scholarly journals Spherical spindle shape promotes perpendicular cortical orientation by preventing isometric cortical pulling on both spindle poles during C. elegans female meiosis

Development ◽  
2019 ◽  
Vol 146 (20) ◽  
pp. dev178863 ◽  
Author(s):  
Elizabeth Vargas ◽  
Karen P. McNally ◽  
Daniel B. Cortes ◽  
Michelle T. Panzica ◽  
Brennan M. Danlasky ◽  
...  
Keyword(s):  
Female Meiosis ◽  
C Elegans ◽  
Spindle Poles

scholarly journals Katanin controls mitotic and meiotic spindle length

2006 ◽  
Vol 175 (6) ◽  
pp. 881-891 ◽  
Author(s):  
Karen McNally ◽  
Anjon Audhya ◽  
Karen Oegema ◽  
Francis J. McNally
Keyword(s):  
Chromosome Segregation ◽  
Eukaryotic Cell ◽  
Meiotic Spindle ◽  
Mitotic Spindles ◽  
Wild Type ◽  
Female Meiosis ◽  
C Elegans ◽  
Microtubule Severing ◽  
Spindle Poles ◽  
Type C

Accurate control of spindle length is a conserved feature of eukaryotic cell division. Lengthening of mitotic spindles contributes to chromosome segregation and cytokinesis during mitosis in animals and fungi. In contrast, spindle shortening may contribute to conservation of egg cytoplasm during female meiosis. Katanin is a microtubule-severing enzyme that is concentrated at mitotic and meiotic spindle poles in animals. We show that inhibition of katanin slows the rate of spindle shortening in nocodazole-treated mammalian fibroblasts and in untreated Caenorhabditis elegans meiotic embryos. Wild-type C. elegans meiotic spindle shortening proceeds through an early katanin-independent phase marked by increasing microtubule density and a second, katanin-dependent phase that occurs after microtubule density stops increasing. In addition, double-mutant analysis indicated that γ-tubulin–dependent nucleation and microtubule severing may provide redundant mechanisms for increasing microtubule number during the early stages of meiotic spindle assembly.

scholarly journals Evidence for anaphase pulling forces during C. elegans meiosis

2020 ◽  
Vol 219 (12) ◽  
Author(s):  
Brennan M. Danlasky ◽  
Michelle T. Panzica ◽  
Karen P. McNally ◽  
Elizabeth Vargas ◽  
Cynthia Bailey ◽  
...  
Keyword(s):  
Spindle Pole ◽  
Outer Face ◽  
Chromosome Movement ◽  
Female Meiosis ◽  
Homologous Chromosomes ◽  
C Elegans ◽  
Spindle Poles ◽  
Pulling Forces ◽  
Spindle Elongation ◽  
Anaphase B

Anaphase chromosome movement is thought to be mediated by pulling forces generated by end-on attachment of microtubules to the outer face of kinetochores. However, it has been suggested that during C. elegans female meiosis, anaphase is mediated by a kinetochore-independent pushing mechanism with microtubules only attached to the inner face of segregating chromosomes. We found that the kinetochore proteins KNL-1 and KNL-3 are required for preanaphase chromosome stretching, suggesting a role in pulling forces. In the absence of KNL-1,3, pairs of homologous chromosomes did not separate and did not move toward a spindle pole. Instead, each homolog pair moved together with the same spindle pole during anaphase B spindle elongation. Two masses of chromatin thus ended up at opposite spindle poles, giving the appearance of successful anaphase.

scholarly journals Spherical Spindle Shape Promotes Perpendicular Cortical Orientation by Preventing Isometric Cortical Pulling on both Spindle Poles during C. elegans Female Meiosis

2019 ◽  
Author(s):  
Elizabeth Vargas ◽  
Karen P. McNally ◽  
Daniel B. Cortes ◽  
Michelle T. Panzica ◽  
Amy Shaub-Maddox ◽  
...  
Keyword(s):  
Polar Body ◽  
Spherical Shape ◽  
Viscous Drag ◽  
Female Meiosis ◽  
C Elegans ◽  
Microtubule Severing ◽  
Perpendicular Orientation ◽  
Spindle Poles ◽  
Meiotic Spindles ◽  
Segregation Of Chromosomes

