  
Meiosis I

Spindle formation and chromosome elimination during male meiosis in Sciara ocellaris (Diptera, Sciaridae) has been studied by immunofluorescence techniques. During meiosis I a monopolar spindle is formed from a single polar complex (centrosome-like structure). This single centrosomal structure persists during meiosis II and is responsible for the non-disjunction of the maternal X chromatids. During meiosis I and II non-spindle microtubules are assembled in the cytoplasmic bud regions of the spermatocytes. The chromosomes undergoing elimination during both meiotic divisions are segregated to the bud region where they associate with bundles of microtubules. The presence and distribution of centrosomal antigens in S. ocellaris meiotic spindles and bud regions has been investigated using different antibodies. gamma-Tubulin and centrin are present in the bud as well as in the single polar complex of first meiotic spindle. The results suggest that spermatocyte bud regions contain microtubule-organizing centres (MTOCs) that nucleate cytoplasmic microtubules that are involved in capturing chromosomes in the bud regions. The distribution of actin and myosin in the spermatocytes during meiosis is also reported.

scholarly journals Dynactin-dependent cortical dynein and spherical spindle shape correlate temporally with meiotic spindle rotation in Caenorhabditis elegans

2015 ◽  
Vol 26 (17) ◽  
pp. 3030-3046 ◽  
Author(s):  
Marina E. Crowder ◽  
Jonathan R. Flynn ◽  
Karen P. McNally ◽  
Daniel B. Cortes ◽  
Kari L. Price ◽  
...  
Keyword(s):  
Caenorhabditis Elegans ◽  
Spherical Shape ◽  
Nematode Species ◽  
Meiotic Spindle ◽  
Present Evidence ◽  
Basic Domain ◽  
C Elegans ◽  
Polar Bodies ◽  
Spindle Rotation ◽  
Meiotic Spindles

Oocyte meiotic spindles orient with one pole juxtaposed to the cortex to facilitate extrusion of chromosomes into polar bodies. In Caenorhabditis elegans, these acentriolar spindles initially orient parallel to the cortex and then rotate to the perpendicular orientation. To understand the mechanism of spindle rotation, we characterized events that correlated temporally with rotation, including shortening of the spindle in the pole-to pole axis, which resulted in a nearly spherical spindle at rotation. By analyzing large spindles of polyploid C. elegans and a related nematode species, we found that spindle rotation initiated at a defined spherical shape rather than at a defined spindle length. In addition, dynein accumulated on the cortex just before rotation, and microtubules grew from the spindle with plus ends outward during rotation. Dynactin depletion prevented accumulation of dynein on the cortex and prevented spindle rotation independently of effects on spindle shape. These results support a cortical pulling model in which spindle shape might facilitate rotation because a sphere can rotate without deforming the adjacent elastic cytoplasm. We also present evidence that activation of spindle rotation is promoted by dephosphorylation of the basic domain of p150 dynactin.

scholarly journals EMB-30: An APC4 Homologue Required for Metaphase-to-Anaphase Transitions during Meiosis and Mitosis in Caenorhabditis elegans

2000 ◽  
Vol 11 (4) ◽  
pp. 1401-1419 ◽  
Author(s):  
Tokiko Furuta ◽  
Simon Tuck ◽  
Jay Kirchner ◽  
Bryan Koch ◽  
Roy Auty ◽  
...  
Keyword(s):  
Positional Cloning ◽  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Class I ◽  
Meiotic Spindle ◽  
Anaphase Promoting Complex ◽  
Anaphase Onset ◽  
Polar Bodies ◽  
M Phase ◽  
Set Up

Here we show that emb-30 is required for metaphase-to-anaphase transitions during meiosis and mitosis inCaenorhabditis elegans. Germline-specificemb-30 mutant alleles block the meiotic divisions. Mutant oocytes, fertilized by wild-type sperm, set up a meiotic spindle but do not progress to anaphase I. As a result, polar bodies are not produced, pronuclei fail to form, and cytokinesis does not occur. Severe-reduction-of-function emb-30 alleles (class I alleles) result in zygotic sterility and lead to germline and somatic defects that are consistent with an essential role in promoting the metaphase-to-anaphase transition during mitosis. Analysis of the vulval cell lineages in these emb-30(class I) mutant animals suggests that mitosis is lengthened and eventually arrested when maternally contributed emb-30 becomes limiting. By further reducing maternal emb-30 function contributed to class I mutant animals, we show that emb-30 is required for the metaphase-to-anaphase transition in many, if not all, cells. Metaphase arrest in emb-30 mutants is not due to activation of the spindle assembly checkpoint but rather reflects an essential emb-30 requirement for M-phase progression. A reduction in emb-30 activity can suppress the lethality and sterility caused by a null mutation in mdf-1, a component of the spindle assembly checkpoint machinery. This result suggests that delaying anaphase onset can bypass the spindle checkpoint requirement for normal development. Positional cloning established thatemb-30 encodes the likely C. elegansorthologue of APC4/Lid1, a component of the anaphase-promoting complex/cyclosome, required for the metaphase-to-anaphase transition. Thus, the anaphase-promoting complex/cyclosome is likely to be required for all metaphase-to-anaphase transitions in a multicellular organism.