AbstractMeiotic spindles are positioned perpendicular to the oocyte cortex to facilitate segregation of chromosomes into a large egg and a tiny polar body. In C. elegans, spindles are initially ellipsoid and parallel to the cortex before shortening to a spherical shape and rotating to the perpendicular orientation by dynein-driven cortical pulling. The mechanistic connection between spindle shape and rotation has remained elusive. Here we used mutants of the microtubule-severing protein katanin to manipulate spindle shape without eliminating cortical pulling. In a katanin mutant, spindles remained ellipsoid, had pointed poles and became trapped in either a diagonal or a parallel orientation. Results indicated that astral microtubules emanating from both spindle poles initially engage in cortical pulling until microtubules emanating from one pole detach from the cortex allowing pivoting of the spindle. The lower viscous drag experienced by spherical spindles prevented recapture of the cortex by astral microtubules emanating from the detached pole. In addition, maximizing contact between pole dynein and cortical dynein stabilizes round poles in a perpendicular orientation. Spherical spindle shape can thus promote perpendicular orientation by two distinct mechanisms.

Chromosome Segregation in C. Elegans Female Meiosis is Accompanied by a Switch in Lateral to End-On Microtubule Orientation

2018 ◽  
Author(s):  
Stefanie Redemann ◽  
Ina Lantzsch ◽  
Norbert Lindow ◽  
Steffen Prohaska ◽  
Martin Srayko ◽  
...  
Keyword(s):  
Chromosome Segregation ◽  
Female Meiosis ◽  
Microtubule Orientation ◽  
C Elegans

scholarly journals BUB-1 targets PP2A:B56 to regulate chromosome congression during meiosis I in C. elegans oocytes

2020 ◽  
Author(s):  
Laura Bel Borja ◽  
Flavie Soubigou ◽  
Samuel J.P. Taylor ◽  
Conchita Fraguas Bringas ◽  
Jacqueline Budrewicz ◽  
...  
Keyword(s):  
Kinase Domain ◽  
Meiotic Spindle ◽  
Dependent Manner ◽  
Female Meiosis ◽  
Linear Motif ◽  
Interaction Domain ◽  
C Elegans ◽  
Chromosome Congression ◽  
B Subunits ◽  
Meiosis I

ABSTRACTProtein Phosphatase 2A (PP2A) is an heterotrimer composed of scaffolding (A), catalytic (C), and regulatory (B) subunits with various key roles during cell division. While A and C subunits form the core enzyme, the diversity generated by interchangeable B subunits dictates substrate specificity. Within the B subunits, B56-type subunits play important roles during meiosis in yeast and mice by protecting centromeric cohesion and stabilising the kinetochore-microtubule attachments. These functions are achieved through targeting of B56 subunits to centromere and kinetochore by Shugoshin and BUBR1. In the nematode Caenorhabditis elegans (C. elegans) the closest BUBR1 ortholog lacks the B56 interaction domain and the Shugoshin orthologue is not required for normal segregation during oocyte meiosis. Therefore, the role of PP2A in C. elegans female meiosis is not known. Here, we report that PP2A is essential for meiotic spindle assembly and chromosome dynamics during C. elegans female meiosis. Specifically, B56 subunits PPTR-1 and PPTR-2 associate with chromosomes during prometaphase I and regulate chromosome congression. The chromosome localization of B56 subunits does not require shugoshin orthologue SGO-1. Instead we have identified the kinase BUB-1 as the key B56 targeting factor to the chromosomes during meiosis. PP2A BUB-1 recruits PP2A:B56 to the chromosomes via dual mechanism: 1) PPTR-1/2 interacts with the newly identified LxxIxE short linear motif (SLiM) within a disordered region in BUB-1 in a phosphorylation-dependent manner; and 2) PPTR-2 can also be recruited to chromosomes in a BUB-1 kinase domain-dependent manner. Our results highlight a novel, BUB-1-dependent mechanism for B56 recruitment, essential for recruiting a pool of PP2A required for proper chromosome congression during meiosis I.

scholarly journals Mixing and Matching Chromosomes during Female Meiosis

Cells ◽  
2020 ◽  
Vol 9 (3) ◽  
pp. 696
Author(s):  
Thomas Rubin ◽  
Nicolas Macaisne ◽  
Jean-René Huynh
Keyword(s):  
Female Meiosis ◽  
Homologous Chromosomes ◽  
C Elegans ◽  
Similarities And Differences ◽  
Segregation Of Chromosomes

Meiosis is a key event in the manufacturing of an oocyte. During this process, the oocyte creates a set of unique chromosomes by recombining paternal and maternal copies of homologous chromosomes, and by eliminating one set of chromosomes to become haploid. While meiosis is conserved among sexually reproducing eukaryotes, there is a bewildering diversity of strategies among species, and sometimes within sexes of the same species, to achieve proper segregation of chromosomes. Here, we review the very first steps of meiosis in females, when the maternal and paternal copies of each homologous chromosomes have to move, find each other and pair. We explore the similarities and differences observed in C. elegans, Drosophila, zebrafish and mouse females.

scholarly journals The Caenorhabditis elegans Homologue of Deleted in Azoospermia Is Involved in the Sperm/Oocyte Switch

2006 ◽  
Vol 17 (7) ◽  
pp. 3147-3155 ◽  
Author(s):  
Muneyoshi Otori ◽  
Takeshi Karashima ◽  
Masayuki Yamamoto
Keyword(s):  
Caenorhabditis Elegans ◽  
Caenorhabditis Briggsae ◽  
Essential Factor ◽  
Female Meiosis ◽  
Stem Cell Proliferation ◽  
C Elegans ◽  
Essential Step ◽  
Deleted In Azoospermia ◽  
Translational Regulators ◽  
Daz Gene

The Deleted in Azoospermia (DAZ) gene family encodes putative translational activators that are required for meiosis and other aspects of gametogenesis in animals. The single Caenorhabditis elegans homologue of DAZ, daz-1, is an essential factor for female meiosis. Here, we show that daz-1 is important for the switch from spermatogenesis to oogenesis (the sperm/oocyte switch), which is an essential step for the hermaphrodite germline to produce oocytes. RNA interference of the daz-1 orthologue in a related nematode, Caenorhabditis briggsae, resulted in a complete loss of the sperm/oocyte switch. The C. elegans hermaphrodite deficient in daz-1 also revealed a failure in the sperm/oocyte switch if the genetic background was conditional masculinization of germline. DAZ-1 could bind specifically to mRNAs encoding the FBF proteins, which are translational regulators for the sperm/oocyte switch and germ stem cell proliferation. Expression of the FBF proteins seemed to be lowered in the daz-1 mutant at the stage for the sperm/oocyte switch. Conversely, a mutation in gld-3, a gene that functionally counteracts FBF, could partially restore oogenesis in the daz-1 mutant. Together, we propose that daz-1 plays a role upstream of the pathway for germ cell sex determination.

scholarly journals PCMD-1 bridges the centrioles and the PCM scaffold in C. elegans

2020 ◽  
Author(s):  
Lisa Stenzel ◽  
Judith Mehler ◽  
Alina Schreiner ◽  
Sim Üstüner ◽  
Elisa Zuccoli ◽  
...  
Keyword(s):  
Protein Interactions ◽  
Coiled Coil ◽  
Protein Protein Interactions ◽  
Animal Cells ◽  
C Elegans ◽  
Mitotic Kinase ◽  
Spindle Poles ◽  
Pericentriolar Material ◽  
Translocation Assay ◽  
Assembly Proteins

ABSTRACTCorrect cell division relies on the formation of a bipolar spindle. In animal cells, microtubule nucleation at the spindle poles is facilitated by the pericentriolar material (PCM), which assembles around a pair of centrioles. Although centrioles are essential for PCM assembly, proteins that anchor the PCM to the centrioles are less known. Here we investigate the molecular function of PCMD-1 in bridging the PCM and the centrioles in Caenorhabditis elegans.We demonstrate that centrosomal recruitment of PCMD-1 is dependent on the outer centriolar protein SAS-7. While the most C-terminal part of PCMD-1 is sufficient to target it to the centrosome, the coiled-coil domain promotes its accumulation by facilitating self-interaction. We reveal that PCMD-1 is bridging the centrioles and PCM scaffold through protein-protein interactions with the PCM scaffold protein SPD-5, the mitotic kinase PLK-1 and the centriolar protein SAS-4. Using an ectopic translocation assay, we show that PCMD-1 is able to selectively recruit downstream PCM scaffold components to an ectopic location in the cell, indicating that PCMD-1 is sufficient to anchor the PCM scaffold proteins to the centrioles. Our work suggests that PCMD-1 is an essential functional bridge between the centrioles and the PCM.