scholarly journals Failure of pronuclear migration and repeated divisions of polar body nuclei associated with MTOC defects in polo eggs of Drosophila

2000 ◽  
Vol 113 (18) ◽  
pp. 3341-3350 ◽  
Author(s):  
M.G. Riparbelli ◽  
G. Callaini ◽  
D.M. Glover
Keyword(s):  
Polar Body ◽  
Motor Protein ◽  
Meiotic Spindle ◽  
Wild Type ◽  
Female Meiosis ◽  
Male Pronucleus ◽  
Female Pronucleus ◽  
Sperm Aster ◽  
Meiosis I

The meiotic spindle of Drosophila oocytes is acentriolar but develops an unusual central microtubule organising centre (MTOC) at the end of meiosis I. In polo oocytes, this common central pole for the two tandem spindles of meiosis II was poorly organised and in contrast to wild-type failed to maintain its associated Pav-KLP motor protein. Furthermore, the polar body nuclei failed to arrest at metaphase, and the four products of female meiosis all underwent repeated haploid division cycles on anastral spindles. This was linked to a failure to form the astral array of microtubules with which the polar body chromosomes are normally associated. The MTOC associated with the male pronucleus was also defective in polo eggs, and the sperm aster did not grow. Migration of the female pronucleus did not take place and so a gonomeric spindle could not form. We discuss these findings in relation to the known roles of polo like kinases in regulating the behaviour of MTOCs.

scholarly journals Spindle Dynamics during Meiosis in Drosophila Oocytes

1997 ◽  
Vol 137 (6) ◽  
pp. 1321-1336 ◽  
Author(s):  
Sharyn A. Endow ◽  
Donald J. Komma
Keyword(s):  
Fluorescent Protein ◽  
Meiotic Spindle ◽  
Oocyte Activation ◽  
New Information ◽  
Microtubule Motor ◽  
Meiotic Spindles ◽  
Green Fluorescent ◽  
Microtubule Motor Protein ◽  
Meiosis I

Mature oocytes of Drosophila are arrested in metaphase of meiosis I. Upon activation by ovulation or fertilization, oocytes undergo a series of rapid changes that have not been directly visualized previously. We report here the use of the Nonclaret disjunctional (Ncd) microtubule motor protein fused to the green fluorescent protein (GFP) to monitor changes in the meiotic spindle of live oocytes after activation in vitro. Meiotic spindles of metaphase-arrested oocytes are relatively stable, however, meiotic spindles of in vitro–activated oocytes are highly dynamic: the spindles elongate, rotate around their long axis, and undergo an acute pivoting movement to reorient perpendicular to the oocyte surface. Many oocytes spontaneously complete the meiotic divisions, permitting visualization of progression from meiosis I to II. The movements of the spindle after oocyte activation provide new information about the dynamic changes in the spindle that occur upon re-entry into meiosis and completion of the meiotic divisions. Spindles in live oocytes mutant for a lossof-function ncd allele fused to gfp were also imaged. The genesis of spindle defects in the live mutant oocytes provides new insights into the mechanism of Ncd function in the spindle during the meiotic divisions.

scholarly journals The spindle assembly checkpoint is not essential for CSF arrest of mouse oocytes

2004 ◽  
Vol 167 (6) ◽  
pp. 1037-1050 ◽  
Author(s):  
Chizuko Tsurumi ◽  
Steffen Hoffmann ◽  
Stephan Geley ◽  
Ralph Graeser ◽  
Zbigniew Polanski
Keyword(s):  
Spindle Assembly Checkpoint ◽  
Spindle Assembly ◽  
Dominant Negative ◽  
Meiotic Spindle ◽  
Anaphase Promoting Complex ◽  
Mouse Oocytes ◽  
Cytostatic Factor ◽  
C Complex ◽  
Meiosis I

In Xenopus oocytes, the spindle assembly checkpoint (SAC) kinase Bub1 is required for cytostatic factor (CSF)-induced metaphase arrest in meiosis II. To investigate whether matured mouse oocytes are kept in metaphase by a SAC-mediated inhibition of the anaphase-promoting complex/cyclosome (APC/C) complex, we injected a dominant-negative Bub1 mutant (Bub1dn) into mouse oocytes undergoing meiosis in vitro. Passage through meiosis I was accelerated, but even though the SAC was disrupted, injected oocytes still arrested at metaphase II. Bub1dn-injected oocytes released from CSF and treated with nocodazole to disrupt the second meiotic spindle proceeded into interphase, whereas noninjected control oocytes remained arrested at metaphase. Similar results were obtained using dominant-negative forms of Mad2 and BubR1, as well as checkpoint resistant dominant APC/C activating forms of Cdc20. Thus, SAC proteins are required for checkpoint functions in meiosis I and II, but, in contrast to frog eggs, the SAC is not required for establishing or maintaining the CSF arrest in mouse oocytes.

scholarly journals Metaphase to Anaphase (mat) Transition–Defective Mutants inCaenorhabditis elegans

2000 ◽  
Vol 151 (7) ◽  
pp. 1469-1482 ◽  
Author(s):  
Andy Golden ◽  
Penny L. Sadler ◽  
Matthew R. Wallenfang ◽  
Jill M. Schumacher ◽  
Danielle R. Hamill ◽  
...  
Keyword(s):  
Eukaryotic Cell ◽  
Temperature Sensitive ◽  
Anaphase Promoting Complex ◽  
C Elegans ◽  
Antibody Staining ◽  
Polar Bodies ◽  
Phosphohistone H3 ◽  
M Phase ◽  
Germline Proliferation ◽  
Meiosis I

The metaphase to anaphase transition is a critical stage of the eukaryotic cell cycle, and, thus, it is highly regulated. Errors during this transition can lead to chromosome segregation defects and death of the organism. In genetic screens for temperature-sensitive maternal effect embryonic lethal (Mel) mutants, we have identified 32 mutants in the nematode Caenorhabditis elegans in which fertilized embryos arrest as one-cell embryos. In these mutant embryos, the oocyte chromosomes arrest in metaphase of meiosis I without transitioning to anaphase or producing polar bodies. An additional block in M phase exit is evidenced by the failure to form pronuclei and the persistence of phosphohistone H3 and MPM-2 antibody staining. Spermatocyte meiosis is also perturbed; primary spermatocytes arrest in metaphase of meiosis I and fail to produce secondary spermatocytes. Analogous mitotic defects cause M phase delays in mitotic germline proliferation. We have named this class of mutants “mat” for metaphase to anaphase transition defective. These mutants, representing six different complementation groups, all map near genes that encode subunits of the anaphase promoting complex or cyclosome, and, here, we show that one of the genes, emb-27, encodes the C. elegans CDC16 ortholog.

scholarly journals Multiple Subunits of the Caenorhabditis elegans Anaphase-Promoting Complex Are Required for Chromosome Segregation During Meiosis I

Genetics ◽  
2002 ◽  
Vol 160 (2) ◽  
pp. 805-813 ◽  
Author(s):  
Edward S Davis ◽  
Lucia Wille ◽  
Barry A Chestnut ◽  
Penny L Sadler ◽  
Diane C Shakes ◽  
...  
Keyword(s):  
Rna Interference ◽  
Caenorhabditis Elegans ◽  
Chromosome Segregation ◽  
Sister Chromatid ◽  
Sister Chromatid Cohesion ◽  
Anaphase Promoting Complex ◽  
Genetic Screens ◽  
Chromatid Cohesion ◽  
Interference Studies ◽  
Meiosis I

Abstract Two genes, originally identified in genetic screens for Caenorhabditis elegans mutants that arrest in metaphase of meiosis I, prove to encode subunits of the anaphase-promoting complex or cyclosome (APC/C). RNA interference studies reveal that these and other APC/C subunits are essential for the segregation of chromosomal homologs during meiosis I. Further, chromosome segregation during meiosis I requires APC/C functions in addition to the release of sister chromatid cohesion.

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