A requirement for the Abnormal Spindle protein to organise microtubules of the central spindle for cytokinesis inDrosophila

2002 ◽  
Vol 115 (5) ◽  
pp. 913-922 ◽  
Author(s):  
Maria Giovanna Riparbelli ◽  
Giuliano Callaini ◽  
David M. Glover ◽  
Maria do Carmo Avides
Keyword(s):  
Spindle Pole Body ◽  
Spindle Pole ◽  
Male Meiosis ◽  
Wild Type ◽  
Female Meiosis ◽  
Central Spindle ◽  
Spindle Poles ◽  
Late Anaphase ◽  
Mutant Cells ◽  
Sperm Aster

Drosophila abnormal spindle (asp) mutants exhibit a mitotic metaphase checkpoint arrest with abnormal spindle poles, which reflects a requirement for Asp for the integrity of microtubule organising centres (MTOCs). In male meiosis, the absence of a strong spindle integrity checkpoint enables asp mutant cells to proceed through anaphase and telophase. However, the central spindle region is not correctly organised and cells frequently fail to complete cytokinesis. This contrasts with meiosis in wild-type males where at late anaphase a dense array of microtubules forms in the central spindle region that has Asp localised at its border. We speculate that Asp is associated with the minus ends of microtubules that have been released from the spindle poles to form the central spindle. A parallel situation arises in female meiosis where Asp not only associates with the minus ends of microtubules at the acentriolar poles but also with the central spindle pole body that forms between the two tandem spindles of meiosis II. Upon fertilisation, Asp is also recruited to the MTOC that nucleates the sperm aster. Asp is required for growth of the microtubules of the sperm aster,which in asp mutants remains diminutive and so prevents migration of the pronuclei.

scholarly journals C. elegans Nuclear Envelope Proteins Emerin, MAN1, Lamin, and Nucleoporins Reveal Unique Timing of Nuclear Envelope Breakdown during Mitosis

2000 ◽  
Vol 11 (9) ◽  
pp. 3089-3099 ◽  
Author(s):  
Kenneth K. Lee ◽  
Yosef Gruenbaum ◽  
Perah Spann ◽  
Jun Liu ◽  
Katherine L. Wilson
Keyword(s):  
Membrane Proteins ◽  
Nuclear Envelope ◽  
Integral Membrane Proteins ◽  
C Elegans ◽  
Nuclear Envelope Breakdown ◽  
Spindle Poles ◽  
Sds Page ◽  
Early Anaphase ◽  
Extraction Properties ◽  
Pore Complexes

Emerin, MAN1, and LAP2 are integral membrane proteins of the vertebrate nuclear envelope. They share a 43-residue N-terminal motif termed the LEM domain. We found three putative LEM domain genes inCaenorhabditis elegans, designated emr-1,lem-2, and lem-3. We analyzedemr-l, which encodes Ce-emerin, andlem-2, which encodes Ce-MAN1. Ce-emerin and Ce-MAN1 migrate on SDS-PAGE as 17- and 52-kDa proteins, respectively. Based on their biochemical extraction properties and immunolocalization, both Ce-emerin and Ce-MAN1 are integral membrane proteins localized at the nuclear envelope. We used antibodies against Ce-MAN1, Ce-emerin, nucleoporins, and Ce-lamin to determine the timing of nuclear envelope breakdown during mitosis in C. elegans. The C. elegans nuclear envelope disassembles very late compared with vertebrates and Drosophila. The nuclear membranes remained intact everywhere except near spindle poles during metaphase and early anaphase, fully disassembling only during mid-late anaphase. Disassembly of pore complexes, and to a lesser extent the lamina, depended on embryo age: pore complexes were absent during metaphase in >30-cell embryos but existed until anaphase in 2- to 24-cell embryos. Intranuclear mRNA splicing factors disassembled after prophase. The timing of nuclear disassembly in C. elegans is novel and may reflect its evolutionary position between unicellular and more complex eukaryotes.

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